The effect of ondansetron administration 20 minutes prior to spinal anaesthesia on haemodynamic status in patients undergoing elective caesarean section: A comparison between two different doses.

Background And Aims: Spinal anaesthesia is currently the most common method used for managing patients undergoing elective caesarean sections. Recent meta-analyses have been supporting the use of 5-HT3 antagonists, like ondansetron, to attenuate hypotension induced by spinal block. Various doses of ondansetron were given intravenously five minutes before spinal block. However, a consensus on definitive dose and timing for maximal benefit is yet to be agreed upon.

Methods: Our prospective randomised clinical trial investigated a new approach by administrating intravenous ondansetron 20 minutes before spinal anaesthesia. This work investigated ondansetron effect on both haemodynamic changes and vasopressors use by dividing patients into three groups. The first group O4 (n = 51) received 4 mg ondansetron, the second group O6 (n = 51) received 6 mg ondansetron, and the control group C (n = 50) received normal saline. We recorded systolic blood pressure (SBP), diastolic blood pressure (DBP) and the mean blood pressure (MBP) at different time intervals.

Results: There was no significant difference in blood pressure measurements among the study groups ( > 0.05). The consumption of ephedrine in the control group is higher than both of the ondansetron groups ( > 0.001), with a mean dose of 27.2 ± 20.5 mg of ephedrine for group C, compared to 17.8 ± 14.9 and 14.7 ± 11.3 in O4 and O6 groups, respectively. Episodes of hypotension and number of patients with hypotension were not significantly different among the studied groups ( = 0.07; = 0.96, respectively).

Conclusions: Prophylactic 4 and 6 mg ondansetron given 20 minutes before spinal anaesthesia in caesarean section does not reduce the incidence of hypotension.