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Koenig_and_Schultz_s_Disaster_Medicine_Ch_26.pdf

Explosive Events

John M. Wightman and Chetan U. Kharod

The opinions and assertions herein are the private views of the authors and are not to be construed as official or as reflecting the view of the United States government, Department of Defense, or Department of the Air Force. This is in part a government work. There are no restric- tions on its use.

OVERVIEW

Explosive events occur in many settings. They can have a variety of etiologies, which can be accidental or intentional. Many blasts damage only property, but every explosion can be classified as a potential injury-creating event (PICE).1 It is the human impact with which this chapter is mostly concerned. Injuries may occur to individuals or groups. Massive and multiple explosions may affect entire communities or larger regions, resulting in a disaster situation. According to Noji, “A disaster is defined as a natural or manmade event that results in an imbalance between the supply and demand for existing resources.”2

Most explosive events are unlikely to result in major catas- trophes, as defined by Lumley and Ryan, “where the social fabric of a society is disrupted and the medical infrastructure fails.”3

Some important exceptions exist, however. A single bombing of the only hospital in a region may cause temporary failure of that local healthcare system, until external resources can be mobilized. Multiple, intentional explosions specifically target- ing critical services may impact a larger population to a greater degree. A nuclear detonation would likely disable much of a city’s infrastructure. Volcanic eruptions have, and will again, create devastation on local, regional, national, and global levels.

Individual Impact

Blast injuries to persons encompass the full spectrum of poly- trauma. Individual physical injuries range from minor abrasions to “total body disruption” associated with wide scattering of multiple body parts. These are detailed under sections on patho- physiology and clinical care. Short- and long-term effects on survivors and their families can be devastating.

Not all blast casualties will require hospitalization. Many minimally injured victims may be discharged from the emer- gency department (ED) if they have appropriate social support and adequate access to the healthcare system. At the other end of the spectrum, some casualties will require intensive initial resus- citation and stabilization, multiple surgical procedures, ongoing physiological support, and management of any complications that develop. Hospitalization at a regional referral center is fre- quently necessary to bring together the many services essential for management of complex, multidisciplinary issues seen in victims surviving severe blast injuries.

Too often, the focus of healthcare attention is only on resus- citation, stabilization, and definitive medical and surgical care. Victims requiring hospitalization may also need prolonged reha- bilitation, physical therapy, and occupational therapy before returning, to some degree, to their preinjury lives. Even those blast-exposed individuals who may not even have entered the healthcare system through emergency medical services (EMS) or a hospital may need identification and follow-up services, particularly as regards to their mental health.

The psychological impact of any sudden traumatic event should not be overlooked. The importance of this underrec- ognized element of trauma management is beginning to receive attention in the lay press and the professional literature.4–7 Addi- tional information may found in Chapter 7.

Epidemiology

Very little has been written on the epidemiology of natural explo- sions. A computerized search of the medical literature regard- ing the Mount St. Helens volcanic blast of 1980 – the largest in the United States in the last century – revealed less than a dozen clinical articles covering medical and mental health con- sequences. Even as massive as this explosion was, only 57 people were reported dead or missing, likely due to a short but adequate warning time. Volcanic eruptions are discussed in more detail in Chapter 39.

The relative paucity of useful epidemiological information relative to blast injuries has been true of accidental and inten- tional explosions as well. One review of intentional bombings in

393 Koenig and Schultz's Disaster Medicine : Comprehensive Principles and Practices, edited by Kristi L. Koenig, and Carl H. Schultz, Cambridge University Press, 2009. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/apus/detail.action?docID=564432. Created from apus on 2018-03-08 08:55:45.

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394 ■ JO H N M. WI G H T M A N A N D CH E TA N U. KH A RO D

the United States (U.S.) reported limited information, but could draw no clinical conclusions because it was compiled from a law enforcement database.8 One complete report described all blast injuries in Finland over a 5-year period 1991–1995.9 Fireworks were the cause in 29%, explosive materials in 25%, and rupture of pressurized containers in 13%. Soft tissue injuries and burns were the most common injuries, but traumatic amputations and crushing injuries also occurred. Two victims for every 100,000 persons in the general population were admitted to the hospi- tal every year for an average of 11 days. An international list of major accidental explosions resulting in more than 100 fatali- ties occurring between 1906 and 1964 may be found in a review by Hamit.10 Most reports, however, are less comprehensive and describe casualties from individual events.11,12

One of the most detailed studies of an accidental indus- trial explosion was published after a series of blasts occurred at a petroleum plant in Pasadena, Texas, in 1989. Twenty-two victims were found dead at the scene and 131 casualties were transported to six area hospitals.12 Injuries to survivors were dominated by simple abrasions, contusions, and lacerations. The largest pro- portion of casualties was men 25–44 years old, likely because the initial explosion and subsequent fires mostly affected work- ers at the plant itself. Nonetheless, the three casualties not on the plant grounds were injured indirectly by blast effects up to 5 km away. Three-quarters of patients were treated and released from EDs. One admitted patient died, one was transferred to a rehabilitation facility, and all others were discharged home after 1–46 days as inpatients, although only three burn patients stayed longer than 3 days.

Accidental industrial blasts also occur in the manufacture of explosives.13 The use of fireworks, especially by nonprofessionals, has resulted in many injuries in many countries every year.14–18

In a U.S. study, boys 10–14 years old were found to be the popu- lation at highest risk, although 60% of all victims were older than 14 years.16 Injuries affected the hands, face, and eyes in order of descending frequency. Seven percent required hospitalization.

With regard to intentional bombings, numerous reports of individual incidents have appeared in the medical literature.19–43

Waterworth and Carr published two articles in 1975, which, when analyzed together, provided a picture of casualties from nearly simultaneous bombings inside two crowded public houses.22,23

One hundred casualties were either dead at the scene (18%) or managed at The General Hospital in Birmingham, England (82%). The overall mortality rate was 20%. Of the 82 reach- ing the hospital alive, 2.4% died during resuscitation. There were no late deaths. Approximately three of every four casualties were discharged from the ED. Ten of the 19 admitted patients (53%), excluding one patient sent directly to a burn unit, suf- fered superficial flash burns to 10%–50% of their body surface areas.

One of the first large case-series of civilian bombing victims was published by Rutherford in 1972.44 Hadden et al., extended this study at the same hospital.45 They described the injuries sustained by 1,532 consecutive patients seen at a single hospital in Belfast having an ED “with the capacity to accommodate up to 100 patients simultaneously” and availability of “all major surgical specialties.” Device sizes varied in equivalency from 1 to 90 kg of trinitrotoluene (TNT). Most of the 78 events generated 10 or fewer casualties reaching the hospital, but the range was 1–122 with approximately 10% of the incidents generating more than 20 patients at a time. The majority of victims managed in the hospital sustained abrasions, contusions, and lacerations

without internal injury. Approximately five of every six casualties were discharged from the ED, leaving 250 total patients admitted. Nine (3.6%) of these died, with most deaths being due to blunt or penetrating head or torso trauma. Four (0.3%) of all 1,532 patients required an emergent laparotomy with one patient also undergoing a thoracotomy. Fifty (3.4%) patients were burned, 33 of whom were admitted but none of the injuries necessitated skin grafting. Twenty casualties had traumatic amputations and four of them died. Forty other open extremity fractures were reported in an unknown number of patients.

The next large case-series from Northern Ireland was pub- lished by Pyper and Graham in 1983.46 They described the injuries sustained by 339 consecutive patients seen at a 200-bed hospital, which was located 48 km from Belfast and had just opened at the beginning of the study period. Device sizes were not reported. Consistent with previous articles, a large propor- tion of victims reaching the hospital sustained abrasions and lac- erations without internal injury. Slightly more than half (58%) of the casualties were discharged from the ED, leaving 142 total patients admitted. Five (3.5%) of these died, with most deaths due to head injury. Eight (2.4%) of all 339 patients required an emergent laparotomy. Two others underwent delayed laparo- tomies, both of whom died. Six (1.8%) patients were burned, and two of these required skin grafting. Twelve casualties had trau- matic amputations. Seventy-four other open extremity fractures were sustained by 35 patients.

In a report from Jerusalem the same year, Adler and coau- thors also published a case-series from a single hospital.47 They were the first to assign Abbreviated Injury Scale (AIS) scores and calculate an Injury Severity Score (ISS) for each of the 272 vic- tims they managed from 24 terrorist bombings over a 4.5-year period. The majority received minor injuries: 237 (87%) had an ISS 1–6; eight (3%) had an ISS 7–12; and 27 (10%) had an ISS 13–75. The authors noted that many ED charts were incomplete, so these data could be biased by casualty volumes or other non- medical factors. Of the 340 total patients received in the ED, 228 (67%) were discharged, 96 (28%) were admitted to the receiving facility, and 16 (5%) were transferred to a university medical center for specialty care. Only three hospitalized patients died. Eighteen abdominal operations were performed, but the urgency of these was not specified. Survivor duration of stays ranged up to 21 days.

Two separate events – each with two simultaneous inten- tional bombings – occurred in Istanbul on November 15 and 20, 2003.48 Ballistic injury was sustained by 86 and 93 victims on each of the 2 days, respectively. Two individuals on each day suf- fered intracranial injuries. The authors noted that inadequately controlling the scene resulted in a significant maldistribution of casualties to area hospitals. Approximately one in every six vic- tims was admitted to the hospital where they presented or were transferred to another facility.

Over the last few decades, prospective trauma registries have been established during and after extended conflicts, and the data they contain have been published. For encounters in Northern Ireland, the Hostile Action Casualty System was established to track injuries sustained by police and military personnel.49 A report of 828 of these casualties was published in 1989.50 The number of events was not reported, so rates could not be cal- culated. Nonetheless, some useful epidemiological information regarding types and severities of injury, particularly with regard to the effects of personal protective equipment ([PPE] i.e., body armor in these cases), could be ascertained.

Koenig and Schultz's Disaster Medicine : Comprehensive Principles and Practices, edited by Kristi L. Koenig, and Carl H. Schultz, Cambridge University Press, 2009. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/apus/detail.action?docID=564432. Created from apus on 2018-03-08 08:55:45.

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EX P LO S I V E EV E N TS ■ 395

Data from the Israel National Trauma Registry were used to publish the country’s experience with suicide bombers during the years 2000–2004.51 A total of 1,155 victims were studied, many injured by shrapnel intentionally placed around devices to cause extensive ballistic trauma. These casualties were compared with other trauma patients in the registry, although few details of the control group were provided in the article. Victims of sui- cide bombers were statistically more likely to require intubation, pleural decompression, resuscitative thoracotomy, and each of a variety of ancillary studies (e.g., plain radiography, ultrasound, computerized tomography, and arteriography) in the ED. As a result of a higher proportion of internal injuries requiring sur- gical intervention, they were also more likely than the control group to be sent directly to an operating theater.

Societal Impact

The events cited previously represent terrorist actions. They do not include blast injuries from land mines and more conven- tional warfare, which are certainly PICEs, but are beyond the scope of this chapter, as is the societal impact of war itself. It can be noted, however, that from the beginning of the Global War on Terrorism on October 7, 2001 through August 2, 2008, there were 161 deaths and 1,184 injuries from improvised explosive devices and conventional explosive munitions in Operation Enduring Freedom. In Operation Iraqi Freedom, casualties included 2,787 killed and 22,979 injuries due to explosive blasts. These numbers only report U.S. service members. They do not include military coalition partners, enemy combatants, and civilians. Measure- ment of the prior and ongoing impact to individual and collective societies is ongoing.

Unrelated to conventional warfare, intentional bombings remain common throughout the world. Over a 20-year period in the U.S. from 1983–2002, there were 21,237 explosive bomb- ings, 6,185 incendiary bombings, 7,581 attempted bombings, and 1,107 bombs that exploded prematurely during manufacture or before reaching the intended targets.8 The U.S. Department of Justice’s extensive database does not allow for much additional clinical analysis, however.52

The societal impact of one or more sudden traumatic events is difficult to measure. Perhaps the best examinations of the clinical epidemiology of a large explosion have come from the April 19, 1995 bombing of the Murrah Federal Building in Oklahoma City.32,53–69 This event created a paradigm shift in the conduct of disaster research.70,71 It was estimated that more than 400,000 people in the metropolitan area were affected in one manner or another.58 There were clearly adverse effects on the mental health of portions of the exposed population: injured survivors, families and acquaintances of those killed and injured, and people whose levels of fear and stress were heightened by the event.56–58,61–68 Long-term epidemiological studies follow- ing the events of September 11, 2001 are just beginning to appear in the medical literature. The affects of explosive events on local healthcare systems have been more frequently reported and will be discussed later.

STATE OF THE ART

Research into the mechanisms of blast injuries and their clin- ical evaluation and management has proceeded steadily over the last century, with important accelerations in periods of

wartime. Some information gained during World War II is just as relevant today, while more recent biochemical and imag- ing technologies with enhanced computing power and sophis- ticated mathematical modeling have allowed keener insights into pathophysiological mechanisms applicable to the world’s most recent wars. Kluger described four areas of essential knowledge for medical personnel: blast physics; injury patterns; triage; and “treating multiple patients with multidimensional injuries.”72

Physics

Understanding the physics of explosions enables anticipation of trauma in blast-exposed individuals, some of whom will have no immediate symptoms or external signs of injury. Basic com- prehension of the mechanistic forces involved will aid healthcare workers in identifying the full spectrum of blast injuries, espe- cially those that may initially be clinically occult.

Blast Waves Natural explosions and some industrial accidents occur when

gases confined under high pressure are suddenly released. Most intentional blasts are created by high-order or low-order explo- sives, both of which involve the rapid chemical conversion of a liquid or solid material into a gas of essentially equal num- bers of molecules in an equal volume. Low-order explosives burn rapidly to generate gas, whereas high-order explosives det- onate to create gas in nanoseconds. As a consequence, this newly formed gas with highly compacted molecules is under extreme pressure. The initial pressure generated by detonation of the high-order explosive, cyclotrimethylene trinitramine, the pri- mary ingredient in Composition C4, is typically greater than 30 GPa (4 × 106 psi). The power of an explosive is customarily normalized to an equivalent weight of TNT, because it is math- ematically related to its mass, but may be different for different substances.73,74

The molecules composing the newly formed high-pressure gas are forced away from each other at supersonic speeds. They push against and compress molecules in the surrounding atmo- sphere faster than baseline thermal motion can disperse them. This “stacking” generates a dense band of greatly compacted air or water, depending on the surrounding milieu. The energy of this band is propagated spherically away from the epicenter of the explosion as an impulse blast wave. Its leading edge, which is typically only a few millimeters thick, is called the blast front. Figure 26.1 shows the pressure–time relationships relative to a stationary point in space as an idealized blast wave passes.75 The positive-phase impulse represents the initial spike of overpressure as the blast front speeds past the reference point. Because explo- sive gases continue to expand from their origin, a negative-phase impulse of relative vacuum follows the positive-phase impulse. As its energy dissipates, a blast wave eventually deteriorates into a high-magnitude acoustic wave.76,77

High-order explosive detonations cause such a rapid increase in pressure at their blast fronts (hence, force generation from high pressure to low pressure) that their blast waves are also referred to as shock waves. Low-order explosives generally do not release suf- ficient energy fast enough to demonstrate the shattering effects of shock waves.77 Thermobaric and volumetric weapons, fuel- air explosives, and nuclear detonations create thicker blast waves, which tend to envelope objects after the initial shock effect of the blast front.78,79

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396 ■ JO H N M. WI G H T M A N A N D CH E TA N U. KH A RO D

PPI

NPI

PPI = positive-phase impulse; NPI = negative-phase impulse.

Figure 26.1. Estimated overpressure and underpressure as a mathematically idealized blast wave passes a fixed point in space with time on the x-axis and atmospheric pressure on the y-axis. Peak overpressure may be found at the apex of the pressure spike. This figure is in the public domain as a U.S. government work. It was reproduced from the Ann Emerg Med. 2001;37(6):664– 678.75

Pressure differentials between the blast front and the sur- rounding atmosphere also create net movement of molecules that generate a blast wind. Detonation of a high-order explosive causing a peak static overpressure of 35 kPa, which is just strong enough to rupture half of exposed tympanic membranes (TM),

may also generate a dynamic pressure sufficient to create wind speeds of 70 m/s.76 Although they only exist briefly, blast winds can propel objects and people considerable distances. The wind created by a blast sufficient to cause internal injury in a significant number of casualties may exceed 400 m/s.75

Internal Force Propagation When a blast front contacts an object, the band of high

pressure exerts a force on the object existing at relatively low pressure. This is called blast loading.76,80,81 This briefly applied but high-magnitude force creates an acceleration of the object’s surface to a peak velocity and maximal displacement, until the elasticity of the surface overcomes its inertia. This rapid surface acceleration induces an internal stress wave propagated into the object roughly parallel to the direction of the incident wave. Solid objects, such as building surfaces, tend to shatter under this stress. More compliant surfaces, such as those of the human body, tend to compress under the force then rebound to their former shape once the blast wave passes. The magnitude of the stress wave in animal tissues is proportional to the peak surface velocity.82 Figure 26.2 shows the relationships of acceleration, peak velocity, and internal pressure generation.76 Compression also creates tangential shear waves proportional to the degree of displacement as surfaces are stretched inward.83 When this rapid compression occurs at the chest wall, it develops too fast to allow internally increased air pressure to decompress through tracheal venting.76,81,83,84

–2.0 .0 2.0 4.0 6.0 8.0 10.0 –2.0 .0 2.0 4.0 6.0 8.0 10.0

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Figure 26.2. Mathematically predicted (solid lines) and experimentally measured (dashed lines) thoracic dynam- ics caused by blast loading after detonation of 2.2 kg of Composition C4 to the right side of a sheep: (A) acceleration of the right rib cage peaked near 200 km/s2; (B) velocity of the right rib cage peaked near 40 m/s; (C) pleural pressure under the right rib cage peaked more than 210 kPa (30 psi); and (D) airway pressure in the right lung exceeded 100 kPa (14 psi). This figure is in the public domain as published by the Office of the Surgeon General of the United States Army, Falls Church, Virginia, USA. Reproduced from the Textbook of Military Medicine. 1991:266.76

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EX P LO S I V E EV E N TS ■ 397

Pathophysiology

Mechanisms of internal organ injury following blast exposure are multifactorial but stress and shear on biological tissues may result in irreversible work being applied. Irreversible work can be thought of as overwhelming the elasticity (i.e., ability of a substance to return to its original shape) of a given tissue, thus causing damage in some ways similar to blunt trauma. The best analogy can be found in the Textbook of Military Medicine.

An aluminum beverage container that is pushed in only slightly will pop back to its original shape when the force is removed (and any work done by that force is recov- ered). The onset of damage occurs when the stress equals the tensile strength of the material. As the stress increases beyond the tensile strength, the work done by the excess external force will not be recovered.76

Although the precise internal force vectors applied and the exact tensile strengths of all biological tissues are not known, this con- cept can be used to support integrated finite-element modeling to predict injuries.76,85,86

On more of a macro scale, the concept of blast loading can be used to estimate the severity of injury. The Northern Ireland Hos- tile Action Casualty System was used to devise a table with five nonparametric groupings of charge weight against three group- ings of intervening distances.50 The calculated overpressures in pounds per square inch (1 psi = 6.895 kPa) were then clustered and tagged to descriptors of blast loading: less than 20 psi, minor; 20–50 psi, moderate; 50–80 psi, severe; and more than 80 psi, very severe. Of the 828 casualties registered in the years 1970– 1984, there were approximately equivalent numbers in each of these four groups. No casualty in the first three groups died of “severe chest injury alone . . . with no serious external injury,” whereas 17% of those with very severe blast loading fell into this category and presumably died of blast lung injury (BLI). Of the 42 patients who died in a hospital, 12 did so during the initial ED resuscitation and 14 during or shortly after an initial surgery. Half of the later deaths were due to severe head injury, and half were due to respiratory failure – whether from BLI, acute res- piratory distress syndrome (ARDS), or a combination of both could not be established with certainty.

The primary effects of blast overpressure tend to more severely affect air-containing structures of the body. Differen- tial velocities of stress waves traveling through water-density tis- sues and through air-density lumina create additional internal shear waves that can tear parenchyma at air–tissue interfaces.75

This can also occur at any location where a density transition is present.83

Injury Classification The trauma caused by explosive detonations has tradition-

ally been categorized by mechanism. Primary blast injury (PBI) is caused by the effects of the blast wave transmitting forces into the body. Secondary blast injuries are ballistic injuries from fragments, shrapnel, and debris energized by the explosion or associated blast wind. Tertiary blast injuries occur when people are displaced by forces of the blast front and blast wind and are thrown through the air, tumble along the ground, and impact objects.87 Other authors have added quaternary and quinary blast injuries, but these have not been standardized.88–91 The taxon-

Figure 26.3. TM ruptured by blast impulse. Note nearly complete loss of tissue, which will likely require grafting. Most ruptures will heal sponta- neously. Photograph courtesy of Dr. Bartolomé Scola, Head of ENT Service, University General Hospital Gregorio Marañón, Madrid, Spain. See color plate.

omy described by Stuhmiller is probably the most appropriate.86

He depicted quaternary injuries as those resulting directly from “all explosion-mediated injuries not associated with pressure or wind effects,” most notably thermal, toxic, and asphyxiant mech- anisms. Collateral injuries – such as crush from building collapse, fall from a height, motor vehicle crash, and so forth – encompass all other outcomes.

Obtaining a description of potential mechanisms of injury is important in the management of trauma victims, but these cate- gorizations are more useful when devising equipment and tactics related to injury prevention. Those caring for these patients sim- ply need to know that an explosion occurred, thus creating the possibility of PBI, and blastwind–mediated total body accelera- tion if not confined. Otherwise, with the exception of the unique entity of PBI, victims of explosions sustain thermal, penetrating, blunt, crush, toxic, and other injuries similar enough to nonblast mechanisms that medical personnel should be familiar with the pathophysiological results.75,92 Healthcare personnel just need to understand the myriad possibilities for injury occurring during a single split-second event.

Blast Auditory Injury (BAI) and Ocular Injury It has been estimated that 7–55 kPa (1–8 psi) is required

to rupture the human TM (Figure 26.3), whereas peak over- pressures from extremely loud acoustic waves are usually less than 0.3 kPa (0.04 psi).73,94 Small shock waves able to rupture some unprotected TMs in open air have approximately the same impulse magnitude as those barely capable of shattering auto- mobile safety glass, snapping utility poles, and cracking brick walls.95 The pars tensa is the region most frequently injured.96

Although much less common, fractures of individual ossicles and dislocations of their joints also occur.94,96–98 Disruption of the conductive chain, but not TM perforation alone, may have a protective effect on impulse damage to the inner ear.94,96

When inner ear injury does occur, it manifests as a stun- ning of receptor organs without long-term sequelae in most patients.94,97 Temporary hearing loss and tinnitus are common, the severity of which typically decreases at farther distances from

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398 ■ JO H N M. WI G H T M A N A N D CH E TA N U. KH A RO D

Table 26.1: Conditions Resulting from Disruption of Tissue Interfaces in Air-Containing Structures of the Torso

Chest Abdomen

Escape of air into lung parenchyma results in

traumatic pseudocyst into pleural space results in

pneumothorax into vasculature results in

systemic air embolism

Escape of blood into lung parenchyma results in

pulmonary contusion into pleural space results in

hemothorax into airways results in hemoptysis

Escape of air into bowel parenchyma results

in pneumointestinalis into peritoneal space results in

pneumoperitoneum into vasculature results in

portal air embolism

Escape of blood into bowel parenchyma results

in bowel-wall hematoma into peritoneal space results in

hemoperitoneum into bowel lumen results in GI

hemorrhage

GI = gastrointestinal

This information is in the public domain as published by the Center for Total Access, Fort Gordon, Georgia, USA. Adapted from the Special Operations Forces Medical Handbook. 2001:7−23.104

the explosion.99–101 Severe structural damage to the organ of Corti and permanent hearing loss may occur, however.97,98

Foreign material and penetrating eye injuries are com- mon after explosions.60 Ocular PBI has not yet been conclu- sively demonstrated, but was the suspected cause of a hyphema in one report.102 The management of penetrating and non- penetrating eye injuries is beyond the scope of this chapter, but ED management following suicide bombings has been studied.103

Healthcare providers should ask questions focused on visual and auditory symptoms.104 “Do you have pain or problems with your eyes or ears?” Any decreased vision should be assumed to be a penetrating foreign body or hyphema until proven oth- erwise. Ringing, roaring, or decreased hearing is common, but determination of the long-term effect on hearing will require detailed audiometric testing with serial follow-up evaluations. “What does your pain feel like?” Eye pain is typically severe, and blepharospasm may make thorough examination difficult. Ear pain caused by a ruptured TM is often sharp initially but wanes over time.

Blast Lung Injury (BLI) A variety of injuries may occur in the lungs due to tissue tear-

ing. Blood can leak into the parenchyma, into the pleural space, or into the airways. Air can leak into the tissues, into the pleural cavity, or into the circulatory system. Table 26.1 summarizes the conditions resulting from disruption of air–tissue interfaces in the chest.

The prototypical BLI is hemorrhage into the pulmonary tis- sues and small airways. This can range from subpleural petechiae to contusions of various shapes and sizes (Figure 26.4).99,105

The degree of damage is proportional to the peak chest wall velocity.106 Pulmonary lacerations can result in alveolar-venous fistulae and traumatic emphysema, if contained within the lung parenchyma, and hemopneumothoraces and bronchopleural fis- tulae, if involving the visceral pleura.

Figure 26.4. Spectrum of BLIs showing: (A) surviv- able localized areas of contusion following a rela- tively small blast impulse in a sheep model; and (B) fatal diffuse internal contusions and external lacera- tions from a battle casualty. These photographs are in the public domain as published by the Office of the Surgeon General of the United States Army, Falls Church, Virginia, USA. Reproduced from the Text- book of Military Medicine. 1991:276 and 228, respec- tively.76 See color plate.

Alveolar–venous communications can allow air to enter the pulmonary venous circuit, travel to the left heart, and be ejected as systemic air emboli. Organ infarction and death can occur within minutes.107 Air embolism can also occur follow- ing blunt or penetrating trauma.108 Bronchopleural fistulae can lead to unilateral or bilateral tension pneumothoraces.109 Both of these conditions can be rapidly and significantly exacerbated by positive-pressure ventilation (PPV).75,108 It has been suggested that the commencement of PPV has led to early deaths in initial survivors.110

Medical personnel should ask targeted questions of casualties who can speak.104 “Are you short of breath?” Dyspnea may indi- cate tension pneumothorax, hemopneumothorax, pulmonary contusion, or shock from hypoxia, hemorrhage, or systemic air embolism. “Do you have any chest discomfort?” Penetrating or blunt trauma, pneumothorax, and myocardial ischemia due to coronary air embolism can all cause chest pain. “What does your pain feel like?” Pain associated with pneumothorax will usu- ally be sharp and focal, lateral or central, typically aggravated by breathing until the lung is completely collapsed. Pain of pul- monary contusion is often described as dull and diffuse. Discom- fort may wax and wane with respirations. Bronchospasm or dif- ficulty expanding the chest may be described as tightness. Chest pain that seems consistent with an acute coronary syndrome may

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EX P LO S I V E EV E N TS ■ 399

Table 26.2: Severity Categories for Blast Lung Injury (BLI) Reported by Pizov et al., Which May Help Predict the Necessity for Use of Positive-Pressure Ventilation (PPV) and Positive End-Expiratory Pressure (PEEP)109

BLI Categorization

Mild Moderate Severe

Infiltrates on plain chest radiography

Unilateral Bilateral but asymmetrical Bilateral and diffuse

paO2/FiO2 ratio > 26.7 kPa (200 torr) 8.0–26.7 kPa (60–200 torr) < 8.0 kPa (60 torr)

Bronchopleural fistulae Absent Present

PPV requirement Unlikely for a respiratory problem Highly likely but conventional methods usually effective

Universal and unconventional methods often necessary

PEEP requirement <5 cm H2O if PPV required 5–10 cm H2O usually necessary >10 cm H2O if volume-controlled PPV still used

This table is in the public domain as a U.S. government work. Reproduced from the Ann Emerg Med. 2001;37(6):664–678.75

be due to air embolism of one or more coronary arteries. “How much effort is required to breathe?” Dyspnea at rest indicates shock due to external or internal hemorrhage or hypoxia due to airway obstruction, pneumothorax, or severe pulmonary contu- sion. The less exertion that leads to dyspnea, the more likely is BLI or pulmonary damage by another non-PBI mechanism.

Examination findings consistent with BLI include tachy- pnea; difficulty completing sentences in one breath; dry cough, with or without wheezing; hemoptysis of varying degrees; diminished breath sounds indicative of pulmonary contusion, pneumothorax, or hemothorax; inspiratory rales or dullness to percussion caused by interstitial edema, parenchymal hemor- rhage, or hemothorax; and poor chest wall expansion caused by decreased lung compliance.111,112 Rapid, shallow respirations are characteristic of BLI casualties.113

BLI is uncommon from terrorist bombings in open air civil- ian settings.114 Most victims close enough to high-order detona- tions to sustain BLI are killed by other blast mechanisms.50 In distinction, explosions in confined spaces, especially those pro- tected from significant secondary ballistic objects, create casualty populations with much higher proportions of survivors mani- festing BLI.28,115

Pooling data from two 1996 terrorist bombings inside enclosed buses in Jerusalem, Pizov and colleagues published a report on their observations regarding BLI severity.109 They were able to classify injuries into mild, moderate, and severe based on plain chest radiography, arterial blood gas analysis, and the pres- ence of bronchopleural fistulae. Contusion densities on chest radiographs ranged from localized unilateral to massive bilat- eral, whereas the paO2/FiO2 ratio (PFR) was utilized as a marker of lung injury impairing oxygen diffusion.

Wightman and Gladish combined this classification with information from other studies to create the correlates found in Table 26.2.75 Minor BLI, defined as one lung focally injured and a paO2 maintained above 5.6 kPa on an ambient FiO2 of 0.21, may require supplemental oxygen administration, but gen- erally will not require PPV for respiratory compromise. Victims may require PPV for other reasons such as decreased level of consciousness or the need for a surgical procedure requiring a general anesthetic. Moderate BLI, defined as most of one lung or both lungs involved asymmetrically and an inability to main- tain a paO2 of 13.3 kPa with a FiO2 of 0.5, normally requires

some period of volume-controlled ventilation using reasonable levels of positive end-expiratory pressure (PEEP) or pressure support. Severe BLI, defined as the inability to achieve a paO2

of 8.0 kPa with a FiO2 of 1.0, often requires pressure-controlled ventilation, inverse inspiratory/expiratory ratios, and permissive hypercapnia.

For out-of-hospital responders, Wightman used relation- ships in the oxygen–hemoglobin dissociation curve to esti- mate pulse oximetry (SpO2) measurements corresponding to the previous PFR categorizations. These recommendations assumed no major left or right curve shifts, no significant elevations in altitude, and no hemoglobin or mitochondrial toxin.104 Minor BLI would be defined as any SpO2 reading at or above 75% hemoglobin saturation on ambient air with an FiO2 of 0.21. Moderate BLI would be any reading at or above 90% on 100% supplemental oxygen. Severe BLI would be any reading less than 90% on the same.

Blast Intestinal Injury (BII) Table 26.1 summarizes the conditions resulting from disrup-

tion of air–tissue interfaces in the abdomen. When stress-induced pressure differentials cause tissue tearing of air-containing structures in the gastrointestinal (GI) tract, these organs can bleed into mesentery, the bowel wall, or into the lumen (Fig- ure 26.5). They can rupture, releasing air and GI contents into intrathoracic, intraperitoneal, or extraperitoneal spaces.98,105

The colon is the most common organ affected, likely because of its larger gas content.116,117 Tension pneumoperitoneum has been reported.118 PBI-induced esophageal rupture is extremely rare.

Targeted questions to ask casualties are similar to those for blunt abdominal trauma.104 “Do you have abdominal or testic- ular pain, nausea, urge to defecate, or blood in your stools?” BII may cause visceral, parietal, or referred pain. “What does your pain feel like?” Stretched bowel wall will feel like a per- sistent gas bubble with possibly sharp and crampy waves as it is affected by peristalsis. Once the bowel ruptures, pain often decreases until peritonitis begins. The pain of peritonitis is com- monly diffuse and severe and may be associated with a fever. The abdominal, flank, back, genital, perineal, and rectal examinations are the same as for any other polytrauma patient, although the probability of bowel rupture is comparatively higher. Moreover,

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Figure 26.5. BII from a sheep model. Note segmental parenchymal hemorrhage and intraluminal blood visible through other areas of relatively intact bowel wall. This figure is in the public domain as published by the Office of the Surgeon General of the United States Army, Falls Church, Virginia, USA. Reproduced from the Textbook of Mil- itary Medicine. 1991:288.76 See color plate.

problems can evolve over time as intestinal perforation can be delayed by several days following bowel wall injury without immediate rupture.119–121

Traumatic Brain Injury (TBI) Blast-induced traumatic brain injury (TBI), when neither

definitively blunt nor penetrating in nature, occurs in casual- ties, and ranges from severe to mild. The pathophysiology of damage is not well understood and often not apparent when using conventional imaging techniques. Putative mechanisms of primary TBI are likely a combination of gross acceleration, vas- cular surge, and electromagnetic pulse. Local biochemical and systemic metabolic derangements contribute.86,122 A long list of humoral and inflammatory mediators suspected of causing ultrastructural injury is generated by these pathophysiological mechanisms.

Blast-pressure forces applied to one side of the head microseconds before the other side can result in gross accel- eration until the blast front traverses the skull, when the head could be accelerated in the reverse direction. Simulations have shown that explosive blasts can cause accelerations exceeding the maximum survivable magnitude of 300 G (G = the force of grav- ity).86 Based on a sport injury model, 50 G may be the threshold for mild TBI.123 Coup and contre-coup trauma may be caused by localized regions of high pressure and relatively low pressure, which distort tissues to cause damage during head jerks.124,125

Axonal tension can affect neural activity.126

Compression of the torso, which is relatively more compli- ant than the skull, can force blood into the cranium, produc- ing a vascular surge that increases both pressure and volume resulting in dysfunction.86 Neuronal changes also occur in those

cells responsible for hearing and vision.127,128 Systemic derange- ments sustained in many serious traumatic events (e.g., hypoxia, hypotension) further compromise brain function and may lead to irreversible tissue damage.

Superheated gases created by high-order explosives that are under pressure at the blast front can charge atmospheric particles to generate an electromagnetic pulse.129 The resultant energy flux may adversely affect neural tissue.

In a 10-year study of accidental explosions seen at the Mary- land Institute for Emergency Medical Services Systems, more than one third of patients with a normal Glasgow Coma Scale score had some element of TBI missed on the initial evaluation.130

Questions can be used for rapid screening for potential neurolog- ical injury.104 “Do you have headache, vertigo, unsteadiness, or nausea?” This may help identify patients at risk for mild TBI and lead to initiation of casualty protection and medical management as early as possible. When time allows, the best screening tool currently available is the Military Acute Concussion Evaluation (MACE).131

Neurological deficits found on examination of blast victims may range from subtle dysfunction to complete unresponsive- ness. Causes of altered mental status or seizures include conven- tional blunt or penetrating head injury; stroke from cerebral air embolism; hypoxemia from lung injury; or shock from tension pneumothorax, hemorrhage, or air embolism–induced myocar- dial infarction or spinal cord dysfunction. Intracranial lesions resulting in focal deficits will most likely be due to cerebral or extraaxial hemorrhage. Visualization of air in retinal vessels, mottling of nondependent areas of skin, or demarcated tongue blanching are insensitive but specific indicators of systemic air embolism.132

Other Primary Blast Injuries A syndrome of bradycardia and hypotension without blood

loss has been described in blast-injured soldiers.133 Blast loads directed only toward the chest in animal models cause a unique, vagal nerve–mediated form of cardiogenic shock without com- pensatory vasoconstriction.134 This phenomenon occurs within seconds of exposure, and partially resolves over 1–2 hours. Pressure-sensitive pulmonary C-fiber receptors may be the initi- ating afferent limb of this reflex.135

Blast waves that gain access to the upper respiratory tract can cause pharyngeal, laryngeal, and tracheal petechiae and ecchy- moses. These findings may be consistent with sufficient blast loading to also cause BLI.136 Blast waves, however, do not cause BLI via an air pulse down the respiratory tract.133 BLI is caused by forces applied to the chest wall.

Blast loading can also damage solid organs through displace- ment of body surfaces, shear wave stretch, and acceleration at organ attachments. The heart and intraabdominal solid organs may sustain petechiae, contusions, lacerations, or rupture.98

Stress waves are not apparently as important, likely because of these organs’ relatively homogeneous densities.137 Mesen- teric, retroperitoneal, and scrotal hemorrhages have also been reported.98,105

The combination of stress wave–induced shattering of bone and subsequent blast wind can tear off all or portions of the extremities and the head. Isolated torsos were all that were found of many victims exposed to the detonation of 1 met- ric ton of TNT-equivalent explosives behind the U.S. Embassy in Nairobi, on August 7, 1998 (author’s personal observation). Decapitation is universally fatal, as are many proximal extremity

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traumatic amputations, but survival has been reported for the latter.50,138–141

Local Medical Responders

The destruction of structures and associated debris resulting from explosive blasts will hamper how well first responders can perform their initial actions. The threats of accidental or inten- tional secondary blasts; evolving hazards such as fire, smoke, toxic substances, and building collapse; and potential follow- up attacks with ballistic weapons can restrict local responders’ efforts to reach victims. Even when victims are located, single or combined threats can affect the speed and accuracy of clinical assessment prior to movement of patients out of these hazardous environments.

No matter how dangerous the rapid movement of blast vic- tims may seem, the risks of lingering in an area of recent explosive activity to stabilize victims more adequately may be greater than any risk associated with early rescue or transportation. Organi- zations assigned to first response should certainly anticipate the unique challenges of rapid evaluation, triage, initial treatment, and evacuation of individual or multiple blast victims.

Stein and Hirschberg have described four out-of-hospital management phases based on their experiences with terrorist bombings in Israel.142 The “chaotic phase” is characterized by ambulatory victims self-evacuating or being transported from the scene by well-meaning bystanders. No professional respon- ders have arrived, and no Incident Commander has assumed control of the situation. The “reorganization phase” begins with the arrival of law enforcement, fire/rescue, and EMS assets. Triage is performed and resources are allocated for the most seriously injured casualties. The “site-clearing phase” involves evacuation of known patients and thorough searches for missed victims. In urban settings in Israel, scenes are typically cleared in less than 3 hours. The “late phase” encompasses the time required for all victims suffering from blast-related injuries to present for care. Minimally injured casualties and those with medical or psy- chological complaints usually seek care within 1–2 days of the event.

Einav and coauthors have suggested three phases: rapid on- scene triage with a minimum of medical interventions; urgent evacuation of critically injured casualties to the nearest hospi- tal for resuscitation and stabilization; and transportation of all other casualties to more distant and presumably less-burdened facilities, so as not to overwhelm those closest to the scene.143 A fourth phase might be the redistribution of casualties from less capable hospitals to regional trauma or medical centers.

The Israeli experience in out-of-hospital responses to terror- ist attacks has been detailed by Singer et al.144 The first medical team that arrives does not provide care. Its primary function is scene assessment and communication to the Incident Com- mand. Key elements include 1) type of event, 2) estimated casu- alty numbers, 3) location(s) of casualties, 4) safe approach and evacuation routes, and 5) estimated time of first casualty arrival at the closest hospital. As the next medical teams arrive, they eval- uate and manage casualties as they find them. Larger responses would allow additional medical teams to be assigned to different geographical regions.

Human access, care, and evacuation (HACE) is a term coined by Mark Gebhart and James Gruenberg of the National Center for Medical Readiness (personal communication). The concept describes the situations faced by emergency responders in per-

forming their out-of-hospital duties after a call for help has been initiated and will serve as an outline for the next discussion.

Human Access The potentially unstable environment associated with explo-

sive blasts may limit search and rescue efforts. There is a dearth of best-practice recommendations for out-of-hospital responders; however, a few observations can be stated.

Significant rescue and response efforts always demand coor- dination among public safety agencies (e.g., emergency man- agement, fire/rescue, law enforcement, and public health). As such, the effort should be directed via application of the Incident Command System. Utility companies should be closely engaged to allow rapid response to situations that put rescuers at risk, such as ruptured pipelines or damaged power lines. Bomb squads or military explosive ordnance disposal teams may be required, if unexploded devices are discovered.

Explosions can cause collapse of buildings and other struc- tures. Access to trapped victims falls under the discipline of urban search and rescue (US&R).145 Delayed access may result in natural progression of pathophysiological processes, with more complications from blast manifesting prior to rescue or before medical personnel can make initial contact with the victim. Con- ditions unfamiliar to EMS providers may exist. Some exam- ples include confined-space hypoxia, hypercarbia, or restric- tion of ventilation; dust, smoke, or toxic inhalations; prolonged, and possibly irreversible, hemorrhagic shock; compartment and crush syndromes; dehydration; and even advanced wound infec- tions and sepsis. Delays in evacuation can similarly result in abnormally prolonged medical responder–patient contact time prior to extrication and evacuation for stabilization or definitive care at a hospital or alternate care site.

Collapse of smaller structures may result in larger propor- tions of victims surviving to hospital admission.36 With the col- lapse of larger structures, the outcome is less favorable, as was observed in those victims trapped inside the Murrah Federal Building in Oklahoma City. In that event, the relative risk of dying was more than 16 times greater in the collapsed portion than it was in other areas of the structure.32 The only fatality that did not occur as a direct result of the explosion was a rescuer who was struck in the head by a falling object.

Therefore, potential benefits and risks must always be care- fully assessed before any decisions on access and rescue are made. Safety is a prime function of the Incident Command System. Evolving sensor technologies may facilitate locating victims, and even assessing their physiological statuses, so decisions regarding responder risks can be better considered.

Field Triage Although triage is usually discussed in the context of a dis-

aster or mass casualty scenario, where inadequate resources exist to meet medical needs, triage occurs daily in medical settings around the world. It can be applied to any decision related to allocation of resources. In the field, it applies to all aspects of HACE.

Triage for Targeting relates to locating and accessing victims of an explosive blast. This may be made difficult by threats dis- cussed previously, debris or hazardous materials dispersed by the energy of the explosion and the blast wind, and the lack of provider technical expertise to enter collapsed structures or buildings on fire. Reconnaissance by aircraft may be helpful in assessing the area affected, but there is currently little in the way

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of best practices or technological solutions to support the process of victim location beyond rescuers conducting thorough on-the- ground searches. Assigning personnel assets to structures with the highest probability of containing salvageable victims should be coordinated through the Incident Command System. Exter- nal assistance in the form of specialized search-and-rescue teams and equipment may be necessary.

Triage for Treatment in the out-of-hospital setting involves sorting patients based on required medical interventions. This presumes that the patient requiring the most immediate life- saving interventions is the one who will be triaged to the highest priority category. There are a number of triage systems available for use in mass casualty settings (see Chapter 12). Simple Triage and Rapid Treatment (START) and Secondary Assessment of Victim Endpoint (SAVE) encompass one triage scheme com- monly used in the United States.146 JumpSTART is a system proposed for pediatric use.147 The Paediatric Triage Tape has gained some acceptance in Europe and South Africa.148,149

Internationally, there are other triage methodologies com- monly in use, such as Triage Sieve and Sort in the United King- dom and an algorithm created by CareFlight in Australia.150–152

One group attempted to apply these two systems retrospectively, as well as the START methodology, to the 2005 London terrorist bombings to assess performance.153 Although all three seemed to be equivalent, conclusions were severely hampered by missing data and small numbers of critically injured patients.

Move, Assess, Sort, and Send is a more recently published approach.154,155 Move Assess, Sort, and Send (MASS) requires victims to hear and understand rescuer commands. This may limit its utility for children, those who do not understand the language spoken, and those with hearing loss after a blast. The Sacco Triage Method has been advocated by some authors as an improvement to the START/SAVE method, because it takes into account resource constraints and uses expert consensus to model expected deterioration rates in casualties awaiting treat- ment.156,157 It is not currently in widespread use, likely because it is proprietary and requires a labor-intensive numerically scoring calculation for each of three parameters using a 0–4 scale and totaling the results. This sum is then used to categorize victims into groups with the following numerical ranges for organizing scene resource allocation: 0–4, 5–8, and 9–12. At the time of this writing, neither of these systems has been used in an actual disaster, so data supporting their efficacy are limited.

A recently published article has called for a national U.S. standard for disaster triage. A multidisciplinary consensus com- mittee supported by the U.S. Centers for Disease Control and Prevention (CDC) reviewed previously published triage meth- ods and suggested an approach it believes combines the best aspects of several of these systems. It was given the acronym SALT for Sort, Assess, perform Life-saving interventions, and Treatment/Transportation.158 No additional commentary or studies have been published on this new proposal to date.

Whichever methodology is applied, two facts are critical: the responders must be intimately familiar with the chosen tech- nique, and they must dynamically reassess patients and reassign categories to optimize victim benefit and allocation of resources. Casualty receivers must also be aware of the system or systems used in their communities, so they are prepared for the types of casualties that will require care in each triage category.

Most field triage systems divide casualties into some combi- nation of five categories (listed in order of priority): immediate, delayed, minimal, expectant, and dead.159 The Magen David

Adom (MDA) Israeli National EMS system uses three categories: urgent, nonurgent, and dead.42 The MDA has the advantage of being a nationwide network with centralized organization in a relatively small geographical area, but response systems in other communities could adopt a similar approach.

Immediate or urgent casualties are those for whom immedi- ate life-saving intervention is required. The resource(s) needed to save the life of any given casualty in this category are as vari- able as the conditions that cause the life-threatening conditions. When immediately available, and not anticipated to be needed elsewhere, most communities and cultures have an expectation that the necessary resources will be committed. If, however, these resources are not available in the time frame needed, cannot be obligated to a single patient, or must be redistributed to many patients (e.g., large supplies of fluid or blood or the time a med- ical provider can spend with a single patient); casualties in the immediate category might be reclassified into the expectant cat- egory (see later).

Other victims would be nonurgent in the Israeli system. Delayed casualties are categorized as such based on the triage officer’s brief assessment of who does not need immediate life- saving interventions, but who still has not had potentially life- threatening problems excluded. Minimal casualties are those believed to have conditions not requiring intervention during the mass casualty situation to prevent undue mortality, morbid- ity, or suffering.

Although the expectant category derives from medically aus- tere military settings with typically longer evacuation times, it may be necessary to use this designation in civilian settings when needs outstrip resources. Many EMS educators teach an approach to expectant casualties as if they are “expected” to die, or are oth- erwise labeled as “unsalvageable.” A better approach would be to “expect” reevaluation of these casualties, and possibly undertake more aggressive management once sufficient resources become available.

In a disaster situation where needs exceed resources, resus- citation should not be attempted on victims who are found or received dead. Specific examples of injuries that might warrant assignment to each of the other four categories are detailed in many textbooks and publications. Baker summarized those with military application.160

Undertriage refers to categorizing patients into a lower acuity category than their conditions warrant and risks excessive mor- bidity and mortality from delays in care.159 On the other hand, overtriage categorizes patients into higher acuity categories than necessary and commits resources that might be needed else- where. Such activity is postulated to lead to a linear relationship between the overtriage rate and mortality in the overall pop- ulation of critical casaulties.159,161,162 No evidence is available demonstrating this assertion, however. All publications to date on the subject describe only associations. It is equally valid to postulate that the strain of working at mass casualty events with higher mortality rates results in more overtriage. Because no studies currently exist demonstrating a cause and effect relation- ship, either interpretation is equally valid. Nonetheless, during resource-constrained responses, incorrect triage decisions may have far-reaching consequences on the community affected by the disaster.163

Triage for Transportation is less understood outside of the military. It should be self-evident that patients incapable of mov- ing themselves to treatment facilities will ultimately require evac- uation. Most of the world’s military organizations use triage to

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sort patients into categories for allocation of scarce transporta- tion resources. In the U.S. Army and Marine Corps, for example, “urgent” patients are those requiring a higher level of treatment within the next 2 hours. “Priority” patients are those who require additional treatment within 4 hours. “Routine” patients require movement within 24 hours, so this would rarely apply to a civilian disaster setting in the developed world. Nonetheless, significant constraints on the availability of evacuation assets, long dis- tances, and lack of suitable destinations may force consideration of this category. Civilian agencies also have the option of chang- ing the expected time frame (e.g., 6 or 12 hours, instead of 24 hours).

The Israeli MDA uses only “urgent” and “nonurgent” cate- gories to triage for treatment and transportation. In a paper that defined mass casualty incidents as those of “large enough scale to recruit most of the rescue teams . . . within a defined region, regardless of the actual number of casualties,” Einav and col- leagues examined evacuations from urban and rural scenes of terrorist bombings over a 2-year period.143 Approximately one in every five victims was deemed to be urgent. Of note, a few inci- dents were not related to explosions, and those that did result from blasts encompassed both open-air and closed-space deto- nations. Even in “large urban” areas, less than half of these critical casualties were evacuated to trauma centers, although most of the remainder were transported to other medical centers, rather than smaller hospitals. The majority of patients arrived at the closest facility, whether self-evacuated or transported by ambulance.

Ideally, critically injured casualties should be managed at trauma centers, when available.38 Children should be transported to hospitals with pediatric capabilities and expertise.164 Less crit- ical casualties should be dispersed to less burdened facilities far- ther away from the incident.144 Use of helicopters, which rep- resent high-value, low-density assets in any disaster response, must be carefully considered.165 Effective transportation sys- tems for critical casualties require significant community and regional preparedness before an event, but evacuation processes are made even more complex by ongoing threats following initial explosions.166 Difficult on-the-spot decisions must be made in determining the best mode of transportation (e.g., ambulance or nonmedical vehicle of convenience, ground or air) and best destination for casualties, who did not self-evacuate, based on triage category and specific injury types.

Out-of-Hospital Care Once patients are adequately accessed in a relatively safe envi-

ronment, the individual out-of-hospital care each victim receives should not be affected by the specifics of postblast settings. This is true as long as due consideration is given to the potential for exceeding available time, personnel, equipment, and supply resources. Civilian first responders should be aware of the tactical combat casualty care (TCCC or TC3) recommendations made in the military version of the Prehospital Trauma Life Support manual or other references that approach out-of-hospital care in postblast scenarios.167–169 These guidelines discuss appropri- ate care in high-threat, time-constrained, and resource-limited situations.

Mass casualty out-of-hospital care may require EMS providers to use techniques with which they are less familiar. Examples include use of methods other than direct pressure to control hemorrhage (because this action consumes medically trained personnel resources that may be more effective else- where). Exsanguinating extremity hemorrhage may necessitate

control with a proximal tourniquet, either by inflating a blood- pressure cuff or applying a prefabricated or field-expedient device.170 The use of tourniquets in recent wartime applications has shown that correctly placed extremity tourniquets may be the leading lifesaving device used by soldiers in combat.171–173

They may also have applications in disaster medicine, but utiliza- tion should meet specific criteria in the civilian setting.174 Not all clinicians agree with their applicability in a civilian health- care system.175–177 The speed and efficacy of various devices have been studied in detail.178 Clot-enhancing agents such as microporous polysaccharide microsphere, mineral zeolite, or poly-N-acetylglucosamine (chitosan) may be useful adjuncts, or applied primarily for truncal or proximal extremity wounds where tourniquets cannot be used.179

Although rarely reported in the literature, massive hemopty- sis from severe BLI may compromise a victim’s airway. If simply allowing patients to attain their own best positions for oxygena- tion and ventilation is ineffective, rescuers must act by attempting to selectively intubate the least injured lung.75 In 99% of cases, a standard endotracheal tube passed orally to its full depth will cause the tip and balloon to sit in the right mainstem bronchus. After cuff inflation and a few ventilations, unilateral isolation should be assessed. If more blood passes around the tube than through the tube, then the right lung is protected from left-sided hemorrhage. If more blood passes through the tube, the right lung is likely the origin, and the left lung must be selectively intubated. This can be accomplished blindly using one of three maneuvers (Figure 26.6).180

Rescuers should permit victims to breathe spontaneously whenever possible.75 Increased airway pressure or decreased venous pressure exacerbates the risk of air entering the pul- monary venous circuit.181 The head should be kept at the level of the heart.132 When other injuries allow, casualties with unilat- eral blunt or penetrating chest trauma can be positioned on the side of injury to increase venous pressures.108 Victims with BLI might benefit from left semilateral decubitus or prone position- ing, but no studies have demonstrated efficacy.75 The left semi- lateral position (i.e., halfway between left-lateral and prone posi- tions) will place the coronary artery ostia in their lowest positions to decrease the likelihood of air entering these vessels.132 Prone positioning will place the left atrium at its highest point to poten- tially prevent air from passing through the mitral valve into the left ventricle and being ejected into the systemic circulation.75

Tension pneumothorax is common in BLI patients and may be bilateral.109 Rescuers must be taught to rapidly recognize the presentation of this condition and act quickly to prevent con- tinued hemodynamic compromise. The three potential indica- tions for emergent needle thoracentesis in the field are 1) uni- laterally decreased breath sounds and any clinical evidence of shock, 2) unilateral penetrating chest trauma and progressive (or already severe) respiratory distress, or 3) bilaterally decreased breath sounds in a moribund patient who is still attempting to breathe.

Intravenous access is indicated in most trauma patients; how- ever, fluid administration may not be required in all situations, especially those in which resources are relatively scarce. If external bleeding is controlled, and ongoing internal hemorrhage is not suspected, fluids are unnecessary in casualties who are not hemo- dynamically compromised, in shock, or unstable. Hypovolemic deterioration would not be expected without continued bleeding. Patients without ongoing hemorrhage, but clinically determined to be in shock, should be resuscitated with isotonic crystalloid

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YES

1. Position of comfort 2. Monitor 3. Nasopharyngeal airway

1. Coma position 2. Chin lift or jaw thrust 3. Cricothyroidostomy

Tube in less injured side 1. Secure tube in place 2. Assess need for ventilation 3. Auscultate for breath sounds

- Turn casualty’s head to right side - Rotate tube 180° so curve of tube pointing to casualty’s left side - Advance until only adapter shows out mouth 72% chance of success - Do not turn casualty’s head - Rotate tube 90° counter- clockwise so curve of tube pointing to casualty’s left side - Advance until only adapter shows out mouth 61% chance of success - Do not turn casualty’s head - Rotate tube 180° so bevel on opposite side - Advance until only adapter shows out mouth

Attempt selective intubation of left lung

92% chance of success

More blood around than

through tube?

Tube in more injured side

1. Auscultate for breath sounds

2. Use techniques for selective intubation of

opposite side

Attempt selective intubation of right lung

first 99% chance of success

- Pass endotracheal tube through cords - Advance until only adapter shows out

mouth

Major airway problem?

Massive hemoptysis?

More blood around than

through tube?

Pass endotracheal tube through cords to normal position

Withdraw or remove tube

based on volume of blood in lumen

Figure 26.6. Algorithm for blind selective mainstem intubation. This information is in the public domain as published by the Center for Total Access, Ft. Gordon, Georgia, USA. Adapted from the Special Operations Forces Medical Handbook. 2001:7–25.104

fluids to the point of shock reversal. Healthcare providers can administer fluids in 5-mL/kg boluses, thus theoretically min- imizing the impact on potentially damaged lungs. Vital signs should improve, but attaining normal values is not necessary. If external or internal bleeding cannot be expeditiously controlled, there is no point in administering crystalloid fluids. It is unlikely to be beneficial and may, in fact, be harmful.182

When responding to explosive events, civilian out-of- hospital medical personnel may inadvertently place themselves at risk for accidental or intentional injury. Under the military TCCC guidelines, the appropriateness of casualty assessment and field

treatment are based on the relative threat(s) to the medics. In mil- itary terminology, these are divided into “Care Under Fire” and “Tactical Field Care” situations.168,169 There is a third situation for evacuation from the battlefield, which will not be discussed in this chapter.

Scene security is of paramount importance during any response to prevent the responders from becoming casualties themselves. When the responders could be actively threatened by approaching the victim, it may not be appropriate to attempt rescue. Casualties who can move under their own power should be told to either move to cover or remain still, so as not to

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attract attention and become a target again. If a responder pro- ceeds to a casualty and is caught in a hazardous situation, most medical interventions would be inappropriate when both indi- viduals remained threatened. On the battlefield, care under fire is usually confined to control of rapidly exsanguinating external hemorrhage. Airway problems are rare, basic remedial maneu- vers require a constant position, and adjunctive interventions can be time consuming. If the responder moves to a position of cover, the casualty should be transported by field-expedient lifts, carries, or other available methods.

Tactical field care applies when medics are not experiencing an active threat, but close enough to danger to remain at risk. Table 26.3 lists civilian adaptations of the guidelines for battlefield interventions in these situations.167 Some items from the original recommendations were removed because civilian rescuers do not normally have access to a variety of medications carried by military operators and medics, and evacuation times to reach a treatment facility from a nontactical civilian setting are rarely as long.

Evacuation Local and regional protocols as well as existing disaster plans

should be the primary determinants of the modes of transporta- tion and patient destinations; however, the postblast environ- ment may warrant additional considerations. Experience has shown that many, if not most, disaster victims self-evacuate before the arrival of rescuers. This was true following the Tokyo sarin incident of March 20, 1995.183 It has also been noted in the aftermath of several accidental and intentional explosions.38,48,55

On the other hand, in 2004, following the almost-simultaneous detonations of high-order explosives in four commuter trains in Madrid, “the vast majority of survivors” were evacuated by ambulance.39 Walking times to area hospitals were not provided.

The intent of scene control and incident command with regard to evacuation is to determine the best destination for casualties, based on moment-to-moment clinical parameters matched to ever-changing capabilities and capacities of receiving facilities. In a 2-year study of evacuations from terrorism-related mass casualty incidents, one Israeli study found that most casual- ties were transported to the closest ED, despite centralized control of their EMS system.143

Unsecured scenes after an attack or the threat of accidental or intentional secondary explosions may preclude or seriously delay the use of civilian evacuation assets. Nonmedical vehicles of opportunity in the area of the explosion are sometimes used to transport victims to a safer nearby casualty collection point or all the way to a hospital. Waterborne evacuation is not often consid- ered, but, in certain locations, it may be an option during regional disaster planning and response. Factors that can prevent airborne evacuation of patients include scene safety considerations, nat- ural explosions (e.g., volcanic eruptions), or even poor weather conditions unrelated to the disastrous event. Aeromedical evac- uation will also require pilots and medical personnel to consider the effects of altitude on conditions such as hypoxemia, air embolus, pneumocephalus, ocular air after penetrating trauma, pulmonary pseudocyst, pneumothorax, pneumoperitoneum, and bowel injury.184 All of these can be worsened by decreased partial pressures of oxygen and reduced atmospheric pressures, the latter of which enables existing trapped air to expand.

Receiving medical facilities may be affected primarily by the event or their capacity secondarily degraded by inaccessibility, utility failures, or staff absenteeism. They may also be over-

whelmed by unusual patient volumes and severities in a disaster’s aftermath. This may be especially true for any specialty referral centers.

Specialized Responses

Some explosive events may necessitate additional considerations for local responders. Specialized teams with subject matter exper- tise and problem-specific training exist in many countries to assist local authorities and respond when requested. Incident managers must be aware of these external assets so they can request, coordinate, and oversee deployment of these resources within their jurisdictions.

Urban Search and Rescue Many victims injured in collapsed structures will be res-

cued by well-meaning bystanders.145 Nonetheless, it remains very important for the lay public, public safety professionals, and out- of-hospital medical personnel to understand the significant dan- gers involved in attempting to rescue victims trapped in collapsed structures. One of the first principles taught to first responders is scene safety. Untrained approaches to victim extrication run the risk of additional harm to existing casualties and turning would-be rescuers into additional casualties, thereby increasing the demand for rescue resources, while simultaneously decreas- ing the supply.

Professional US&R teams exist in many countries;145 how- ever, they are usually not plentiful and are often controlled by governmental organizations higher than the community level. For instance, U.S. federal US&R teams are unlikely to be avail- able to assist local rescuers in the first 3–4 days after an event, unless positioned in the region in advance of an anticipated event. On the other hand, many fire/rescue personnel around the world have been cross-trained in some of these specialized rescue techniques. Individuals may even serve on federal US&R teams in a reserve capacity. Some local fire departments or regional coalitions of departments have pooled resources to create their own formal US&R capabilities, which can be dispatched by local authorities.

Dirty Bombs Dirty bombs are any explosive device that intentionally

releases a secondary agent (e.g., chemical, biological, or radiolog- ical). Most people associate this term with radiological dispersion devices (RDDs) discussed in Chapter 30, but blast energy can be used to disseminate many hazardous or infectious materials. Management of chemical and biological casualties is discussed in Chapters 28 and 29.

RDDs, if constructed properly and used effectively, have the potential to pose a significant risk to an exposed population. Most plausible terrorism scenarios involve acquiring open-source iso- topes.185 These can either be disseminated with an explosion or delivered in manners similar to biological and chemical agents (e.g., contamination of food, distributed through ventilation sys- tems, and so forth). Internal contamination via inhalation or ingestion poses the greatest threat to health. Radioactive sources simply carried near or placed in the vicinity of people are called radiological exposure devices. These emanate ionizing radiation but generally do not cause radiological contamination.

Detection of an occult isotope release or covert attack is beyond the scope of this chapter; however, once identified, treatment of radiological casualties is possible (Chapter 30).

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Table 26.3: General Guidelines for Civilian Application of Tactical Combat Casualty Care in Threatening Situations

■ Casualties with an altered mental status should be disarmed immediately ■ Airway management

■ Unconscious casualty without airway obstruction ■ Chin-lift or jaw-thrust maneuver ■ Nasopharyngeal airway ■ Place casualty in recovery position

■ Casualty with airway obstruction or impending airway obstruction ■ Chin-lift or jaw-thrust maneuver ■ Nasopharyngeal airway ■ Allow conscious casualty to assume any position that best protects the airway, to include sitting up; or place unconscious casualty in

recovery position ■ If previous measures are unsuccessful, surgical cricothyroidotomy – induce local anesthesia with lidocaine, if conscious

■ Breathing ■ Consider tension pneumothorax and decompress with needle thoracostomy, if casualty has torso trauma and respiratory distress ■ Sucking chest wounds should be treated by applying a three-sided dressing during expiration and monitoring for development of tension

pneumothorax ■ Bleeding

■ Assess for unrecognized hemorrhage ■ Control all sources of bleeding ■ Use tourniquets for extremity hemorrhage, if necessary

■ Vascular access ■ Start an 18-gauge intravenous (IV) line or saline lock, if indicated (see text) ■ If resuscitation is required and IV access is not obtainable, use the intraosseous route

■ Fluid resuscitation ■ Assess for hemorrhagic shock: altered mental status in the absence of head injury and weak or absent peripheral pulses are the best field

indicators of shock ■ If not in shock

■ No IV fluids necessary ■ Oral fluids permissible, if conscious and evacuation delayed

■ If in shock ■ Hextend 500-mL IV bolus ■ If still in shock, repeat Hextend 500-mL IV bolus once after 30 minutes (no more than 1,000 mL Hextend)

■ If a casualty with TBI is unconscious and has no peripheral pulse, resuscitate to restore the radial pulse ■ Continued efforts to resuscitate must be weighed against logistical and the risk of incurring further casualties

■ Prevention of hypothermia ■ Minimize casualty’s exposure to the elements ■ Keep protective gear on or with the casualty, if feasible ■ Replace wet clothing with dry, if possible ■ Warm the casualty and prevent additional heat loss

■ If available: apply Ready-Heat blanket to torso; wrap in Blizzard Rescue Blanket; and put Thermo-Lite Hypothermia Prevention System Cap on the casualty’s head under helmet

■ If not available: use dry blankets, poncho liners, sleeping bags, body bags, or anything that will retain heat and keep the casualty dry ■ Apply additional interventions as needed/ available

■ Monitoring ■ Pulse oximetry should be available as an adjunct to clinical monitoring – though readings may be misleading in the settings of shock or

marked hypothermia ■ Inspect and dress known wounds ■ Check for additional wounds ■ Analgesia as necessary

■ Splint fractures and dislocations ■ Check distal neurovascular status before splinting ■ Check distal neurovascular status after splinting

■ Antibiotics, if available and evacuation is delayed ■ Communicate with the patient if possible

■ Reassure ■ Encourage ■ Explain care

■ Cardiopulmonary resuscitation ■ Resuscitation on the battlefield for victims of explosion injury or penetrating trauma who have no pulse, no ventilations, and no other signs

of life will not be successful and should not be attempted ■ Documentation

■ Clinical assessments, treatments rendered, and changes in casualty’s status ■ Forward this information with the casualty to the next level of care

Adapted with permission from Military Medicine: International Journal of the Association of Military Surgeons of the United States 2007;172(11 Suppl):1–19.168

406 Koenig and Schultz's Disaster Medicine : Comprehensive Principles and Practices, edited by Kristi L. Koenig, and Carl H. Schultz, Cambridge University Press, 2009. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/apus/detail.action?docID=564432. Created from apus on 2018-03-08 08:55:45.

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EX P LO S I V E EV E N TS ■ 407

Additionally, the U.S. Department of Health and Human Services has posted comprehensive information on the medical man- agement of radiation-exposed patients (http://www.remm.nlm .gov/). More information in the public domain can be obtained from the U.S. Armed Forces Radiobiology Research Institute’s Medical Management of Radiological Casualties handbook (free download available at http://www.afrri.usuhs.mil/outreach/pdf/ 2edmmrchandbook.pdf). For expert assistance, the U.S. Depart- ment of Energy maintains a worldwide 24/7 consultation capa- bility in its Radiation Emergency Assistance Center/Training Site (REAC/TS) (contact information is available at http://orise .orau.gov/reacts/). The U.S. Department of Defense supports a similar mission with its Medical Radiobiology Advisory Team (MRAT) (contact information is available at http://www.afrri .usuhs.mil/outreach/emergency response.html).

Nuclear Detonations Accidental or intentional nuclear detonation is a particularly

devastating disaster because it creates a combination of thermal, blast, and radiological injuries to a massive number of casual- ties in addition to major infrastructure destruction over a wide area. Blast wave overpressures from nuclear detonations may be orders of magnitude greater in amplitude than conventional high-order explosives and several meters thick with positive- phase impulses lasting seconds instead of milliseconds. These are expected to crush objects and people.186 Combined with an intense blast wind, disintegration or total body disruption usually occurs. Casualties of nuclear PBI are usually not salvage- able, even if found intact. Secondary and tertiary blast injuries are actually more important mechanisms of casualty genera- tion following nuclear detonations, because a greater percentage will initially survive than those affected by PBI. Prolonged blast overpressures can also result from fuel-air explosives, but these are unlikely to be acquired or delivered by nonmilitary groups. Nonetheless, some industrial accident scenarios may mimic their effects, with blast wave characteristics between those of nuclear devices and conventional high-order explosives.

As many as 80% of casualties directly injured by a nuclear detonation might have thermal trauma of various degrees either alone or in combination with blast or radiation injury.78 Mass burn care is by itself a daunting consideration for medical plan- ners and responders.187,188 Irrespective of concomitant radiation injury, no validated triage guidelines exist for such an event.189

The medical and surgical management of serious burn injury requires significant resources, even for a few individual victims (see Chapters 3 and 27).

Radiological injury manifests from either the prompt symp- toms of radiation exposure accompanying the detonation or the delayed symptoms from fallout of radioactive contamination. Nuclear detonations can be considered as collective radiological exposure devices/RDDs with similar but much more powerful and widespread effects. A standard fission device distributes its energy as approximately 5% initial radiation, 35% thermal, 50% blast, and 10% fallout radiation.78 Dispersed radioactive mate- rials may emit α- or β-particles, neutrons, or γ- or x-rays. The large number of casualties with combined injury patterns will profoundly affect triage decisions and the allocation of medical resources.

Following a nuclear detonation, the potential initial radiation dose decreases exponentially with distance from the device when exposure from subsequent fallout is excluded. Some physical

barriers may be protective, depending on the type of radiation and the materials and thickness of the shielding. Initial radiation doses less than 0.35 Gy will generally not cause early symptoms. Greater exposures will result in symptoms of the acute radiation syndrome (ARS) with time of onset inversely proportional to dose (see Chapter 30).

Delayed onset of nausea until 6–12 hours after a known event implies a relatively minor dose under 0.75 Gy. Higher doses may eventually cause the hematopoietic syndrome weeks later, but these doses can still be considered relatively minor if nausea is the only clinical manifestation. Vomiting or any systemic symptoms imply a dose exceeding 1.25 Gy, which has the potential to cause death in some exposed individuals. Diarrhea in the first 1–2 weeks implies the onset of the GI syndrome and receipt of a moderate dose over 3 Gy, which will kill at least 50% of the exposed population unless significant intensive care unit (ICU) resources can be allocated. Onset of the GI syndrome within the first day, when the time of exposure is known, indicates a more lethal level usually greater than 7 Gy. Neurological symptoms at any time signify severe radiation injury.190

Table 26.4 depicts one suggestion for alterations in standard triage practices when radiation injury may be a coexistent prob- lem.191 Severely exposed victims will all die, even with the most sophisticated medical care available. Therefore, all of these indi- viduals should be considered expectant in the context of a mass casualty situation. Palliative and pastoral care should be provided whenever possible. When resources are not limited, minimal additional care might be appropriate and culturally expected.

Victims with early onset of the GI syndrome should be considered expectant in a mass casualty situation, unless their conventional injuries are minimal. By definition of the term “minimal,” no excessive morbidity or mortality would be expec- ted to result from their nonradiation injuries, even if no pro- fessional care were rendered to them. Their radiation injury could then possibly be addressed later, if more resources become available.

Casualties with more severe conventional trauma and early radiation injury symptoms will have significant difficulty healing and be at much higher risk for infection than similarly injured casualties without radiation effects.191–193 When resources are scarce, their triage categories may require adjustment until they can be reassessed when more support might be available. Rapid onset of moderate ARS symptoms indicates a potentially lethal radiation dose, so immediate and delayed casualties should be considered expectant.

Prompt but minor radiation symptoms have the same effects on reparative and immunological responses, but usually indicate a sublethal radiation dose. Therefore, immediate and delayed conventional injuries could both be considered minimal, while casualties in the same categories without ARS symptoms are managed first. Once sufficient resources become available, subse- quent triage decisions could incorporate information regarding prognosis based on biological dosimetry (see Chapter 30).

“Probable” radiation exposure without rapid clinical man- ifestations is more problematic. Triage of minimal and expec- tant conventional injuries should remain unchanged in this circumstance. Due to the effects mentioned previously, however, immediate and delayed conventional injuries might be consid- ered delayed until biodosimetric information can be assessed. If radiation exposure is unlikely, no alterations to conventional triage categories are necessary, unless ARS manifests at a later

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Table 26.4: Priorities in Combined-Injury Mass Casualty Triage when Radiation Injury is Possible

Triage Category Based on

Change to Triage Category Based on Possibility of Coexistent Radiation Injury

Conventional Exposure Confirmed by Prompt

Clinical Manifestations Trauma Assuming No Coexistent Unlikely Probable Minor Moderate Severe Radiation Injury Exposure Exposure Symptoms Symptoms Symptoms

Immediate Immediate Delayed Minimal Expectant Expectant

Delayed Delayed Delayed Minimal Expectant Expectant

Minimal Minimal Minimal Minimal Minimal Expectant

Expectant Expectant Expectant Expectant Expectant Expectant

The information in this table is in the public domain as published by the Office of the Surgeon General of the United States Army, Falls Church, Virginia, USA. It was adapted – and slightly modified for civilian applications – from the Textbook of Military Medicine. 1989:45.191

time. Casualties with less likely but possible exposure must be followed closely for months to monitor for bone marrow suppression.

Local Medical Receivers

The most significant problems for receiving hospitals will be related to degraded capacity when victim needs exceed available resources. Staffing shortfalls and infrastructure failure must also be considered when facilities are directly affected by the event. Although Israel has had some success in redirecting patients seeking care for problems unrelated to the disaster, the majority of patients in most countries will still present with a variety of baseline conditions. The ability of hospitals to provide rapid and accurate screening of patients for such problems and refer them to other sources of care may enhance disaster operations at the receiving facility.

Primary Triage The ED is usually a hospital’s primary site for receiving

patients requesting unscheduled care. Thus, it is often desig- nated as the place where primary triage occurs following an off- site mass casualty event. As on any day, all presenting patients must be effectively screened for emergency conditions, including those due to the blast or explosion. Therefore, the ED staff or other designated team performing triage must be acutely aware of specific blast-related history and physical examination find- ings. This will facilitate early identification of less obvious clinical entities that may otherwise be missed. Some targeted questions to ask are suggested in the pathophysiology section of this chapter.

Part of primary triage’s function might be to relieve bottle- necks in the ED by dispersing casualties not requiring ED man- agement directly to other services within the hospital. For exam- ple, some immediate casualties, who may have had temporizing interventions in the field or at the primary triage location, could be sent directly to operating theaters or ICUs. Delayed casualties may be diverted to large receiving areas or sent directly to general medical wards for assessment by physicians and nurses stationed there. Although these healthcare providers may be less experi- enced with severe trauma, they should still have the training to evaluate blast-injured casualties for specific life-threatening problems that may develop over time. One study reported that patients admitted directly from triage were sent to the follow-

ing locations: 28% to an operating theater, 10% to an ICU, and 58% to a hospital ward.51 Another technique, which has been used during mass casualty situations in Israel, is to triage vic- tims with nonimmediate/nonurgent injuries away from the ED to other locations. Minor casualties could be seen at hospital or community clinics.

One of the major bottlenecks in mass casualty management of trauma victims is the need for radiological services. One pro- cess used in Israel is to send all casualties with nonimmediate soft tissue wounds to general medical wards for history-taking and physical examinations. If potentially serious delayed injuries are discovered, blood typing and possibly arterial blood gas analysis are generally the only laboratory studies necessary. Portable plain chest radiography could be performed on the wards, if equip- ment and technicians are not needed more urgently in the ED, ICU, and operating theater.

After all immediate patients are cleared from the ED, delayed patients can be brought back to the ED for expert reevaluation and any additional ancillary studies. Plain chest radiographs are important for most of these patients. Noncontrast computed tomography (CT) scanning has been utilized to screen all body areas of concern for blast, blunt, and penetrating trauma. Both are used to identify and localize foreign bodies created by debris, shrapnel, and bone fragments from a suicide bomber or other victim.194 Surgical decision making and ED dispositions can then be based on clinical examination and imaging results.

Emergency Care Injuries from explosions include penetrating, thermal, and

blunt mechanisms. Clinicians experienced in trauma manage- ment should be familiar with all of these. As such, only those considerations unique to blast injuries will be discussed in this chapter.

Massive hemoptysis will often require selective mainstem- bronchial intubation to protect the least injured lung from blood emanating from the opposite lung. This may be accomplished blindly as described for out-of-hospital care (Figure 26.6).180 It may also be sequestered by use of a double-lumen endotracheal tube or a Univent tube.195 In a situation in which significant resource constraints do not exist, resuscitative thoracotomy and isolation of the injured lung may be an option of last resort to save the victim’s life, if it can be determined from which bronchus the majority of the hemorrhage is emanating.

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BLI is relatively rare in survivors of large detonations occur- ring in an outdoor location.27,32,37 In open-air explosions, those close enough to the blast to develop significant BLI are usually dead at the scene.50,80 One notable exception was the terrorist bombing behind the U.S. Embassy in Nairobi, where BLI was a significant finding in victims. This was largely due to the truck detonating in a space surrounded by three multistory build- ings that reflected the blast wave multiple times.196 BLI is more commonly seen by medical providers when explosions occur in confined spaces.

Katz and colleagues were the first to publish the connection between confined spaces and increased incidence of BLI and BII in initial survivors.28 They reported on 55 casualties transported to two major medical centers in Jerusalem following detonation of a 6-kg device placed under a seat inside a commuter bus. Overpressures at various locations inside the bus were estimated at 385–527 kPa for 2–3 ms before the constraining windows and metal shell were blown away. Close to half of the casualties were evaluated and discharged from the ED. All 29 admitted patients had PBI of the ears, lungs, or bowel. For victims less severely injured but still admitted, there was a 29% (five of 21) incidence of BLI and a 10% (two of 21) incidence of “nonperforating bowel injury” (presumably BII). In casualties with more severe injuries, 75% (six of eight) had BLI and 25% (two of eight) had BII.

Pizov and colleagues pooled data from two similar explosions in commuter buses to report on their experiences with managing BLI.109 Forty-seven victims were found dead at the scenes and one more died on ED arrival. Of the 17 survivors, 15 (88%) had BLI. Nine (60%) had pneumothoraces, which were bilateral in seven. Five had clinically significant bronchopleural fistulae.

Patients with tension pneumothorax require needle thora- centesis followed by tube thoracostomy. Unilaterally decreased breath sounds and evidence of clinical shock should prompt immediate pleural decompression. Air escape without clinical improvement should raise suspicion for bronchopleural fistula, which may require more chest tubes, independent lung ventila- tion, or interventional surgery. In mass casualty scenarios, chest tubes before radiography have been recommended for any seri- ous thoracic injuries.142 If bilateral tension pneumothoraces have been ruled out in patients with blunt traumatic cardiac arrest, resuscitative thoracotomy should not be performed, because these casualties most often have unrecoverable BLI.142

Spontaneous, negative-pressure ventilation is preferred over PPV whenever possible.75,196 In a study of BLI patients admitted to the ICU at one Israeli medical center, 61% were intubated in the field or on arrival to the ED and 14% were intubated within 2 hours for progressive respiratory distress. The other 25% did not require mechanical ventilation.198 Noninvasive PPV has been used successfully to avoid endotracheal intubation in some patients.199 When invasive PPV becomes necessary, the initial use of PEEP up to 10 cm H2O is acceptable early in management.109

The need for more PEEP to maintain oxygenation should prompt a reassessment of ventilator mode.

Systemic arterial air embolism should be considered any- time a communication between the airways and the pulmonary venous circuit is suspected (e.g., hemoptysis).181 Yee et al., observed hemoptysis in approximately one of every six air embolism patients in a series of blunt and penetrating trauma.108

Infarction syndromes simultaneously affecting multiple organs may be noted on clinical examination.75,181 Left semilateral decu- bitus or prone positioning have theoretical but not proven ben- efits.75 Otherwise unexplained cardiac arrest might also suggest

Figure 26.7. Plain chest radiographs of blast-injured casualties show- ing: mild unilateral left-sided contusion. See color plate.

systemic air embolism. When managing individual cases (i.e., not in a resource-constrained setting) and the side of injury can be determined, resuscitative thoracotomy with hilar twist may be life saving.200

Optimal fluid management in patients with BLI is contro- versial, just as it is for pulmonary contusions due to blunt chest trauma.201 Colloids have been recommended over crystalloids for BLI, but outcome data are lacking.110 Following blunt trauma, neither the amount nor type of fluid seems to make a significant difference.202,203 Similar issues exist for blast and blunt TBI.75,204

Arterial blood gas analysis may be used to stratify patients into mild, moderate, and severe lung injury, regardless of whether they are due to blunt contusion, BLI, or ARDS (Table 26.2).75,109

The presenting PFR is predictive of outcome in blunt pulmonary contusion.202,203 Most other laboratory tests are unlikely to be of assistance in early identification or management of PBI.117,136,205

During mass casualty situations, individual facilities must deter- mine the appropriate application of their own laboratory proto- cols for blunt, penetrating, and thermal trauma.

A plain chest radiograph is mandatory in victims with any traumatic torso-related complaint. This may also be used to confirm endotracheal, thoracostomy, and gastric tube place- ments. The cardiac silhouette may be enlarged as a result of right heart overload from increased pulmonary vascular resistance due to significant BLI.19 Although almost any radiographic find- ing might have a conventional traumatic cause, manifestations of BLI include interstitial or alveolar fluid, hemothorax, pneu- mothorax, or pulmonary pseudocyst.19,206 Infiltrates consistent with pulmonary contusions are the most common parenchymal findings (Figure 26.7). Pulmonary injury severity can also be assessed radiographically (Table 26.2).109

Thoracic CT scanning may also be used to quantify interstitial and alveolar fluid and relate findings to ventilatory requirements of mild and severe categories similar to those reported by Pizov et al.109 In one report of patients with nonblast trauma, all those with more than 28% airspace filling required ventilatory assis- tance; none with 0% to 18% filling did.207 Transthoracic and transesophageal echocardiography have been used to image air bubbles transiting cardiac chambers.180

BII is generally uncommon, but perforation may be delayed up to 2 weeks after the event.208 Evaluation of individual patients should be similar to each institution’s protocols for blunt

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abdominal trauma, except clinicians should be aware that the pretest probability of bowel rupture will be higher, especially fol- lowing closed-space explosions.75 Based on literature from World War II and Israeli naval battles, BII is more common in victims exposed to underwater blasts.116,209 Fragments do not travel very far in water, but blast waves are propagated much greater dis- tances than they are in air. Individuals treading water or buoyed upright by a flotation device have no TM exposure, only partial thoracic exposure, and full abdominal exposure to underwater blast fronts. Hence, the abdomen receives proportionally greater blast loading.76,113

Focused assessment using sonography for trauma (FAST) scanning has been suggested as a rapid screening tool for intraperitoneal hemorrhage, whether or not combined with START triage methodology and screening images.75,142,210,211

Free intraperitoneal fluid, however, is not a common finding in intestinal perforation from any cause. CT scanning, especially without GI contrast material, is also not particularly sensitive in detecting bowel rupture. During mass casualty situations, some authorities have recommended that CT examination be reserved for diagnosing intracranial mass lesions during the initial phase of management – the period while casualties are still arriving.142

All blast-exposed individuals must be screened for TBI. The MACE is one useful tool, but no specific assessment methodology for brain dysfunction has proved superior in all settings. Even patients believed not to have TBI should be provided detailed instructions regarding the postconcussion syndrome and post- traumatic stress disorder, which may be more closely related to each other than previously suspected.

While BAI is not life threatening, it should be sought at some point during casualty evaluation. During mass casualty incidents, auditory and ocular injuries were the most frequently missed in one Israeli report.142 The ears should be examined by direct otoscopy. TM perforation, disruption of the ossicular chain, and gross contamination should be noted. Rupture and blood together could be indicative of TBI. In the absence of mul- tiple casualties, an otolaryngologist should be called to the ED or the patient should be seen within 1 day, if there is significant debris in the ear or the torn edges of the TM require realign- ment.212 Transient, intermittent, or permanent blast-induced vestibulopathy and dysequilibrium can occur.59

TM rupture may be a marker for TBI.213 It should certainly indicate exposure to blast overpressure, thus prompting mental status and neurological examinations. On the other hand, con- trary to previous expert opinions, the presence of TM rupture in patients without manifestations of BLI in the first hour after injury does not appear to be a surrogate marker of sufficient blast overpressure to produce delayed-onset BLI.214 The finding of oropharyngeal petechiae might, however.81,111 Absence of TM rupture makes BLI less likely but does not completely eliminate the possibility.75

Anesthesia and Surgery Older journal articles have suggested that patients with

BLI have poorer outcomes when operative procedures were required within a day after injury.19,133,209 This was presumed to result from PPV and inhalational anesthetic causing unrec- ognized pneumothoraces and bronchopleural fistulae to cre- ate tension pneumothoraces, or forcing air into the pulmonary vasculature to create systemic air emboli.209 Some experienced authors have recommended prophylactic chest tubes for any BLI patient undergoing surgery.111,112,197,215 Local, regional, and

spinal anesthetics were touted as preferred methods whenever possible.19,111,133,209 These complications seem less likely with modern monitoring equipment and might be mitigated further by an understanding of the risks and benefits of PPV.75,197 Thou- sands of surgeries have been performed on blast-injured casual- ties while they received general anesthetic agents during recent conflicts without known complications directly attributable to PPV.

Stein and Hirschberg have suggested dividing hospital-based surgical care into initial and definitive phases.142 The “initial phase” is the interval when casualties continue to arrive and the final number of patients is still unknown. They recom- mended that only the minimum acceptable level of care should be practiced during this period. Casualties categorized as imme- diate/urgent should be screened in the ED by personnel familiar with trauma management. Hemodynamically unstable patients should be emergently taken to an operating theater, if one is avail- able. Facility-wide blood use should be controlled by a senior surgeon. The “definitive phase” allows a more conventional approach to surgical management, once the total patient load is known and the operational status of current and surge resources has been assessed. Nonexsanguinating torso injuries should take precedence over fracture management, wound cleansing, debridement, and other minor procedures.

The surgical treatment of trauma can be significantly com- plicated by radiation exposure.193,216,217 All major surgical inter- ventions must be performed within the first 2 days, or be delayed months until late in the “convalescent phase” of ARS. There- fore, damage control, irrigation, and debridement of significant conventional wounds are normally conducted in this time win- dow. A “second look” procedure may be indicated, if performed within the following day or so. Any attempt at fracture healing or wound closure beyond this period, however, is likely to result in nonunion and dehiscence, respectively.

Intensive Care High ISSs characterize victims of terrorist bombings, who

often need critical care.208 In a study from Israel published in 2006, 26.6% of casualties from suicide bombers required ICU management compared with 6.7% of other trauma patients.51 In the detailed study by Pizov et al., examination of 15 BLI patients in ICUs found that only one could be managed without PPV, and eight (53%) required pressure-controlled ventilation or high- frequency jet ventilation.109 A more recent study from a different institution by Avidan et al., reported that seven of 28 (25%) BLI patients were managed without intubation.198 Permissive hyper- capnia has been recommended to keep transalveolar pressures less than 35–40 cm H2O, while still facilitating adequate oxy- genation.109,218 Nitric oxide inhalation has also been used.109,198

Extracorporeal membrane oxygenation has been suggested.214

Arterial air embolism is a rare but serious complication of BLI. It was suspected in only two cases of BLI patients admitted to Israeli ICUs over a 10-year period.198 One developed an acute electrocardiographic injury pattern and suffered cardiac arrest. The other developed a left hemiparesis without CT or mag- netic resonance imaging abnormalities. Both cases resolved with medical management. Details of treatment were absent, however, particularly with regard to hyperbaric oxygen therapy, which is the definitive treatment for air embolism after temporarily plac- ing the patient on 100% oxygen to wash out dissolved nitrogen. Transferring patients out of the ED or ICU to a hyperbaric cham- ber, or secondary transportation to another facility that offers this

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resource, can be a logistically difficult undertaking with a critical casualty.

Mass casualty situations may severely challenge ICUs with patients being sent directly from the ED, and postoperative patients requiring intensive care. According to a recent report by the American College of Chest Physicians’ Task Force for Mass Critical Care:

Most countries have insufficient critical care staff, med- ical equipment, and ICU space to provide timely, usual critical care to a surge of critically ill and injured vic- tims . . . many people with clinical conditions that are survivable under usual health-care system conditions might have to forgo life-sustaining interventions. Failure to provide critical care will likely result in high mortality rates.219

In situations of overwhelming casualty numbers, scarce resources must be justly allocated to provide only “essential care” for the greatest number of critical patients, rather than attempting to stretch existing or surge resources to deliver customary or “usual” treatment to all ICU patients.

It has been suggested that all hospitals with ICU capabilities be prepared to manage three times their normal capacities for a minimum of 10 days to be as prepared as reasonably possi- ble for any of several disaster events.220 The Sequential Organ Failure Assessment (SOFA) score may be a useful tool to esti- mate prognosis in ICU patients. It can assist triage decisions when allocating critical care resources after initial surge capacity has been maximized and patients have been secondarily redis- tributed between regional hospitals, but prior to the arrival of significant external assets.221

Additional Triage Secondary, tertiary, and subsequent triage decisions occur

at any point after primary triage. The first decision is where to send patients after initial evaluation and management in the ED or other location. Additional triage decisions could also involve transfer to regional centers. In nondisaster settings, specific cri- teria have been studied to determine the need for interfacil- ity transportation to a trauma center.222 Many countries have established regional referral centers to provide specialty services, which may not be offered at all hospitals (e.g., burn care, hyper- barics, neurosurgery, traumatology). Established transfer pat- terns may require revision under surge or crisis conditions at both sending and receiving facilities. When resource availability is exceeded, overwhelmed local hospitals will need to perform triage of patients to facilities designated by an Emergency Oper- ations Center (EOC) overseeing total community or regional resources. Depending on the capacity of those included in “nor- mal” referral patterns, transfer out of the affected area may be necessary. In the United States, this can be coordinated through the National Disaster Medical System (Chapter 9).

Contingency plans must be developed for community hos- pitals to manage patients provisionally until normal referral and transportation conditions can be reestablished. Disaster- induced surge operations and altered evacuation patterns will require healthcare professionals to adjust procedures. Referral centers should be prepared to increase capacity and to pro- vide extended consultative services by telecommunications or Internet to facilities with less capability or inability to transfer patients.

Figure 26.8. Multiple penetrating wounds of the lower extremities from ballistic projectiles following a suicide bombing. Photograph reprinted with permission of Lippincott Williams & Wilkins from Almogy G, Belzberg H, Mintz Y et al., Suicide bombing attacks: update and modifications to the protocol. Ann Surg. 2004;239(3):295– 303.35

Disposition Many patients with open wounds do not require hospi-

tal admission. Tetanus immunization status must be assessed, and updated if necessary; prophylactic antibiotic administration is often provided; and interventions for body-substance expo- sures from a suicide bomber or other victims are considered. Blood, bone, and other biological tissues can contact or pene- trate casualties – and these substances may be contaminated with infectious agents.223–225 The U.S. CDC has recommended strat- ifying casualties into three risk groups: 1) penetrating injuries or exposures to “nonintact” skin; 2) mucous membrane expo- sures; and 3) superficial exposure to intact skin.226 Within each of these risk categories, guidelines are discussed for hepatitis B and C viruses, human immunodeficiency virus, and Clostridium tetani. Despite published consensus recommendations from an authoritative source, the true risk is unknown, because no case of person-to-person disease transmission by this mechanism has been documented.

All open wounds are irrigated, yet few are debrided due to personnel constraints in mass casualty situations.227 Figure 26.8 shows the multiple penetrating wounds typical of secondary blast injury following bomb detonation. If, for example, only 10 casualties had 10 wounds each, then 100 wounds would require debridement. More casualties or more wounds per casu- alty would exponentially increase the workload. This could require allocation of surgical resources that might be better used in the operating theater for intracavitary injuries and open frac- tures, managing postoperative patients in ICUs and on wards, or arranging patient transfers to other facilities.

Discharge planning at ED and hospital levels will require creative coordination in the setting of disasters. Patients displaced by events may find it difficult to return home. Several issues must be considered when discharging such patients: 1) security; 2) physical structure of the patient’s home or extended care facility; 3) status of utilities and food services in that area; 4) accessibility to emergency services (e.g., no telecommunications, EMS overwhelmed) and outpatient healthcare (e.g., portable oxygen, pharmaceuticals, in-home nursing care); and 5) ability

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to return for in-hospital treatments of chronic conditions (e.g., chemotherapy, dialysis).

Although it might be possible for patients to remain in the hospital, this could further limit the admission and treatment capacity of the facility. Patient transfer to less-crowded facili- ties is another option, but one that would require systematic employment of validated protocols guiding “rapid discharge.” In this context, rapid discharge is predicated on a triage method- ology for assessing which admitted patients can be discharged safely from a medical facility to ensure adequate space to treat an incoming surge of casualties.

Only patients without chest complaints who have normal chest radiographs and arterial oxygenation (by paO2 or SpO2) should be considered for ED discharge.75 Missed pulmonary contusions will likely develop relatively slowly, enabling patients to return to the ED provided they have rapid access to an EMS system or good social support and transportation access. Any patient with an abdominal complaint or objective finding should have a surgical consultation and be observed in the hospital. Such patients should not be discharged until BII has been excluded or sufficient time has passed to significantly reduce the possibility of late bowel perforation.75

Patients with only TM rupture may be discharged home with instructions to protect their ear canals from foreign material, including water. Antibiotics are not indicated unless there is established infection with myringitis or otitis follow- ing a delayed presentation. Most perforations will heal spon- taneously, especially those involving less than 80% of the TM surface.82,84

Follow-up Most blast-exposed and blast-injured casualties require some

form of follow-up evaluation for medical concerns, forensic investigations, and the collection of research data. If managed appropriately, BLI mortality and lasting morbidity is not the norm. Follow-up pulmonary examinations of 11 BLI patients admitted to ICUs, who had an average hospital duration of stay of more than 1 month, found that none had respiratory com- plaints, and most had normal chest radiographs and pulmonary function tests 1 year later.228 In a retrospective study examin- ing short- and long-term outcomes of ICU patients following terrorist bombings, only 24% of survivors contacted had some degree of respiratory sequelae 6 months–21 years after injury.196

Care of discharged patients with BII should follow standard surgical practices.75 Patients with TM rupture must be followed for cholesteatoma formation.229

Healthcare Systems

During mass casualty situations, medical care may need modifi- cation, so that the most good can be done for the most peo- ple. Optimal care cannot be provided to all when resources are constrained. The concepts of “essential care” or “minimum acceptable care” may require consideration. While initiatives are underway230 at the time of this writing, there are no standardized definitions for what constitutes these situation-specific levels of care.152 In some circumstances, identifying those who will bene- fit most from “optimal care” may be possible, in which case such individuals would receive high priority for scarce resources.231

Acceptability will likely vary for how each event impacts a given community’s culture of expectations.

Permanent Facilities Hospitals can be directly and adversely affected by explo-

sive blasts, regardless of the cause. Direct explosive damage to healthcare facilities may limit the capacity of casualty receivers to manage those patients who either find their own transporta- tion or are transported by others to surrounding EDs. The most critical problems for operations of healthcare systems are

■ Fire ■ Structural integrity ■ Staff, patient, and visitor injuries ■ Personnel’s ability to access the facility or specific work areas ■ Access to or replenishment of supplies and equipment ■ Functioning utilities and internal and external communica-

tions ■ Adequacy of supervisory and managerial support ■ Transportation of patients into (or out of, if evacuating

patients) and within the facility

Power loss may disrupt lighting, medical equipment, and safety systems. Disruption of water supplies may affect the adequacy of clean drinking water, and water for personal hygiene and infection control. Sewage outflow may also be affected. Widely scattered debris or direct damage to roads may make it difficult for personnel to report for work. Those already on duty at a facil- ity may need to work extended shifts, or additional days, without relief. Supplies may not be replenished and malfunctioning med- ical equipment may not be repaired.

On November 2, 1991 in Belfast, Northern Ireland, bombers targeted the military wing of an orthopedic specialty hospital.31

A device of unknown size was placed in a basement fire exit tunnel near a location where personnel would be watching a major sporting event while off-duty. Two floors above collapsed into the basement room injuring nine people. Two victims died outright; three seriously injured individuals sustained fragment injuries, burns, and smoke inhalation; and four casualties with minor injuries were able to self-extricate.

Only a resident physician, junior surgeon, and anesthesiolo- gist were on duty at the time because no emergency department existed in this particular facility and the detonation occurred during off hours. The resident became the Incident Commander until the local fire department arrived. PPE was not available. Although two wards in the wing were evacuated to other areas of the facility, there were no casualties elsewhere. In this exam- ple of an intentional attack against a hospital, sufficient external resources were available to manage the situation.

A device the size of the one used in Nairobi or Oklahoma City employed against a city’s multistory hospital would likely result in hundreds or thousands of casualties. Many victims, some already inpatients with a wide variety of resource needs, would require evacuation to other area hospitals because the targeted building would likely sustain significant damage and be partially or totally unusable. Hospitals do not typically practice complete evacuations, although the events surrounding the 1994 Northridge earthquake and 2005 Hurricanes Katrina and Rita in the U.S. showed that catastrophic circumstances can make such a drastic and extremely difficult action necessary.232–234

Surge Capacity Surge capacity is a concept that can be intuitively grasped

yet remain difficult to define in specific terms. A broad-scope

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approach to defining a community’s surge capacity must include the following areas: out-of-hospital care (e.g., fire/rescue and EMS), in-hospital care, community and extended care (e.g., free- standing same-day surgery centers, medical clinics, and nurs- ing homes), and medical (e.g., pharmacies, out-patient imag- ing centers) and nonmedical (e.g., electricity, telecommunica- tions, water and sewer) assets supporting healthcare delivery.234

Addressing surge capacity must include each of the aforemen- tioned component areas if a community intends to accurately assess its true overall capacity and to improve its surge response. The U.S. and Israeli military experiences suggest that those pro- viding leadership must understand the art and science of surge capacity to respond successfully in the setting of real-world con- tingencies (Chapter 3). Such issues include risk communica- tion, comprehensive training, creative use of resources, com- mand and control, communications, and effective use of tech- nology.235

Temporary Facilities A variety of temporary facilities might be established by gov-

ernmental and nongovernmental organizations to mitigate the human impact of an overwhelmed healthcare system. In the context of a community’s emergency operations plan, the like- lihood of complete infrastructure disruption by a single non- nuclear explosive event is low. The media could use public service announcements to direct persons in need of medical, sur- gical, psychological, and other services to locations designated by a functioning EOC. Shelter considerations are discussed in Chapter 37.

In disaster situations requiring additional healthcare capac- ity, consideration should also be given to using resources devel- oped for other purposes. An excellent example of this dual-use approach in the United States would be the Modular Emergency Medical System created primarily for a response to biological ter- rorism. If prepared and integrated into a community’s disaster plans prior to an event, the concept provides a framework for expanding community healthcare capacity as required. One or more high-volume reception and triage facilities can be estab- lished directly within affected areas by using the Neighborhood Emergency Help Center concept. This strategy provides initial community healthcare that is more accessible when victims do not have ready access to transportation, roads are impassible or unsecured, EDs are overwhelmed, or there are no post-event functioning healthcare institutions.237 When hospitals are full, the Acute Care Center concept establishes one or more off-site inpatient facilities. These entities are staffed and equipped to manage large volumes of patients with less serious problems, thus allowing hospitals to concentrate on more seriously ill and injured victims.238

Rapid Needs Assessments

The rapid determination of infrastructure dysfunction and initial resource needs is critical to avoiding an ineffective response, and beginning the process of recovery from an explosive event. One or more rapid assessments are necessary to determine the level of response required.239 Aerial surveys of the affected area are probably the best initial method of determining the scope of the problem. If a large region is affected, the U.S. CDC recommends modified cluster sampling as the epidemiological data collection method of choice.240,241 The technique essentially involves iden-

tifying 30 randomly selected clusters of land in the affected area, and then interviewing residents of these areas by using assess- ment teams. Data are then collected and analyzed to estimate rates, which are then extrapolated to total population numbers based on pre-event census information.

On-the-ground needs assessments can also identify victims with injuries and illnesses, whether event related or not. Illnesses may be new or exacerbations of chronic conditions, either from inability to access customary care or exposure to dust, smoke, or other dispersed materials. Healthcare access, in the forms of EMS availability or capabilities of individuals and families to travel to medical facilities, can also be surveyed.

External Response Major disasters disrupt and overwhelm local response capac-

ity to a degree that outside assistance may be required to help mitigate the human impact of the event. Higher levels of gov- ernment may control regional resources. Responses are coor- dinated through an EOC capable of coordinating all necessary resources.

In the United States, federal healthcare assistance to a region may come in the form of a Disaster Medical Assistance Team (DMAT). This is a community-based asset of the National Dis- aster Medical System that has intermittently been under the oper- ational control of the Federal Emergency Management Agency (within the Department of Homeland Security) and the Assistant Secretary for Preparedness and Response (within the Depart- ment of Health and Human Services). DMATs are composed of 50 or more physicians, physician assistants, nurses, pharmacists, respiratory therapists, paramedics, emergency medical techni- cians, and a variety of healthcare, logistical, and administrative personnel. Team members provide medical care during a dis- aster or other local, regional, or state event. They function as rapid-response elements, which are self-sufficient for 72 hours, and supplement local medical care by treating up to 250 patients per day in a fixed or temporary site. Roles and responsibilities of DMATs may include triage, provision of acceptable care in med- ically austere settings, and preparation for evacuation to more appropriate healthcare facilities. DMAT personnel may also be deployed to more distant facilities to assist in receiving large numbers of patients from affected areas. Chapter 9 provides additional information.

Public Information The ultimate goal of any public educational effort is to pre-

vent problems before they occur (Chapter 22). In the United States, the CDC has called for standardization of public health messages issued for a variety of events.242 One purpose of this initiative will be “to receive, manage and disseminate alerts, pro- tocols, procedures and other information for public health work- ers, primary care providers, and public health partners in emer- gency response.”243 Medically related information disseminated to the public and to healthcare personnel should be based on evi- dence where it exists. Messages should focus on immediate and delayed signs and symptoms of injuries incurred following an explosive blast. Representatives of local, regional, or state public health departments and hospital coalitions can facilitate crisis communications via the media, as well as real-time needs assess- ments via ongoing monitoring of the situation. Public health assets can further support the medical community in these scenarios by developing surveillance instruments to enhance

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early identification of TBI and the need for “psychological first aid.”244

RECOMMENDATIONS FOR FURTHER RESEARCH

As with many research questions in public health, it is difficult to measure the results of interventions designed to prevent an out- come. Particularly in the field of disaster medicine, comparisons can usually only be made to similar events that were analyzed in the past. Any research beyond that of observation is hampered by the fact that explosive events are extremely heterogeneous. Exposure time, place, and population are difficult to predict, and the number of exposed individuals is usually relatively small without a valid cohort or control group. For these and other rea- sons, true meta-analyses have not been possible, although some authors have examined multiple individual incidents to deter- mine whether any knowledge can be identified.245–248 There are no prospective, double-blinded, randomized, controlled, clinical trials of blast-injury management in humans.

Natural explosions are rare, but their power ranges from sud- den steam releases that shower debris in the immediate area to volcanic eruptions that explode with forces exceeding those of military-grade nuclear weapons. Accidental explosions related to human activity range from destruction of single houses fol- lowing ignition of concentrated natural gas to massive industrial explosions, which might also include dispersion of hazardous materials. Bombings and other intentional blasts also vary sig- nificantly, ranging from devices rupturing small compressed-gas cylinders to detonations of truckloads of high-order explosives.

The U.S. Bureau of Alcohol, Tobacco, Firearms, and Explo- sives administers the U.S. Bomb Data Center.249 In the 3 years from 2004 to 2006, the most recent period for which data have been compiled, there were 210 accidental explosions killing 39 people and injuring 293. During the same interval, 2,020 intentional bombings occurred, but the injury rate was lower because many of these were directed against property only. For these events, 11 people died and 108 were injured. This U.S. Department of Justice entity does not, however, collect medi- cally relevant data from which to draw more than broad epi- demiological conclusions.52 Data obtained from casualty triage, evaluation, management, and disposition cannot be collected or compared.

Most disaster research should be multidisciplinary and col- laborative, with defined data collection instruments created before events occur.33,49,50,70,71,250

■ Uniform data sets must be created, vetted, and validated for explosive events

■ universally collected during training exercises and real-world responses

■ and shared between agencies and the medical community for analysis and future applications

■ Specific areas of interest would include risk mitigation ■ system preparedness ■ out-of-hospital access, triage, medical care, and evacuation ■ hospital primary triage, resource allocation, and patient

redistribution ■ medical, surgical, and psychological evaluation and manage-

ment ■ and medical and nonmedical infrastructure recovery

Best practices for these have been promulgated by a myr- iad of governmental and nongovernmental organizations. These agencies have codified the knowledge to be gained and applied to the next event; however, little high-quality outcomes research on the response process has been published in open sources.

Response System Preparedness

Security, public safety, protection of critical infrastructure, and preservation of medical capacity must be immediate considera- tions following an explosive event. Therefore, they must also be dominant topics for readiness research. Many organizations have received large amounts of funding for preparedness, mitigation, response, and recovery activities. Decisions on how to spend those funds, however, are often formed from anecdotal reports and personal opinion, not on evidence-based research. Even the concept of all-hazard preparedness (presumably a more efficient method for planning, equipping, and training for a variety of predictable and unpredictable scenarios) has not been rigorously demonstrated to be the best approach for responses to hetero- geneous PICEs. The same could be said about the U.S. National Response Framework and the National Incident Management System (NIMS).

On the other hand, explosive events are a common problem, with which response organizations must contend, whether or not there are evidence-based recommendations for best practices. Standardization, currently through the NIMS structure in the U.S., seems like a good first step toward quality research into all phases of the disaster cycle, assuming that useful data are being collected and appropriately analyzed. Some after-action reports are useful, but they do not constitute research.

One report took a paradigm for approach to disaster response, promulgated by the American Medical Association, and applied it to several recent bombings to determine com- mon findings.150,151,251 Population-based measures of effective- ness must be created for domestic emergency management in all countries, just as they have been for humanitarian responses to disasters and complex emergencies in the developing world.252

Healthcare system surge capacity is another area that deserves increased attention, although it has been a focus for many pro- fessional groups in the last several years.

Hazard Determination

Determining the likelihood of natural or accidental explosions, or detecting the first or additional intentionally planted explosive devices, is a key function of operational risk management. Exces- sive concern for responder safety could delay care for casualties with immediate needs, but overwhelming desire to help victims could lead to responder injury making the overall problem worse. Significant research is being conducted by the U.S. Department of Defense and related agencies to detect improvised explosive devices in military scenarios. Knowledge translation and tech- nology transfer should aid the public safety sector as new tactics, techniques, and procedures are developed.

Depending on the type of explosive event, any one of many active or passive sensing methodologies could be layered to assist in risk determination. Acoustic and seismic; chemical; and elec- tromagnetic, infrared, and visual technologies all exist – but research into their best application, employment tactics, and analysis for decision making is needed. Determining the best

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platforms for these sensors is another question that must be answered. Animals have been used very effectively to detect chemical signatures in the air, and several electronic devices have been designed for similar purposes. Visual and x-ray techniques, either directly by humans or remotely through ground-based robots, are already used by bomb squads and explosive ordnance disposal teams throughout the world. Manned and unmanned aerial systems – from military aircraft to remotely controlled microvehicles – are on the cutting edge of hazard detection.

Personal Protective Equipment

Secondary devices, the possibility of additional explosions, release or threat of hazardous materials release, potential struc- tural collapse or water-vessel sinking, and many other scenarios require protection of responders if they are to implement HACE. PPE for healthcare providers and decontamination of hazardous materials in these situations are addressed in Chapters 13 and 14, respectively. With regard to blast injury, ballistic protection is the most important consideration.

Bomb fragments released after detonation have the potential to cause injury at the greatest distance from the blast site and pen- etrating trauma is the mechanism that kills or injures the major- ity of victims in the absence of structural collapse.50,75,253,254

Intervening barriers protect against secondary blast injury but not PBI.75,81 Helmets and body armor are crucial in preventing penetrating injury to critical organs, but the latter can increase coupling of the blast wave to the body surface and may magnify its translation into internal stress waves.82,255–257 Some research and reviews on improved armor designs have been published in the medical literature but more work would be beneficial.258–260

Research into hearing protection that remains functional in the out-of-hospital environment is also needed.

Clinical Care

Many more questions than evidence-based answers exist in the research agenda for blast injuries. Triage, for instance, requires substantial additional scientific investigation.261 Even the abil- ity to effectively conduct triage in situations with significant ongoing threats has been questioned.262 Several authors have retrospectively applied mass casualty triage systems to patients in existing databases in an attempt to answer some of these questions.149,153,157,158,263 No significant prospective research has been published, however.

From the field, what is the best destination for casualties in each of the four most common triage categories? Should those with minimal injuries be primarily directed or sent to hospitals out of the affected region? In rural settings, should victims be taken to a closer hospital for stabilization or evacuated over longer distances to a regional trauma center?

In the field or in the hospital, how much medical evaluation is required for a blast-exposed individual without significant external injury? Does categorization into mild, moderate, and severe BLI based on imaging and PFR assist in subsequent clin- ical decision making? Do interventions based on any catego- rization method have a significant impact on outcome? Design- ing research investigations to answer these questions is difficult given the complex environments involving different overpres- sures, body positions relative to the blast front, intervening bar- riers and armor, and quaternary effects on fixed structures and

moving vehicles. Specific injury types and their severities occur over a wide range of blast overpressures.

Do seemingly minor head injuries have long-term conse- quences and therefore require early detection? No specific risk factors for BLI sequelae have been found other than those related to ARDS. The brain may be different, however. Further research on TBI is needed, but the degrees to which ultrastruc- tural and functional changes contribute to the problem are still largely unknown. If inflammatory and neurohumoral mecha- nisms are pathophysiologically important, can they be modu- lated to improve outcomes?

Does specific early management of nonlife-threatening injuries change long-term outcome? In military theaters of oper- ation, there is a significant effort being made to identify blast- exposed persons at risk for TBI. Unlike most civilian populations, military populations are expected to be at risk for blast trauma. Therefore, pre- and postexposure MACE scores can be obtained and compared after any event.

How do primary blast injuries obscure the management of other trauma during and after initial resuscitation? Massive hemoptysis can certainly complicate airway management. Ten- sion pneumothoraces can often be bilateral and involve bron- chopleural fistulae. Systemic air embolism is difficult to diagnose and treat during initial trauma resuscitation.

Should “standard” resuscitation measures be adjusted for blast-exposed casualties? Is it beneficial to place a blast victim in a different body position (rather than supine)? Can left lateral, left semilateral decubitus, or prone position improve oxygena- tion or decrease the risk of systemic air embolism? Does delay of intubation and PPV until absolutely necessary improve or worsen outcomes? Higher airway pressure may be required to oxygenate, but excessive airway pressure may increase risk of pneumothorax and systemic air embolism. Shock must be avoided or reversed and inadequate fluid resuscitation may perpetuate lower pul- monary venous pressures, thus increasing the risk of systemic air embolism. Is there any difference between standard 20-mL/kg crystalloid fluid boluses compared with smaller, more frequent aliquots of fluid with regard to improving perfusion without causing secondary lung or brain injury? Is there a best fluid type?

Potential complications related to standard operative and critical care also deserve additional research. What are the risks of tension pneumothorax and tension pneumoperitoneum? Are prophylactic chest tubes necessary and safe for PPV, inhala- tional anesthetic, or air transport as advocated by some expe- rienced authorities? Can ventilator-associated complications be prevented by assessing specific risk factors or taking prophylac- tic measures? Could early independent lung ventilation decrease complications and improve outcome?

Longitudinal Studies

Blast-injured casualties should be followed long term for the emergence of medical and neuropsychiatric sequelae. In addi- tion, researchers should examine the impact of blast exposure on the lives of victims in general as well as their families and society as a whole. Most of the recent longitudinal studies on primary and secondary blast injuries have evaluated eye and ear trauma.59,60,264–273 Two studies have suggested that late sequelae from BLI are unusual.196,228 No longitudinal studies of BII could be found in the literature.

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Although many longitudinal mental health studies have examined survivors from the 1995 Oklahoma City bombing, research into the neuropsychiatric ramifications of sudden and unexpected trauma following explosions has just begun receiving significant attention and funding. In 2008, the U.S. Department of Defense announced a 300 million dollar effort to fund research in the epidemiology, clinical care, and long-term effects of TBI and posttraumatic stress disorder. The U.S. Congress has also appropriated nearly as much to study battlefield injuries. Both of these efforts should substantially increase the world’s ability to care for blast victims.

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