Comparison of Two Different Doses of Intravenous Ondansetron with Placebo on the Occurrence of Hypotension and Neonatal Parameters during Spinal Anaesthesia for Elective Caesarean Section

Abstract

Background and Aims: Bezold-Jarish reflex mediated by hydroxytryptamine (5-HT) may potentiate bradycardia and hypotension, during caesarean section under subarachnoid block. Use of ondansetron (5HT antagonist), has been found to obtund this reflex. The aim was to study the effect of different doses of intravenous ondansetron, on the haemodynamic response and the neonatal outcome following Subarachnoid Block (SAB). Methods: One hundred and fifty ASA 1 & 2 patients aged 18-35 years undergoing caesarean section under SAB were divided randomly into three groups in this prospective double-blind study. Group A (n = 50), Group B (n = 50) and Group C (n = 50) received intravenous ondansetron 4 mg, 6 mg and normal saline respectively, just before SAB. Haemodynamic parameters, incidence of hypotension and bradycardia, vasopressor requirements, umbilical cord arterial blood gas analysis and side effects if any were observed. Data was analysed using ANOVA and Chi-Square Test. Results: When compared with Group C, the incidence of maternal hypotension was significantly lower in Groups A and B (p < 0.05). The vasopressor requirement was significantly higher in Group C than in Groups A and B (A = 1.41±2.58, B = 1.54±2.69, C = 2.25±2.94, p = 0.001). The umbilical artery pH was significantly higher in Groups A and B, compared to Group C (A = 7.33±0.042, B = 7.34±0.045, C = 7.30±0.066, p<0.05). Conclusion: Prophylactic administration of ondansetron reduced the incidence of maternal hypotension but 6 mg was not better than 4 mg.