Efficacy of Prophylactic Intravenous Ondansetron for the Prevention of Sympathetic Blockade-Induced Hypotension during Cesarean Section under Spinal Anesthesia

International Journal of Obstetrics and Gynecology | Vol. 14, No. 9, September 2026 | pp. 771–782

DOI: 10.46882/2026/IJOG/000545

Original Research Article

Title: Efficacy of Prophylactic Intravenous Ondansetron for the Prevention of Sympathetic Blockade-Induced Hypotension during Cesarean Section under Spinal Anesthesia

Names of Authors: Emeka J. Obi¹, Funmilayo R. Adeyemi², Zainab H. Dogara¹

Authors’ Affiliations:
¹ Department of Obstetrics and Gynecology, Nnamdi Azikiwe University Teaching Hospital, Nnewi, Nigeria
² Maternal Health Division, Federal Ministry of Health, Abuja, Nigeria

Abstract:
Spinal anesthesia for cesarean delivery routinely induces maternal hypotension and shivering secondary to sympathetic blockade and the Bezold-Jarisch reflex. This double-blind randomized clinical trial investigated the hemostatic efficacy of prophylactic intravenous ondansetron in stabilizing cardiovascular parameters and reducing vasopressor needs. Two hundred healthy women scheduled for elective cesarean delivery were randomized to receive either 4 mg of intravenous ondansetron (n = 100) or a matching saline placebo (n = 100) 5 minutes before the initiation of spinal anesthesia. Vital signs were checked at 2-minute intervals during the first 20 minutes following spinal block. The primary endpoint was the incidence of maternal hypotension (systolic blood pressure < 90 mmHg). The incidence of spinal anesthesia-induced maternal hypotension was significantly lower in the ondansetron group compared to the placebo group (28.0% vs. 52.0%, p = 0.001). Consequently, the mean dose of rescue phenylephrine required to restore baseline blood pressure was significantly lower in the ondansetron arm (1.2 ± 0.4 mg vs. 2.5 ± 0.8 mg, p < 0.001). Ondansetron also reduced the severity of intraoperative nausea and vomiting (4.0% vs. 16.0%, p = 0.004). Neonatal outcomes measured via umbilical artery gas parameters and 5-minute Apgar scores were excellent and equal across both arms (p > 0.05). Prophylactic administration of 4 mg intravenous ondansetron effectively minimizes sympathetic blockade-induced hypotension and limits overall vasopressor dependencies during cesarean sections under spinal anesthesia.

Keywords: Spinal Anesthesia; Cesarean Section; Hypotension; Ondansetron; Phenylephrine; Bezold-Jarisch Reflex.

Manuscript Timeline: Received: August 10, 2026; Revised: September 04, 2026; Accepted: September 14, 2026; Published: September 25, 2026.

Citation: Obi EJ, Adeyemi FR, Dogara ZH. Efficacy of Prophylactic Intravenous Ondansetron for the Prevention of Sympathetic Blockade-Induced Hypotension during Cesarean Section under Spinal Anesthesia. International Journal of Obstetrics and Gynecology. 2026; 14(9): 771–782.

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