Comparison between mephentermine and ondansetron for the prevention of post spinal hypotension: a prospective randomized trial

Background and Aims: Spinal anesthesia is a technique often associated with side effects like hypotension and bradycardia. Recent studies have shown that the use of ondansetron leads to a decreased incidence of hypotension induced by spinal anesthesia. This prospective, randomized, controlled, double-blind study was done to compare the efficacy of the prophylactic use of intravenous (IV) ondansetron and mephentermine on post-spinal hypotension. Methods: A total of 130 patients were randomly allocated to one of two groups: Group O received 4 mg IV ondansetron and Group M received 6 mg of IV mephentermine. All patients received spinal anesthesia using 3 mL of 0.5% hyperbaric bupivacaine. Assessment of blood pressure and heart rate (HR) was done for 30 minutes after spinal anesthesia was performed. Quantitative data were analyzed using ANOVA tests and qualitative data were analyzed using the Chi-square tests. Results: Both groups were comparable regarding demographic data. Mean arterial blood pressure (MAP) in Group O was lower than Group M at 5 to 25 minutes and difference of MAP between the two groups was > 20% of baseline values (p < 0.05). HR was comparable between groups. No statistically significant differences were seen in side effects between the two groups. Conclusion: Our study shows that the preemptive use of both ondansetron and mephentermine significantly decreases the incidence of post-spinal hypotension.