# Evaluation of the Cardiovascular and Serotonergic Modulatory Effects of Ondansetron in Healthy Dogs Under Anesthesia

## TL;DR

This study found that ondansetron, a drug typically used to prevent nausea, can help maintain stable heart function in dogs during anesthesia without causing excessive heart rate or stress.

## Contribution

The study introduces ondansetron as a potential safer alternative to atropine for autonomic modulation during canine anesthesia.

## Key findings

- Ondansetron maintained stable cardiovascular parameters without bradycardia or tachycardia.
- Atropine caused sustained heart rate increases and elevated NT-proBNP levels post-surgery.
- Ondansetron showed no significant myocardial stress as indicated by unchanged NT-proBNP levels.

## Abstract

Maintaining autonomic and cardiovascular stability during anesthesia is essential for the safety of dogs. Atropine is commonly administered to prevent vagally mediated bradycardia; however, it may induce excessive sympathetic stimulation, resulting in marked tachycardia and increased cardiac workload. This study evaluated whether ondansetron, a serotonin 5-hydroxytryptamine type 3 (5-HT3) receptor antagonist primarily used as an antiemetic, could serve as a safer anesthetic adjuvant for autonomic modulation during anesthesia. Healthy dogs undergoing elective surgery received atropine, ondansetron, or no autonomic-modulating drug. Heart rate, blood pressure, respiratory rate, and a cardiac biomarker of myocardial stress, N-terminal pro–B-type natriuretic peptide (NT-proBNP), were assessed before, during, and after anesthesia. Dogs treated with ondansetron maintained stable cardiovascular parameters without developing bradycardia or excessive tachycardia, whereas atropine administration was associated with a sustained increase in heart rate and a postoperative rise in NT-proBNP concentrations. 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.

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.