Effect of ondansetron on prevention of post-induction hypotension in elderly patients undergoing general anesthesia: A randomized, double-blind placebo-controlled clinical trial

Background: Elderly patients are susceptible to post-induction hypotension. Volume loading and vasopressors for prevention of hypotension in elderly patients may increase perioperative cardiovascular risks. Ondansetron by blocking Bezold-Jarisch reflex (BJR) through inhibition of serotonin receptors has been effective in the prevention of post-spinal hypotension, and bradycardia. Bradycardia frequently accompanies post-induction hypotension in elderly patients, which signifies a possible preventing role for ondansetron. No previous study has evaluated the prophylactic effects of ondansetron for the prevention of post-induction hypotension. Materials and Methods: In this randomized placebo-controlled clinical trial, ondansetron 4 mg was given intravenously to 65 elderly patients, 20 min before induction of general anesthesia, and the rate of post-induction hypotension defined as 25% or more reduction in mean arterial blood pressure, compared with a placebo groups. Results: A total of 114 patients completed the study (58 in ondansetron and 56 in the placebo group). Proportions of post-induction hypotension were 9 (16%) and 25 (45%) in ondansetron and placebo groups, respectively, (P = 0.001). Forty-five patients (40%) developed bradycardia. Rates of bradycardia were not significantly different between two groups. Conclusions: The results of this study show the effectiveness of intravenous ondansetron for prevention of post-induction hypotension in elderly patients. The mechanism of this effect largely is unknown. Role of ondansetron for prevention of post-induction hypotension may not fully understandable by its interaction with BJR, as has been shown in post-spinal hypotension.