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.