Background and Aims: Spinal anesthesia for elective cesarean delivery has a high incidence of hypotension (50-80%) caused by sympathetic inhibition and activation of the Bezold-Jarisch reflex. This double-blind randomized study was designed to determine whether preoperative administration of 4 mg of intravenous Ondansetron can stabilize hemodynamics in patients undergoing elective cesarean section.
Methods: Sixty ASA I pregnant women scheduled for elective cesarean delivery were randomized to receive IV Ondansetron (n=30) or placebo (n=30) 3 minutes before spinal anesthesia (12.5 mg hyperbaric bupivacaine + 2.5 µg sufentanil). Hemodynamic parameters (heart rate and blood pressure trends) were primary outcomes; secondary outcomes included ephedrine requirements and adverse events. Independent t-tests, ANOVA, Mann-Whitney U tests, and Chi-square tests (SPSS v22; α = 0.05) were used in the statistical analysis.
Results: Ondansetron was associated with significantly more shivering (46.7% vs. 17.2%; P<0.05). The Ondansetron group maintained a higher total heart rate (93.50 ± 1.742 vs. 88.34 ± 1.673 bpm; P=0.044), with significant increases at 25, 45, and 120 minutes (P<0.05). Although diastolic blood pressure/mean arterial pressure was higher at later periods (75/105 min; P<0.05), systolic blood pressure in the Ondansetron group was lower at 5 minutes (108.81 ± 16.072 vs. 118.86 ± 16.072 mmHg, P<0.01). Overall, there were no net differences in blood pressure. The Ondansetron group required ephedrine more frequently (77.4% vs. 58.6%), although they had the same mean dose (14.16±7.019 vs. 12.35±5.036 mg; P=0.368). Ondansetron caused significantly more shivering (46.7% vs. 17.2%; P<0.05).
Conclusion: Prophylactic Ondansetron raises heart rate and momentarily increases late-phase BP but worsens early hypotension and shivering. It offers no overall hemodynamic benefit and may raise vasopressor requirements, so caution is advised in clinical use.