Intravenous ondansetron to prevent hypotension during cesarean section under spinal anaesthesia

Abstract

Background: Spinal anesthesia for cesarean section (CS) is associated with common side effects like hypotension and bradycardia. Ondansetron, a 5HT3 receptor antagonist, inhibits Bezold-Jarish reflex and has been found to be effective for prevention of spinal-induced hypotension for elective cesarean section. Aims: The aim of this study was to evaluate the effect of two different doses of ondansetron as prophylaxis to prevent hypotension during spinal anesthesia for caesarean section. Materials and Methods: This prospective randomized double-blinded controlled study was conducted on 150 full-term parturients undergoing CS under spinal anesthesia, who were divided into three groups, receiving saline or different drug doses: Group C: 0.9% Normal Saline 10 ml; Group O4: 4 mg Ondansetron in 8 ml NS; or Group O8: 8 mg Ondansetron in 6 ml NS, 5 min before spinal anesthesia. All the patients were monitored for blood pressure, heart rate, vasopressor requirement, and side effects. Hemodynamic variables and demographic data were compared by analysis of variance (ANOVA) and Chi-square test was used for analyzing adverse effects and P value <0.05 was considered significant. Results: Intraoperative incidence of hypotension was significantly high (P < 0.001) in group C (58%) as compared to group O8 (16%) and group O4 (31.25%) but comparable between ondansetron groups (O8 vs. O4) (P = 0.074). Total requirement of ephedrine (mg) was significantly higher (P < 0.01) in group C (5.02 ± 4.95) as compared to group O8 (1.2 ± 3.20) and O4 (3.00 ± 4.88). It was found to be significantly higher (P = 0.034) in group O4 when compared with group O8. Mean HR, SBP, DBP, MAP was decreased more in group C at different time intervals. Conclusions: Prophylactic intravenous ondansetron reduced the incidence of hypotension and requirement of vasopressors in parturients undergoing CS under spinal anesthesia, with a further decrease in requirement of vasopressor in Group O8.