The effect of intravenous ondansetron on maternal spinal-induced hypotension in preeclamptic patients undergoing caesarean delivery

BACKGROUND: Prophylactic vasopressor infusions have been recommended for preventing spinal-induced hypotension during caesarean delivery in normotensive patients, but they should be used with caution in patients with preeclampsia due to concerns about exacerbating their haemodynamic instability. Ondansetron has been reported to effectively reduce the incidence of hypotension and decrease the need for vasopressors without causing significant adverse effects in both obstetric and nonobstetric patients undergoing spinal anaesthesia. Nevertheless, evidence regarding its use specifically in patients with preeclampsia remains limited. OBJECTIVE: This study aimed to evaluate the efficacy of ondansetron in preventing spinal anaesthesia-induced hypotension in preeclamptic patients undergoing caesarean delivery. DESIGN: A prospective, double-blinded, randomised clinical trial. SETTING: Single university hospital. PARTICIPANTS: One hundred and twenty preeclamptic patients were enrolled and allocated to Group O and Group C. INTERVENTIONS: Patients in Group O receive intravenous ondansetron (4 mg 2 ml -1 ) or in Group C receive 0.9% saline placebo (2 ml) 10 min before spinal injection. MAIN OUTCOME MEARSURES: The primary outcome of the study was the incidence of hypotension. Secondary outcomes included consumption of phenylephrine, the incidence of side effects, and neonatal outcomes. RESULTS: The incidence of spinal anaesthesia-induced hypotension was higher in Group C than in Group O (55 vs. 30%, mean difference: 25%, 95% CI, 8.4 to 43.9%; P = 0.0009). The relative risk of hypotension associated with or without intravenous ondansetron administration was 0.55 (95% CI, 0.34 to 0.84). CONCLUSION: The intravenous administration of 4 mg of ondansetron can effectively reduce the incidence of spinal anaesthesia-induced hypotension, and consequently decrease the requirement for phenylephrine in patients with preeclampsia undergoing caesarean delivery. TRIAL REGISTRATION: ChiCTR2400080284.