Evaluation of the cardiovascular and serotonergic modulatory effects of ondansetron in healthy dogs under anesthesia

Maintaining cardiovascular stability during anesthesia is essential, yet the routine use of atropine to prevent vagally induced low heart rate may impose additional stress on the heart. This randomized, controlled, observer-blinded, clinical study aimed to evaluate whether ondansetron, a selective 5-HT₃ receptor antagonist, could serve as an alternative anesthetic adjuvant to modulate autonomic activity while maintaining cardiovascular stability in dogs. A total of 66 female dogs, with a mean age of 1.5 years and a mean weight of 16–18 kg ASA I, undergoing elective surgery were assigned to three study groups to receive atropine, ondansetron, or no autonomic-modulating drug. Heart rate, arterial pressure, respiratory rate, and NT-proBNP were recorded before, during, and after anesthesia. Dogs treated with ondansetron maintained stable cardiovascular values throughout the procedure, with no episodes of low heart rate or excessive increases in heart rate. In contrast, atropine induced marked and sustained elevation in heart rate and higher arterial pressures. Concentrations of the cardiac biomarker NT-proBNP increased significantly 48 h after surgery in the atropine group but remained unchanged in the ondansetron group, indicating the absence of additional myocardial stress. These findings suggest that ondansetron may help preserve autonomic balance during anesthesia while minimizing myocardial stress. Ondansetron could represent a useful component of multimodal anesthetic protocols, particularly in dogs in which excessive cardiac stimulation should be avoided.