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 the BJR. the aim was to study the effect of intravenous ondansetron on maternal hemodynamics.

Methods 150 healthy parturients scheduled for elective caesarean section were randomly allocated into two groups of 75 each to receive either 4 mg ondansetron diluted to 10 ml of 0.9% normal saline or 10 ml of 0.9% normal saline 10 minutes before initiation of SAB. Haemodynamic parameters were studied from time of administration of the study drug up to the time of delivery.

Results Both the groups were comparable to each other with respect to baseline haemodynamic parameters. SAB induced fall in SBP, DBP and MAP was significantly less in the ondansetron group as compared to placebo from the time of initiation of SAB up to 12 minutes of surgery time (p<0.05). However, the difference in HR between both the groups was not statistically significant. the total use of vasopressors was less in ondansetron group as compared to placebo (p<0.05). Better neonatal outcomes were observed in the ondansetron group.

Conclusions Intravenous ondansetron premedication can successfully attenuate SAB induced fall in SBP, DBP and MAP in parturients undergoing elective cesarean sections.