The effecT of eThniciTy on The incidence of posToperaTive nausea and vomiTing in moderaTe To high risk paTienTs undergoing general anesThesia in souTh africa: a conTrolled observaTional sTudy

Background: We conducted this prospective controlled observational study to compare the effect of ethnicity on the risk of postoperative nausea and vomiting (ponv) between moderate to high-risk african and non-african patients undergoing general anesthesia. Methods: using apfel score risk factors and predicted length of surgery (>30 minutes), 89 moderate to high risk patients undergoing general anesthesia were recruited in a university hospital between march 2009 and november 2010. Thirty patients in the non-african group and 59 patients in the African group were allocated using an ethnicity self identification questionnaire. intraoperative anesthesia was standardized. ponv was assessed at 0 minutes, 15 minutes, 90 minutes, 180 minutes, and 24 hours. generalized linear mixed effects models was used to determine the effect of ethnicity on ponv. Results: despite similar apfel scores, cumulative incidence of postoperative nausea was higher in the non-african group at 0 minutes (46.67% vs 22.03%, P = 0.019), 15 minutes (70% vs 23.73%, p<0.001) and 90 minutes (36.67% vs 16.95%, P = 0.04). The non-african group had more episodes of vomiting over 24 hours (13.33% vs 1.69%, P = 0.055). non-africans had a 25 times higher reported nausea incidence than africans over 24 hours. Conclusion: The incidence of PONV in non-Africans is significantly higher than in Africans. non-african ethnicity is an independent risk factor for ponv. current risk prediction models may be limited in multi-ethnic populations and further investigations are warranted to examine ethnicity as a risk factor.