The incidence of postoperative nausea and vomiting (PONV) ranges between 30-80% depending on patient characteristics and surgical/anesthetic procedure ⁽¹⁾. PONV is not only distressing to the patients but is also associated with significantly longer stay in the post-anesthesia care unit (PACU) ⁽²⁾. It is therefore essential to identify patients at high risk for PONV. This enables targeting prophylaxis to those who will benefit most from it rather than adopting universal PONV prophylaxis that is not cost effective, is unlikely to benefit patients at low risk for PONV and would subject them to potential side effects of antiemetic agents. ⁽¹⁾ formulated a simplified PONV risk score that includes four independent predictors: female gender, non-smoking status, history of PONV or motion sickness, and need for postoperative intravenous opioids. When 0, 1, 2, 3, or 4 of these predictors are present, the patient’s risk is approximately 10%, 20%, 40%, 60%, or 80%, respectively. However, ⁽¹⁾ had given same weightage to all these four predictors without considering that each of these predictors is differently proportional to the odds ratios of PONV associated them. 

Over a decade later ⁽⁴⁾ reported that some of these predictors are associated with increased risk of PONV as compared to others. Based on the proportion of the four predictors in the pie chart of ⁽⁵⁾ we allocated numerical scores of 3, 2, 2, 2, 1, and 1 (maximum 11 points) to female sex, laparotomy/ laparoscopic procedure, volatile anesthetic, history of PONV, non-smoker status, age < 40 yr, and intraoperative narcotic use respectively. The aim of this study was to identify the cumulative score of these 11 points in patients undergoing general anesthesia and correlate with the incidence of PONV.

After approval by the Department Management Board, we enrolled 40 consecutive patients of either sex aged 20–60 years, who had to undergo elective surgery of 1-2 hr duration under general anesthesia between 1st October-1st November 2020. The exclusion criteria were patients with ASA physical status ≥ III, with pregnancy or cognitive dysfunction, patients undergoing neurosurgery or having inconsistent data. Each patient was evaluated for the six predictors: female sex, laparotomy/ laparoscopic procedure, volatile anesthetic, history of PONV, non-smoker status, age < 40 yr, and intraoperative narcotic use and given scores of 3, 2, 2, 2, 1, and 1 respectively. Individual predictor scores and their cumulative score were recorded. 

None of the patients received preoperative sedatives, anxiolytics or analgesics. Anesthesia was induced with propofol (1.5-2 mg/kg) and fentanyl (1.5-2 μg/kg). Relaxation for tracheal intubation was achieved using cisatracurium (0.15 mg/Kg). Following tracheal intubation, the lungs were ventilated so as to maintain EtCO2 between 35 and 40 mmHg in 50% oxygen + 50% nitrous oxide at a total flow of 2 L/min with sevoflurane (2-3%) as the inhalational agent.  Any hypotension (MAP < 60 mmHg) was treated with intravenous phenylephrine or ephedrine. All patients received 4-8 mg of intravenous dexamethasone intraoperatively. No other antiemetic was administered. At the conclusion of surgery, residual neuromuscular block was reversed with a mixture of 2.5 mg neostigmine and 0.4 mg glycopyrrolate. Patients were nursed in the recovery room for approximately 30 minutes before discharge to the ward. The nursing staff in the recovery room noted all episodes of PONV in the study proforma and intimated the attending anesthesiologist for advice. Postoperatively, patients who complained of PONV were administered ondansetron 4-8 mg IV. Patients were discharged to the ward after they were comfortable and had no more PONV. 

Data in the tables have been presented as numbers and percentages. We could not carry out any statistical analysis due to the small sample size.

The mean age of our patients was 32.2 yr with a preponderance of male patients (Table 1).

Table 1: Demographic data of the patient.

Yr= year, ± SD= Standard deviation, %= Percentage

Majority of our patients had a score between 6-8. The incidence of vomiting did not show any correlation with the PONV cumulative risk score that we had developed (Table 2).

Table 2: Correlation of cumulative score with the incidence of vomiting.

No. of pts= Number of patients

Table 3 shows that the incidence of PONV in our female patients and those who had past history of PONV was 33%. Amongst the 6 predictors that we evaluated in this series, age less than 40 had the least predictor value. 

Table 3: Correlation of individual score with the incidence of PONV.

No. of pts= Number of patients

Overall incidence of PONV in this study was 20.8% (5/24 patients). Our analysis shows that in patients undergoing various types of surgical procedure under a uniform general anesthesia, the cumulative risk score of six predictors having different weightage for PONV does not reliably predict incidence of PONV. However, the result may be different if the study is carried on a larger sample size. We did find a correlation between higher incidences of PONV in female patients as compared to other predictors that we analyzed. This justified our allocation of maximum point to female sex in our scores. Our result suggests that female patients undergoing elective surgery under general anesthesia may benefit from multimodal approach with combination of pharmacological and non-pharmacological prophylaxis rather than using dexamethasone alone.

As a consequence of our findings, we cannot suggest a modification or change of the prophylactic antiemetic treatment on the basis of our cumulative PONV risk score. One approach would be to continue prophylactic antiemetic treatment on the basis of number of predictors present such as female gender, prior history of PONV, nonsmoking, inhalation agent and the use of postoperative opioids because recent meta-analysis and guideline favors them. Another approach would be to avoid volatile anesthetics entirely in female patients who carry maximum risk of PONV by using a total intravenous anesthetic technique with propofol, which has been shown to be associated with significantly less PONV.

We had included patients between 20-60 year of age in this study. Other studies too opted to study this age group (1). The sample size of our study was small. This can be attributed to Covid 19 pandemic times when elective surgeries are few in numbers.

There are several limitations to our study. First, the sample size was relatively small secondary to reduced number of elective surgeries during COVID-19 pandemic times. Second, we did not administer PONV prophylaxis other than dexamethasone as they could mask PONV. This way we could keep the cause-and-effect relationship nearly identical in all patients. Third, the study subjects were limited to 20–60-year age range; therefore, it is unclear whether this result can be applied to other age groups. Lastly, only one combination of general anesthetic was studied, and the effects of other combinations were not assessed. 

In conclusion, this small sample sized study did not reveal any positive correlation between PONV risk score to the actual incidence of nausea and vomiting. Female sex and history of PONV were noted to carry the highest risk of PONV.

Conflict of Interest: No

Funding: No funding sources

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