Effect of different prophylactical doses of ondansetron for the hemodynamic stability in patients undergoing cesarean section: a randomized controlled study

Abstract

Background: 5-hydroxytryptamine 3 (5-HT3) receptor antagonists have been reported to reduce post-spinal anesthesia hypotension, though their efficacy remains controversial. We investigated the effect of prophylactic ondansetron on hemodynamic stability in patients undergoing cesarean section following spinal anesthesia. Methods: Patients scheduled for elective cesarean section (n = 120) were randomly allocated to three groups (NS group, 4 mg group, 8 mg group) of 40: those given 4 mL of normal saline (NS), and those given either 4 mg or 8 mg ondansetron (4 mL) before spinal anesthesia. Patient information, maternal systolic blood pressure stability [median performance error (MDPE), median absolute performance error (MDAPE)], the incidence of post-spinal anesthesia hypotension, norepinephrine doses, other adverse events (severe post-spinal anesthesia hypotension, nausea, vomiting, bradycardia, and hypertension), umbilical artery blood gas values, and infant Apgar scores were all recorded. Results: The primary outcomes (median performance error, MDPE and median absolute performance error, MDAPE) were significantly different among the three groups. (p = 0.001, p = 0.002). Compared with the NS group, systolic blood pressure (SBP) was maintained closer to baseline in the 4 mg group (p = 0.003, p = 0.006), as was the 8 mg group (p = 0.011, p = 0.006). There was a significant difference in the incidence of post-spinal anesthesia hypotension among the three groups (p = 0.002). However, only there was a statistical difference between NS and the 8 mg groups in pairwise comparisons (p = 0.001). The doses of norepinephrine, the incidences of other adverse events, umbilical artery blood gas, and Apgar scores were not statistically different between the three groups. Conclusion: Prophylactic 4 mg or 8 mg ondansetron improved hemodynamic stability after spinal anesthesia in cesarean section; however, only 8 mg reduced post-spinal anesthesia hypotension. Clinical trial registration: Clinicaltrials.gov, NCT05475873.