Effects of prophylactic ondansetron on spinal anesthesia-induced hypotension: a meta-analysis

Background A range of strategies including physical interventions, intravenous fluids and vasopressor drugs have been used to minimize or prevent spinal anesthesia-induced hypotension. Recent studies suggest that ondansetron, a commonly used antiemetic, also affects hypotension. This systematic review investigated the effects of prophylactic ondansetron on hemodynamic changes following spinal anesthesia. Methods Medline, Embase, Cochrane Library databases and www.clinicaltrials.gov were searched for randomized controlled trials studying the effects of ondansetron on hemodynamic changes induced by spinal anesthesia. The primary outcome was hypotension. Relative risk (RR) or mean difference, with 95% confidence intervals (CI), were used to analyze outcomes. Results Ten randomized controlled trials with 863 patients were included in the analysis. Prophylactic ondansetron reduced the incidence of spinal anesthesia-induced hypotension in both obstetric and non-obstetric patients. The RR of spinal anesthesia-induced hypotension after ondansetron administration was 0.53 (95% CI 0.32 to 0.86) in obstetric patients and 0.16 (95% CI 0.05 to 0.51) in non-obstetric patients. There was significant heterogeneity among obstetric studies (I 2 = 71%). Ondansetron also reduced the incidence of bradycardia, nausea and vomiting after spinal anesthesia with RRs of 0.27 (95% CI 0.16 to 0.47), 0.24 (95% CI 0.14 to 0.42) and 0.48 (95% CI 0.08 to 3.08), respectively. The doses of ephedrine and phenylephrine required to treat hypotension were reduced by ondansetron with mean differences of −2.35mg (95% CI −4.14 to −0.55mg) and −31.16μg (95% CI −57.46 to −4.87μg), respectively. Conclusion This review suggests that prophylactic ondansetron reduces the incidence of spinal anesthesia-induced hypotension and vasopressor consumption in both obstetric and non-obstetric patients. In addition, ondansetron can also reduce related adverse outcomes such as bradycardia, nausea and vomiting. However, given the relatively large heterogeneity and small sample sizes in current studies, further large and strict randomized clinical trials investigating the effects of ondansetron on spinal anesthesia-induced hemodynamic changes and side effects are still needed, especially among obstetric patients.