Stats report

Running head: STATISTICAL ANALYSIS PROJECT ON POST-OPERATIVE N/V 1

Statistical Analysis Project on Post-Operative Nausea and Vomiting

Brenda Venvertloh

Olivet Nazarene University

Statistics

BSN 198/MATH 120

Dr. Dan Green

September 15, 2015 Certification of Authorship: I certify that I am the author of this paper and that any assistance I

received in its preparation is fully acknowledged and disclosed in the paper. I have also cited

any sources from which I used data, ideas, or words, either quoted directly or paraphrased. I also

certify that this paper was prepared by me specifically for the purpose of this assignment.

Your Signature: Brenda Venvertloh RN, CAPA

STATISTICAL ANALYSIS PROJECT ON POST-OPERATIVE N/V 2

Abstract

The purpose of this case-controlled observational study is to determine if the proportion of men

or women experience post-operative nausea and vomiting after general anesthesia more often

than the opposite gender. Post-operative nausea and vomiting proves to be very debilitating for

many patients. The population of this study is all outpatient surgical patients who receive general

anesthesia. Data was obtained through random samples of patients that received general

anesthesia for outpatient procedures at a hospital based surgical center. Permission was granted

by the manager of the surgical department to use the data for statistical purposes for this

assignment. No personal or demographic information was used to protect the confidentiality of

the patients. This paper will discuss statistical methods used to analyze the data collected for this

project. Results will be revealed through graphs and statcrunch computations. My hypothesis is

that women experience post-operative nausea/vomiting at a higher proportion than men. This

hypothesis is based on observations and experience as a nurse with years of experience in

perianesthesia nursing.

STATISTICAL ANALYSIS PROJECT ON POST-OPERATIVE N/V 3

Statistical Analysis Project on Post-operative Nausea/Vomiting

Introduction

Post-operative nausea and vomiting after general anesthesia proves to be very debilitating

for many patients. In fact, according to the American Society of Perianesthesia nurses, post-

operative nausea and vomiting is the most common complication after general anesthesia that

affects one third of all surgical patients each year (McLaughlin, 2010). Due to the fact that this

complication may lead to unanticipated or prolonged hospital stays, it is important to identify

high risk patients in order to be pro-active in prevention and treatment of post-operative nausea

and vomiting. This statistical analysis project focuses on the topic of post-operative nausea and

vomiting, with the specific question being, which gender is affected by post-operative nausea

and vomiting after general anesthesia at a higher proportion, men or women? I hypothesize that

women experience post-operative nausea and vomiting after general anesthesia at a higher

proportion than men.

The information gained from this project could be supportive of evidence based practice

recommendations in regards to post-operative nausea and vomiting. “It remains one of the most

predictable indicators of prolonged postoperative stays, unplanned admissions and delayed return

to activities of daily living and employment”(Sites et al., 2014, p. 12-13). Negative outcomes

can certainly occur due to post-operative nausea and vomiting as well. Complications from post-

operative nausea and vomiting cost health care providers and insurers millions of dollars per year

(Sites et al., 2014). Post-operative nausea and vomiting may also have a huge impact on patient

satisfaction scores. Patients that are affected by post-operative nausea and vomiting are not as

likely to remember the good aspects of their care. The purpose of this project is to identify

which gender is affected at a higher proportion so nurses may identify and advocate for

STATISTICAL ANALYSIS PROJECT ON POST-OPERATIVE N/V 4

preventative measures to be taken in order to lower the post-operative nausea and vomiting

statistics.

METHODS

Participants

The population of this statistical analysis project is all patients who have outpatient

surgery with general anesthesia. The sample was a subset of 50 female individuals and 50 male

individuals who had outpatient surgery with general anesthesia at a hospital based surgery center.

The samples were selected randomly out of all outpatients who had general anesthesia in a two

week period at a hospital based surgery center. The exclusion criteria were patients that were to

be admitted after surgery and patients who only had local anesthesia.

Materials

A follow-up phone call form was used to collect the data for this project. Outpatients are

notified by the surgery center nurses the day after surgery. Patients are asked several questions

regarding their experience with surgery, their care at the surgery center, and any complications

they may be experiencing. Two questions on the form address post-operative nausea and

vomiting. The only question that was used in the data collection for this project was, “Did you

experience any nausea or vomiting after surgery?”

Procedure

First of all, I determined the objective to conduct my statistical analysis project. I have

worked in perianesthesia nursing for a number of years and have observed that it seems women

tend to experience post-op nausea and vomiting more frequently than men. I thought it would be

interesting to analyze whether this is true in a study of patients in the department that I work in.

Then, I determined this would be a case-control study, meaning that this was retrospective in

STATISTICAL ANALYSIS PROJECT ON POST-OPERATIVE N/V 5

nature. I had to look at data that had already been collected, the follow-up phone call form. The

only thing required of the subjects in this study was to respond and answer the question

regarding post-operative nausea and vomiting when the follow-up phone call was made. Since it

would be impossible for me to conduct research on the entire population, I decided to collect a

random sample of data from 50 men and 50 women to analyze. As I have learned in this course,

larger sample sizes show more congruency in relation to the normal population. To obtain the

random sample, I collected all follow-up call sheets from a 2 week period and divided them into

a group of women forms and a group of men forms. I had another nurse randomly select 50 from

each group, essentially like “drawing out of a hat”. Each form had a random chance of being

chosen. Next, I tallied how many positive responses for post-operative nausea and vomiting for

each gender. The data collected for my statistical analysis project included qualitative variables

since gender is a qualitative variable. I also calculated the data into percentages, meaning that

the statistical methods used to perform inference had to be appropriate to population proportion,

not µ. (Sullivan & Woodbury, 2015).

RESULTS

At face value, the results from my sample populations showed that women experience

post-operative nausea and vomiting at a higher proportion than men. 16 out of 50 women

reported nausea/vomiting after general anesthesia, which computes to 32%. Only 6 men out of

50 reported nausea/vomiting after general anesthesia, which computes to 12%. Statcrunch was

used to construct the following graphical displays. A bar graph was used to show the

comparison of positive responses of nausea/vomiting for each gender. Pie charts were also used

as a visual to compare the percentages of post-operative nausea/vomiting for each gender.

STATISTICAL ANALYSIS PROJECT ON POST-OPERATIVE N/V 6

GRAPHICAL DISPLAYS – Pie Charts

STATISTICAL ANALYSIS PROJECT ON POST-OPERATIVE N/V 7

GRAPHICAL DISPLAY - Bar Graph

Positive Responses to

Post-Operative N/V

In order to apply the results from my sample to the entire population, inferential statistical

analysis had to be done. Using statcrunch, I have determined a 95% confidence interval for each

gender, and performed hypothesis testing to determine the difference between two population

proportions at the level of significance of alpha = 0.01. Requirements for constructing the

inferential statistics of confidence levels and testing the hypothesis are as follows:

1. The samples were obtained using simple random sampling.

2. n1p1 (1-p1) ≥10 and n2p2 (1-p2) ≥10,sample and proportion 1 being women, sample

and proportion 2 being men. Computations are as follows:

women – 50(.32)(1-.32)=10.88 which is greater than 10

STATISTICAL ANALYSIS PROJECT ON POST-OPERATIVE N/V 8

men- 50(.12)(1-.12)=5.28 which is not greater than 10

3. n1≤0.05N1, meaning that the sample size of 50 women who had outpatient surgery with

general anesthesia is less than the entire population of women who had outpatient surgery

with general anesthesia. This proves the same for men using the same formula,

n2≤0.05N2 (Sullivan & Woodbury, 2015).

Using statcrunch, the following confidence intervals were computed for each gender.

95% confidence interval results: N2, MEN p : Proportion of successes

Method: Standard-Wald Proportion Count Total Sample Prop. Std. Err. L. Limit U. Limit

p 6 50 0.12 0.045956501 0.029926913 0.21007309

95% confidence interval results: N1, WOMEN p : Proportion of successes Method: Standard-Wald Proportion Count Total Sample Prop. Std. Err. L. Limit U. Limit

p 16 50 0.32 0.06596969 0.19070178 0.44929822

Hypothesis test results: Women p1 and Men p2

p1 : proportion of successes for population 1 p2 : proportion of successes for population 2 p1 - p2 : Difference in proportions

H0 : p1 - p2 = 0 HA : p1 - p2 > 0 Difference Count1 Total1 Count2 Total2 Sample Diff. Std. Err. Z-Stat P-value

p1 - p2 16 50 6 50 0.2 0.082849261 2.4140227 0.0079

This means that we are 95% confident that the population proportion of men who

experience nausea and vomiting following outpatient surgery with general anesthesia falls

between .03 and .21. Also, we are 95% confident that the population proportion of women

who experience nausea and vomiting following outpatient surgery with general anesthesia falls

STATISTICAL ANALYSIS PROJECT ON POST-OPERATIVE N/V 9

between .19 and .45. Since the P-value of 0.0079 is less than the level of significance at the

alpha level of 0.01, the null hypothesis would be rejected. This means that there is sufficient

evidence that the population proportion of women who have outpatient surgery with general

anesthesia experience post-operative nausea and vomiting at a higher proportion than men

(Sullivan & Woodbury, 2015).

According to the results of this study, my hypothesis was correct. Minimal data was

obtained due to time constraints and to protect the confidentiality of the sample patients. As

mentioned earlier, the men’s sample did not meet one of the requirements for the inferential

statistical testing. Also, there are many lurking variables that could skew the results of this

study. Examples of lurking variables could be the general health of the patient, any previous

history of post-op nausea/vomiting, history of motion sickness, the experience of the nurse

caring for the patient post-operatively, under reporting of post-operative nausea/vomiting

during the follow-up phone call, and the anesthesia provider’s aggressiveness in prevention of

post-operative nausea/vomiting-operative nausea and vomiting. There is much literature

surrounding the benefits of decreasing post-operative nausea and vomiting, but less

information on how to manage it. For this reason, future research should focus on patient

characteristics such as age, gender, and comorbidities which could potentially provide

guidance for management of post-operative nausea and vomiting (Deitrick et al., 2015). In the

future, it would be very beneficial to be able to collect and analyze data regarding age ranges

affected by post-operative nausea and vomiting.

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References

Deitrick, C. L., Mick, D. J., Lauffer, V. L., Prostka, E., Nowak, D., & Ingersoll, G. (2015,

February). A Comparison of Two Differing Doses of Promethazine for the Treatment of

Postoperative Nausea and Vomiting. Journal of Perianesthesia Nursing, 30(1), 5-13.

McLaughlin, M. (2010). Perianesthesia Nursing Standards and Practice Recommendations.

New Jersey: American Society of Perianesthesia Nurses.

Sites, D. S., Johnson, N. T., Miller, J. A., Torbush, P. H., Hardin, J. S., Knowles, S. S., Creech

Tart, R. (2014, February). Controlled Breathing With or Without Peppermint

Aromatherapy for Postoperative Nausea and or/Vomiting Symptom Relief: A

Randomized Controlled Trial. Journal of Perianesthesia Nursing, 29(1), 12-19.

Sullivan, M., & Woodbury, G. (2015). Interactive Statistics: Informed Decisions Using Data.

Boston, MA: Pearson.