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Abstract
Background:
Spinal anesthesia is commonly employed for elective surgeries but is frequently complicated by hypotension due to sympathetic blockade. Preventing spinal-induced hypotension is clinically important to reduce perioperative morbidity. Ondansetron, a 5-HT3 receptor antagonist, has been proposed to attenuate hypotension by modulating the Bezold–Jarisch reflex.
Objective:
To evaluate the effectiveness of prophylactic ondansetron compared with placebo in preventing spinal-induced hypotension.
Methods:
This quasi-experimental comparative study was conducted in the Department of Anaesthesia, Northwest General Hospital & Research Centre, Peshawar, from October 2024 to March 2025. A total of 108 ASA I–II patients aged 20–50 years undergoing elective urologic, orthopedic, or gynecological surgeries under spinal anesthesia were enrolled and divided into two equal groups. Group A received intravenous ondansetron 6 mg diluted to 20 mL prior to spinal anesthesia, while Group B received 20 mL normal saline as placebo. Mean arterial pressure (MAP) and heart rate were recorded at baseline and at 5-minute intervals for 20 minutes. Hypotension was defined as MAP <80 mmHg or a >20% fall from baseline.
Results:
The incidence of hypotension was significantly lower in the ondansetron group compared to placebo (11.1% vs 35.2%, p=0.003). MAP values at 5, 10, 15, and 20 minutes were significantly higher in the ondansetron group (p<0.001). Requirement for rescue phenylephrine was also reduced (7.4% vs 33.3%, p<0.001).
Conclusion:
Prophylactic ondansetron significantly reduces the incidence of spinal-induced hypotension and vasopressor requirement, improving perioperative hemodynamic stability in elective non-obstetric surgeries.