This study was designed to investigate the incidence of postoperative nausea and vomiting to ascertain the degree of discomfort after everyday surgery with modern anesthetic and surgical techniques. Our finding has shown that the incidence of PONV is 27.4% at JUMC, which indicates that the occurrence of PONV in this setup is high. Out of 368 study patients, 267(72.6%) were free of the complication. These findings are in line with studies done in South Africa which showed the incidence of PONV among African groups was 27%. (23) This does not differ much from what studies done in Malawi which showed the incidence of PONV was 29%. (24)
This finding was low when compared with other studies done in Africa and Asia. Consequently, studies conducted in Nigeria (25), Uganda (26), Tanzania (27) and Ghana (28), found the incidence of PONV 41%, 40.7%, 41.4%, and 34% respectively. In India (7) and Singapore (29), it was found to be 33.3% and 34.1%, respectively. This might be due to the techniques used in their studies to measure PONV. They used traditional methods (absolute counts, Likert scales, visual analogue scales (VAS), and treatment response). They just defined PONV as having at least one episode of nausea, vomiting or both within 24 hours postoperatively. Due to this, they might be included in the PONV condition, which was not clinically significant. However, this study has used a recently developed PONV Intensity Scale, which is believed to be a valid, reliable, and responsive measure of clinically important PONV. (20) On the other hand, this study finding is high when compared with the studies in developed countries. A recent study in South Korea by J.Choi found the incidence of PONV was 23%.(30) Similarly, in Turkey it was found to be 25%.(31) This difference in incidence might be due to anesthesia and surgical technique differences and study design.
In this study, the incidence of PONV was higher in the female patients. Among the females, 40.5% had PONV compared to 11% in males. The female gender increased the likelihood of PONV by four times, and it was the strongest predictor of PONV with AOR of 4.065 (2.090–7.906). This finding was consistent with what has previously been reported from studies done elsewhere. Morino, in Japan found that women were significantly more likely to develop PONV (four times) than men and suggested that women be considered for prophylactic antiemetic therapy.(32) Similarly, N. Rodseth, in South Africa found that women patients were more likely to develop PONV than men and suggested for prophylactic antiemetic therapy.(23) A descriptive study conducted at Toronto Hospital, Canada, found that women had a nearly two fold higher rate of PONV than male.(33) In the same way, a 2012 systematic review study of PONV from San Francisco (USA), identified being a female as strongest patient specific predictor.(34) This is due to vomiting center in females is influenced by the endocrine or hormonal environment.(35)
A previous history of PONV or motion sickness was also strongly associated with PONV. Among the seventeen six patients who had PONV previously, 42.9% had an incidence of PONV while only 18.7% had developed in the group with no history of PONV. This group of patients was three times more likely to have PONV with AOR of 2.836 (1.582–5.083). Similar findings have been noted in other studies. In the study done by Morino, C. C. Apfel (32) and N. Rodseth, in South Africa (23), previous history of PONV or motion sickness was a strong risk factor with AOR of 3.65 (2.52–5.30) and 2.6 (1.8–3.7), respectively. Similarly, it was the second strongest predictor of PONV in a Korean predictive model for post-operative nausea and vomiting study with an odds ratio of 2.4.(36) This is because of genetic factors to determine sensitivity to motion sickness (37) and because individuals with a history of these factors have already established reflex arch for vomiting.(9, 38) Other preoperative factors such as, age of patient, BMI, pre-operative anxiety, history of migraine headache and smoking history is reported to affect the prevalence of PONV, but in this study these factors were not found to be independent predictors of PONV after multiple logistic regression.
Consequently, the duration of anesthesia was one of intraoperative independent predictors of PONV. It was found patients who had a duration of anesthesia greater than sixty minutes were three times more likely developed PONV in comparison than those durations of less than sixty minutes, with an adjusted odds ratio of 2.974 (1.491–5.933). This result was in agreement with what has previously been reported from different studies.(8, 33, 34) One study indicated that for every 30-minute increase in surgical time, there was a 59% rise in the baseline risk of PONV.(33) Similarly, in a Korean Predictive Model for postoperative nausea and vomiting study, duration of anesthesia was a predictor of PONV with the odds ratio of 1.9 for the anesthesia time longer than 1 hour.(36) This is due to prolonged surgery increases exposure to anesthetic agents, use of intraoperative opioids, and increased exposure to hemodynamic instability which increases incidence of PONV.(9)
Output of multiple logistic regression analysis also revealed that among the type of surgery, only gynecologic surgery was significantly associated with PONV as an independent predictor of PONV. In patients who underwent gynecologic surgery, the incidence of PONV was four times more likely occurred than those with non-gynecologic surgeries with AOR of 3.782(1.156–12.373). This result was in agreement with what has previously been reported from other studies. In a 2012 cross-sectional study at the university of Gondar teaching hospital, northwest, Ethiopia, gynecology operation was identified as independent predictor of PONV with AOR of 2.58 (1.24–5.39).(39) This might be due to stimulation of vagal afferents nerves during gynecologic surgery manipulation that result in activation of vomiting center.(4,48) Moreover, it might be because of patients are all females.(34) In contrast to this, a 2012 systematic review, were stated that “there is no or insufficient evidence for type of surgery to be an independent risk factor for PONV.(34) This is possibly due to differences in study design and study population. On the other hand, despite intraoperative factors such as, type of anesthesia, incidence of intraoperative hypotension, administration of neostigmine and intraoperative use of opioids were included in the final model, they were not independent predictors of PONV after multiple logistic regression.
Postoperative administration of opioid was the only post-operative factor that was identified as an independent predictor of PONV after multiple logistic regressions. Among 204 patients who had taken postoperative opioids, 37.7% had PONV compared to 14.6% of those who hadn’t taken. In patients who had received postoperative opioids, the incidence of PONV was two times more likely developed when compared with those who hadn’t received postoperative opioids, with AOR of 2.333 (1.221–4.457). This was in line with findings of studies done elsewhere. Roberts et al, in Australia found postoperative opioid use to significantly (p = 0.025) affect the incidence of PONV, stating that postoperative opioid administration increases the incidence of PONV in dose dependent manner.(40) Similarly, in a 2012 systematic review study of PONV from San Francisco (USA), it was the strongest anesthesia-related predictor of PONV.(34) The reason for this is due to the fact that opioids directly stimulates the Chemoreceptor Trigger Zone and vestibular apparatus, and also decreases motility of the gut increasing the incidence of PONV.(4)
The strength of this study was that we have used a recently developed technique (linear PONV Intensity Scale), a reliable technique which is used to identify clinically significant PONV. Limitations of the Study include some perioperative factors were not well documented