D

Vol.:(0123456789)1 3

Journal of Clinical Monitoring and Computing (2022) 36:215–220 https://doi.org/10.1007/s10877-020-00639-z

ORIGINAL RESEARCH

Comparison of two forced air warming systems for prevention of intraoperative hypothermia in carcinoma colon patients: a prospective randomized study

Abhity Gulia1 · Nishkarsh Gupta4  · Vinod Kumar1  · Sandeep Bhoriwal2 · Rajeev Kumar Malhotra3  · Sachidanand Jee Bharti1  · Rakesh Garg1  · Seema Mishra1  · Sushma Bhatnagar1

Received: 25 August 2020 / Accepted: 17 December 2020 / Published online: 16 January 2021 © The Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature 2021

Abstract Hypothermia is common occurrence in patients undergoing colonic surgeries. We hypothesized that the underbody forced air warming blankets will be better than conventional over-body forced air warming blankets for prevention of hypothermia during laparoscopic colon surgeries. After ethics approval, sixty patients undergoing elective laparoscopic colon surgeries were randomly divided into two groups to receive warming by underbody forced air warming blanket (n = 30) or over-body forced air warming blanket (n = 30). In the operating room, epidural catheter was inserted and thereafter warming was started with the forced air warmer with temperature set at 44 °C. Intraoperatively core temperature (using nasopharyngeal probe), vitals, incidence of postoperative shivering and time to reach Aldrete Score of 10 in the postoperative period were recorded. The core temperature was higher with an underbody blanket at 60 min (36.1 ± 0.5 °C vs. 35.7 ± 0.5 °C, P = 0.005), 90 min (35.9 ± 0.5 °C vs. 35.6 ± 0.5 °C, P = 0.009), 120 min (35.9 ± 0.5 °C vs. 35.5 ± 0.4 °C, P = 0.007), and 150 min (35.9 ± 0.5 °C vs. 35.6 ± 0.4 °C, P = 0.011). In the post anesthesia care unit, the time to reach an Aldrete score of 10 was also less in the underbody blanket group (14.3 ± 2.5 min vs. 16.8 ± 3.6 min) (P = 0.003). However, there were no clinically meaningful dif- ferences in any outcome. Underbody and over-body blankets were comparably effective in preventing hypothermia in patients undergoing laparoscopic colorectal surgery under general anaesthesia. Trial registration CTRI (2019/06/019,576). Date of Registration: June 2019, Prospectively registered.

Keywords Hypothermia · Forced air warming · Colorectal surgery · Laparoscopy

1 Introduction

Hypothermia is common in patients undergoing long-dura- tion surgeries under general anaesthesia (GA). There is a rapid decline in core temperature during the initial one hour

after induction of GA due to the redistribution of heat from the central compartment towards the peripheral thermal compartment [1]. In major abdominal surgeries like carci- noma colon, a significant portion of the patient’s surface area is exposed to cold ambient environment for a prolonged duration which increases the risk of hypothermia. Mild intraoperative hypothermia increases wound infection [2], bleeding [3, 4], cardiac complications [5], and may prolong recovery [6].

The degree of intraoperative hypothermia depends on the pre-surgery thermal status of the patient [7], the patients’ age and body surface area [8], the temperature of the operating theatre [9] and the surgical incision size [10].

Various methods have been used to prevent intraoperative hypothermia like pre-induction warming of patients [11], water mattresses, [12] circulating-water garments, [13, 14] forced air warming devices, [11] and infusion of warm fluids [11]. Forced air warming is the most effective and safest

* Nishkarsh Gupta [email protected]

1 Department of Onco-Anesthesia and Palliative Medicine, Dr.B.R. Ambedkar, IRCH, All India Institute of Medical Sciences, New Delhi, India

2 Department of Surgical Oncology, Dr.B.R. Ambedkar, IRCH, All India Institute of Medical Sciences, New Delhi, India

3 Delhi Cancer Registry, Dr.B.R. Ambedkar, IRCH, All India Institute of Medical Sciences, New Delhi, India

4 Department of Onco-Anaesthesia and Palliative Medicine, Dr. B.R. Ambedkar, IRCH, All India Institute of Medical Sciences, Room No 139, First floor, New Delhi, India

216 Journal of Clinical Monitoring and Computing (2022) 36:215–220

1 3

worming approach that is widely used during surgery [11, 15].

Commonly used over-body forced air warming blankets may be of limited usefulness in abdominal surgeries like colectomy because a large part of the anterior abdominal wall needs to be exposed for surgery and cannot be covered with the blanket.

The underbody forced air warming blankets may be better than conventional over-body forced air warming blankets in preventing intraoperative hypothermia because they cover the entire body irrespective of the type of surgical exposure and provide continuous heat in patients. But the literature on the effectiveness of underbody blankets in preventing hypothermia in a homogenous population of patients is lim- ited. We decided to compare the effectiveness of over-body and underbody blankets for the prevention of intraoperative hypothermia in patients undergoing laparoscopic colectomy.

We hypothesized that the underbody forced air warming blankets will be better than conventional over-body forced air warming blankets for prevention of hypothermia during laparoscopic colon surgeries.

The primary outcome was intraoperative mean difference in temperature in the two groups at the end of surgery. The secondary outcomes included intraoperative hemodynamic parameters, intraoperatively amount of fluids used, postop- erative recovery as assessed by Aldrete score and any inci- dence of shivering in the two groups.

2 Methods

After approval of the ethics committee and prospective CTRI (2019/06/019576) registration, this randomized con- trolled study was done in 60 adults (18–65 years), American Society of Anesthesiologists (ASA) Grade I and II patients of either sex posted for elective laparoscopic colon surger- ies in a tertiary care centre. The patients with uncontrolled hypertension, coronary artery disease, morbid obesity (BMI > 40 kg/m2), preoperative body temperature > 37.5 °C and those with surgery expected to last less than 2 h were excluded.

After a detailed pre-anaesthetic checkup and informed consent, the patient was randomly allocated into two groups (n = 30) by simple randomization using computer-generated random numbers. The allocation of participants was con- cealed using sealed opaque envelopes which were opened by the anesthetist on the morning of surgery just prior to shifting of the patient to the operating thetare (OT). In the OT, room temperature (set at 22-degree Celsius), patient’s core body temperature, ECG, non-invasive mean blood pres- sure (MBP), heart rate (HR), and end-tidal carbon dioxide (EtCO2) were recorded. In the OT, the patients received

forced air warming with underbody blanket (n = 30) or over- body blanket (n = 30) as per group allocation.

The standard monitors were attached as soon as the patient was shifted to the operating room. In all patients, a lumbar epidural catheter was inserted under aseptic precau- tions at the L1-L2 level in the left lateral position before the induction of anaesthesia. The warming was initiated with the equator forced air warming system (EQUATOR® level I Convective Warming Device (Smith Medical ASD, MN, USA), immediately after the epidural insertion with tem- perature of the warmer set at 44 °C. The forced air warming was switched off if the patient’s body temperature increased to 37.5 degrees Celsius. Intraoperatively, the core body tem- perature, MBP, HR, and EtCO2 were recorded every 2 min for 10 min and every 5 min thereafter. Plasmalyte infusion was given to all patients at the rate of 4–6 ml/kg/h through the fluid warmer (3 M™ Ranger™ Fluid Warming System (3 M healthcare, MN, USA) set at 41 °C.

General anaesthesia was administered to all patients using fentanyl 2 µg/kg, propofol 2–2.5 mg/kg, and neuromuscu- lar blockade was achieved with rocuronium 0.6–0.8 mg/kg. Anaesthesia was maintained using desflurane (5–6%) in O2 and air. All patients were given intravenous paracetamol 1 gm for analgesia immediately after the start of surgery. The core body temperature was recorded using an adult nasopharyngeal probe (Drager Medical systems, Inc., 3135 Quarry Road, Telford, PA, USA) inserted into the more pat- ent nostril to a pre-determined length (distance from tragus to nares) immediately after anaesthesia induction. Baseline temperature was taken as the body temperature of the patient immediately after the induction of anaesthesia in the opera- tion theatre. The patients received repeated doses of fentanyl of 1 µg/kg depending upon the hemodynamic parameters intraoperatively.

Following the operation, the patient’s trachea was extu- bated and shifted to the recovery room where the time to reach Aldrete Score 10 was recorded by a blinded observer. A decrease in HR to less than 20% from the baseline value or an absolute HR < 55 beats per minute was defined as bradycardia and managed with 0.6 mg IV atropine. A decrease in the BP of 20% from baseline or an absolute MBP < 60 mmHg was considered as hypotension. It was managed by a 2 ml/kg bolus of IV Plasmalyte, and injec- tion Mephentermine 6 mg IV if needed. The contact area of the skin with warmer was assessed for any associated com- plications (e.g. erythema, oedema, bullous swelling, etc.). Any other side-effects like shivering and sweating were also noted.

2.1 Statistical analysis

The data were analyzed by the SPSS-16 statistical soft- ware (SPSS Inc. Chicago, USA). A linear mixed model

217Journal of Clinical Monitoring and Computing (2022) 36:215–220

1 3

was applied to compare the mean temperature between and within the group. Akaike information criterion (AIC) was applied to choose the best covariance structure. For tem- perature, the first-order autoregressive covariance structure gave the minimum AIC value. First, the interaction between the time points and groups was investigated, a significant interaction revealed a different pattern of the variable between the groups across the time points, in such a situa- tion comparison between the groups was determined at each time point and p-value adjusted for multiple comparisons. Assuming a 0.5 average correlation between the time point values, p-value 0.012 (0.05/4 was considered as significant instead of 0.05 for the linear mixed model for calculating the p-value at 30 min interval during the surgery). For the remaining analysis p-value, less than 0.05 was considered as significant. We used unpaired student t-test to compare the mean values for continuous variables and Fisher’s exact test/Chi-square test for categorical variables.

To detect a difference of 0.5 °C (SD of 0.6) at the end of the surgery between the underbody and over-body blanket

with 90% power and 5% level of significance, a sample size of 30 subjects in each group was required [16].

3 Results

A total of seventy patients undergoing colectomy were assessed for eligibility and of these 60 were recruited for the trial (Fig. 1). The patient’s demographics including age, sex, weight, and height were comparable between the two groups. (Table 1).

Baseline temperature was comparable in the two groups (36.0 ± 0.5 °C underbody vs. 36.0 ± 0.4 °C over-body) (p = 0.817) at baseline. After induction of anesthesia, the core temperature decreased in all the patients. The decrease in temperature was less in patients of under- body as compared to over-body at 60 min (36.1 ± 0.5 °C vs. 35.7 ± 0.5 °C, P = 0.005), 90 min (35.9 °C ± 0.5 vs. 35.6 ± 0.5  °C, P = 0.009), 120  min (35.9 ± 0.5  °C vs.

Patients scheduled for Carcinoma Colon surgeries, 18-65 years Assessed for eligibility (n=70)

Excluded (n=10)

participate (n=3)

Patients in Under-body Forced air warming group analysed (n=30)

Lost to follow-up (n=0)

Allocated to Under-body Forced air warming group (n=30)

Lost to follow-up (n=0)

Allocated to Over-body Forced air warming group (n=30)

Patients in Over-body Forced air warming group analysed (n=30)

Allocation

Analysis

Follow-Up

Randomized (n=60)

Enrollment

Fig. 1 Consort flowchart

218 Journal of Clinical Monitoring and Computing (2022) 36:215–220

1 3

35.5 ± 0.4 °C, P = 0.007), and 150 min (35.9 ± 0.5 °C vs. 35.6 ± 0.4 °C, P = 0.011) (Table 1; Fig. 2).

There was no significant difference in mean MBP, EtCO2, and HR values between the two groups during the surgery. The intraoperative variables like duration of surgery, amount of fluid administration, and urine out- put were also comparable. The time to reach the Aldrete score of 10 was significantly less in underbody forced air warming group (p = 0.003). (Table 1) Shivering was noted in 4 patients in the ove- body forced air warming group whereas only 1 patient had shivering in the underbody

forced air warming group. No other complications with seen in any of our patients.

4 Discussion

In our study we have compared two types of forced air warming blankets for preventing hypothermia and found that both the blankets were effective in preventing hypothermia at various time points in patients undergoing laparoscopic colon surgeries under general anaesthesia. Hypothermia is a common occurrence under general anaesthesia and forced

Table 1 Demographics, preoperative variables and intraoperative variable in the two groups

Demographic Underbody forced air warm- ing

Over-body forced air warm- ing

P value Absolute standardized dif- ference

Age 52 ± 13 51 ± 12 0.642 0.111 Weight 62 ± 9 64 ± 9 0.299 0.270 Height 164 ± 8 163 ± 7 0.670 0.111 Sex (M:F) 15:15 16:14 0.796 0.067 Preop CT (NO:YES) 27:3 19:11 0.015 0.664 Preop RT (NO:YES) 26:4 19:11 0.037 0.560 Comorbidity (NO:YES) 18:12 15:15 0.436 0.202 ASA (I:II) 18:12 15:15 0.436 0.202 Duration of anesthesia (min) 227 ± 32 214 ± 31 0.106 0.424 Duration of surgery (min) 183 ± 30 171 ± 26 0.089 0.447 Total IV fluid administered (ml) 1528 ± 348 1593 ± 296 0.439 0.201 Urine output (ml) 338 ± 108 324 ± 96 0.599 0.136 Time to reach Aldrete score 10 (min) 14 ± 2 17 ± 4 0.003 0.949

Fig. 2 Comparison of mean of temperature between the groups

219Journal of Clinical Monitoring and Computing (2022) 36:215–220

1 3

air warming systems have been used since long time to effec- tively prevent it. With the improvement in technology newer underbody forced air warming blankets have been made available. The efficacy of underbody blankets in preventing hypothermia has been tested in a few studies and has found to be better than control (no forced air warming) in prevent- ing hypothermia [17, 18].

Insler et  al. [19] reported that underbody forced air warming system, when used in addition to insulation and fluid warming, was better thansssss fluid warming and passive insulation alone for hypothermia management (36.3 °C ± 0.6 °C vs. 35.7 °C ± 0.5 °C respectively) in the pre-bypass phase. However, there are a few prospective stud- ies that have compared underbody forced air warming blan- kets with over-body forced air warming blankets. Miyazaki et al. [16] retrospectively studied and compared underbody forced air warming with over-body forced air warming for laparoscopic nephrectomy and found that underbody forced air warming resulted in a significantly higher temperature at the end of surgery. This may be due to a continuous sup- ply of forced air warming by underbody blanket whereas an over-body blanket may not be able to cover a large area involving the surgical site. The effect of forced air warming systems depends upon the surface area of the patients’ body covered by the warming blanket. The difference between two blankets becomes more evident in patients undergoing major abdominal surgery where the surface exposed is much more than a peripheral surgery due to the need for surgical procedure. Moreover, in laparoscopic abdominal surgeries, almost the whole abdomen will be exposed leaving a small area for over-body forced air warming to act.

Alparslan et al. [20] studied open lower abdominal surgi- cal patients and found no difference in average intraopera- tive temperature between underbody forced air warming and over-body forced air warming system (P = 0.268). So, their results suggested a good effect on hypothermia prevention with underbody like our findings but had contrary results in terms of stating the superiority of underbody blanket. This could be attributed to the shorter duration of gynecological surgeries (around 2 h) unlike much longer duration colorec- tal surgeries (180 min) in our study.

An increase in body temperature by underbody blankets may lead to additional thermal stress on the body and acti- vate the sympathetic system. This may lead to hypertension and tachycardia. However, in our study, the intraoperative mean blood pressures were comparable between the two groups. This suggests that there was no additional thermal stress by underbody forced air warming despite a better warming potential. Similar results were reported byAl- parslan et al. [20].

Hypothermia is known to cause delayed recovery [6]. Miyazaki et al. [16] reported a significantly shorter time (p < 0.05) to extubation in underbody forced air

warming(16 ± 7 min) when compared to over-body forced air warming (29 ± 22 min). However, Alparslan et al. reported similar Aldrete scores for assessing recovery times in both the groups [20]. In our study, underbody forced air warming blanket resulted in lesser time (3 min, P = 0.003) to reach the Aldrete score of 10 that was clinically insignificant. It also resulted in lesser incidence of shivering which further reiterates the effectiveness of the in preventing hypothermia.

With the present findings of our study, we suggest that underbody forced air warming is equally effective for the prevention of hypothermia in patients undergoing major abdominal laparoscopic surgeries.

The strengths of the present study are that it was con- ducted in a homogenous group of study subjects with the duration of surgery for more than two hours. There are a few limitations. Firstly, our study is a single-centre study and results may not be generalizable in all settings. Our patients underwent laparoscopic colorectal surgery and the effect of the two blankets may vary with other surgeries. The differ- ence in the effect may not be as apparent in minor surgeries involving limited exposure. Also, this study was done in a small number of patients and a study with a larger sample size is needed to further validate the effect. The assumed dif- ference for sample size calculation at 90% power could not be demonstrated in our study. The maximum difference 0.37 degree at 60 min which is less than 0.5 degree. However, there is not much difference in the effect size at 60 min. The effect size (Cohen’s) was considered 0.83 for determining the sample size and 0.79 at 60 min in our study.

5 Conclusion

Underbody and over-body blankets were comparably effec- tive in maintaining core temperature in patients undergoing laparoscopic colorectal surgery under general anaesthesia.

Author contributions AG contributed to literature search, data acquisi- tion, manuscript preparation and editing. NG contributed to concepts, design, literature search, manuscript editing and review. VK contrib- uted to concept, manuscript editing and review. SB contributed to manuscript editing and review. RKM contributed to data analysis and statistics. RG, SJB, SM and SB contributed to manuscript editing and review. All authors approved the final version of the manuscript.

Funding No external funding of any sort is involved.

Data availability Data is available.

Compliance with ethical standards

Conflict of interest No conflict of interest is involved in the present study.

220 Journal of Clinical Monitoring and Computing (2022) 36:215–220

1 3

Ethics approval Institutional ethical approval was obtained before start of the study (IEC-474/09.2018).

Informed consent Written informed consent was obtained from all the patients prior to their inclusion in the study. We give our full free and voluntary consent to the Journal for the publication and copyright of the article.

References

1. Matsukawa T, Sessler DI, Sessler AM, Schroeder M, Ozaki M, Kurz A, et al. Heat flow and distribution during induction of gen- eral anesthesia. Anesthesiology. 1995;82(3):662–73.

2. Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hos- pitalization. Study of Wound Infection and Temperature Group. N Engl J Med. 1996;334(19):1209–15.

3. Winkler M, Akça O, Birkenberg B, Hetz H, Scheck T, Arkiliç CF, et al. Aggressive warming reduces blood loss during hip arthro- plasty. Anesth Analg. 2000;91(4):978–84.

4. Schmied H, Kurz A, Sessler DI, Kozek S, Reiter A. Mild hypo- thermia increases blood loss and transfusion requirements during total hip arthroplasty. Lancet Lond Engl. 1996;347(8997):289–92.

5. Frank SM, Fleisher LA, Breslow MJ, Higgins MS, Olson KF, Kelly S, et al. Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events. A randomized clinical trial. JAMA. 1997;277(14):1127–34.

6. Lenhardt R, Marker E, Goll V, Tschernich H, Kurz A, Sessler DI, et al. Mild intraoperative hypothermia prolongs postanesthetic recovery. Anesthesiology. 1997;87(6):1318–23.

7. Just B, Trévien V, Delva E, Lienhart A. Prevention of intraopera- tive hypothermia by preoperative skin-surface warming. Anesthe- siology. 1993;79(2):214–8.

8. Frank SM, Beattie C, Christopherson R, Norris EJ, Rock P, Parker S, et al. Epidural versus general anesthesia, ambient operating room temperature, and patient age as predictors of inadvertent hypothermia. Anesthesiology. 1992;77(2):252–7.

9. Pei L, Huang Y, Xu Y, Zheng Y, Sang X, Zhou X, et al. Effects of ambient temperature and forced-air warming on intraoperative core temperature: a factorial randomized trial. Anesthesiology. 2018;128(5):903–11.

10. Matika R, Ibrahim M, Patwardhan A. The impor- tance of body temperature: an anesthesiologist’s perspective. Temperature 2016;4(1):9–12.

11. Moola S, Lockwood C. Effectiveness of strategies for the manage- ment and/or prevention of hypothermia within the adult periopera- tive environment. Int J Evid Healthc. 2011;9(4):337–45.

12. Hynson JM, Sessler DI. Intraoperative warming therapies: a com- parison of three devices. J Clin Anesth. 1992;4(3):194–9.

13. Taguchi A, Ratnaraj J, Kabon B, Sharma N, Lenhardt R, Sessler DI, et al. Effects of a circulating-water garment and forced-air warming on body heat content and core temperature. Anesthesiol- ogy. 2004;100(5):1058–64.

14. Grocott HP, Mathew JP, Carver EH, Phillips-Bute B, Landolfo KP, Newman MF, et al. A randomized controlled trial of the Arctic Sun Temperature Management System versus conventional meth- ods for preventing hypothermia during off-pump cardiac surgery. Anesth Analg. 2004;98(2):298–302.

15. Madrid E, Urrútia G, Roqué i Figuls M, Pardo-Hernandez H, Campos JM, Paniagua P, Maestre L, Alonso-Coello P. Active body surface warming systems for preventing complications caused by inadvertent perioperative hypothermia in adults. Cochrane Data- base Syst Rev. 2016;4:009016.

16. Miyazaki R, Hayamizu K, Hoka S. Underbody forced-air warmer blanket is superior to overbody blanket in preventing hypothermia during laparoscopic donor nephrectomy. Middle East J Anesthe- siol. 2017;24:43–8.

17. Teodorczyk JE, Heijmans JH, van Mook WNKA, Bergmans DCJJ, Roekaerts PMHJ. Effectiveness of an underbody forced warm-air blanket during coronary artery bypass surgery in the prevention of postoperative hypothermia: a prospective controlled randomized clinical trial. Open J Anesthesiol. 2012;02:65–9.

18. Pu Y, Cen G, Sun J, Gong J, Zhang Y, Zhang M, et al. Warm- ing with an underbody warming system reduces intraoperative hypothermia in patients undergoing laparoscopic gastrointes- tinal surgery: a randomized controlled study. Int J Nurs Stud. 2014;51:181–9.

19. Insler SR, Bakri MH, Nageeb F, Mascha E, Mihaljevic T, Sessler DI. An evaluation of a full-access underbody forced-air warm- ing system during near-normothermic, on-pump cardiac surgery. Anesth Analg. 2008;106(3):746–50.

20. Alparslan V, Kus A, Hosten T, Ertargin M, Ozdamar D, Toker K, et  al. Comparison of forced-air warming systems in pre- vention of intraoperative hypothermia. J Clin Monit Comput. 2018;32(2):343–9.

Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.