The influence of ondansetron on hemodynamic stability after subarachnoid anesthesia in the elderly

Background: Spinal anesthesia (SA) is widely utilized in elderly patients due to its benefits, such as reduced postoperative morbidity and decreased opioid requirements. Despite these advantages, SA-induced hypotension (SAIH) is a significant concern, especially in geriatric patients with compromised cardiovascular function. The Bezold-Jarisch reflex (BJR), which mediates bradycardia and hypotension, plays a crucial role in SAIH. Objective: This review aims to evaluate the effectiveness of prophylactic intravenous ondansetron in preventing hypotension and a decrease in cardiac output following SA in elderly patients undergoing elective surgery. Mechanism of Action: Ondansetron, a 5-HT3 receptor antagonist, is commonly used to prevent nausea and vomiting. However, 5-HT3 receptors also participate in cardiovascular reflexes, particularly in the activation of BJR, leading to hemodynamic instability. By blocking these receptors, ondansetron may mitigate the incidence of SAIH by reducing vagally mediated bradycardia and vasodilation. Clinical Evidence: Numerous studies have investigated the role of ondansetron in stabilizing blood pressure and heart rate after SA. While earlier trials primarily focused on obstetric populations, recent research suggests that ondansetron effectively reduces SAIH, bradycardia, and vasopressor requirements in elderly patients undergoing non-obstetric surgeries. A mixed-population meta-analysis of 25 randomized controlled trials confirmed ondansetron's ability to reduce the incidence of SAIH and bradycardia, with a decreased need for vasopressor interventions. Conclusion: Current evidence suggests that prophylactic ondansetron administration may enhance hemodynamic stability in elderly patients undergoing SA, potentially reducing the need for vasopressor support. Further large-scale studies are required to establish standardized dosing protocols and confirm long-term benefits in this population.