Metabolic, hormonal, and hemodynamic changes during dopamine infusions in halothane anesthetized horses.

This research explores the metabolic, hormonal, and cardiovascular impacts of dopamine infusions in horses under anesthesia. The findings suggest that high-dose dopamine infusion can cause significant changes in plasma nonesterified fatty acids, blood glucose, blood lactate and insulin levels, but might also cause heart complications.

Scope of the Study

• The focus of the study was on evaluating the changes in selected metabolites, hormones, and cardiovascular variables in halothane anesthetized horses during and post dopamine infusion.
• In the experiment, dopamine was infused at a low rate (5 micrograms/kg/min) and a high rate (10 micrograms/kg/min) for an hour each, and the horses were monitored for an additional hour after the infusion.

Results and Observations

• Findings from the study indicated that plasma cortisol, a hormone responsible for stress response, increased two folds in the group of horses receiving low-dose dopamine but remained constant in the high-dose group.
• There were significant increases in plasma nonesterified fatty acids, blood glucose, blood lactate, and plasma insulin in the high-dose group. These changes suggest metabolic and hormonal shifts induced by dopamine.
• No significant differences were observed in heart rate, systolic, diastolic, and mean arterial blood pressure between the low and high infusion groups.
• Exceptionally, some horses in high infusion group exhibited arrhythmias – irregular heartbeats. One horse even experienced ventricular fibrillation, a severe cardiac rhythm disturbance that led to its death.

Implications of the Study

• On the basis of the reported findings, it can be inferred that high-dose dopamine infusion can significantly affect metabolic and hormonal states. However, it may also predispose horses to cardiac risks.
• The hormonal changes, especially the increase in cortisol levels, are often interpreted as signs of “stress response” in anesthetized horses. Yet, these changes need to be interpreted with caution as they may be influenced by other agents, such as dopamine used for maintaining cardiovascular stability.
• Overall, this study underscores the importance of dose considerations and careful physiological monitoring when administering dopamine to anesthetized horses.