Effect of intravenous ondansetron on maternal hemodynamics during elective caesarean section under subarachnoid block

Background and Aims: The Bezold-Jarisch reflex (BJR) is considered to contribute to subarachnoid block (SAB)-induced hypotension and bradycardia and is mediated by serotonin receptors (5-HT3 subtype). Ondansetron, a 5-HT3 receptor antagonist, is assumed to block the effect of serotonin and inhibit BJR. The aim was to study the effect of intravenous ondansetron on maternal hemodynamics. Materials and Methods: The study was conducted on 150 healthy parturients scheduled for elective caesarean section under SAB who were randomly allocated into two groups of 75 each to receive either 4 mg ondansetron or 0.9% normal saline 10 min before initiation of SAB. Hemodynamic parameters were studied from the time of administration of the study drug upto the time of delivery of baby. Results: Both the groups were comparable to each other with respect to baseline hemodynamic parameters. SAB-induced fall in systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) was significantly less in the ondansetron group when compared with placebo from the time of initiation of SAB upto 12 min of surgery time (P < 0.05). However, the difference in heart rate between both groups was not statistically significant. The total use of vasopressors was significantly low in ondansetron group when compared with placebo (P < 0.05). Better neonatal outcomes were observed in the ondansetron group. Conclusion: Intravenous ondansetron premedication can successfully attenuate SAB-induced fall in SBP, DBP, and MAP in parturients undergoing elective caesarean sections.