Evaluation of cardiovascular effects of total intravenous anesthesia with propofol or a combination of ketamine-medetomidine-propofol in horses.

The research investigates the cardiovascular impact of two types of total intravenous anesthesia (TIVA) – propofol-based (P-TIVA) and propofol, ketamine, and medetomidine-based (KMP-TIVA) – on thoroughbred horses. Findings suggest that both methods maintain cardiovascular function within acceptable limits, but marked differences are noted in heart rate and cardiac index behavior.

Study Design and Implementation

• The experiment was conducted on five Thoroughbreds horses.
• Each horse was separately anesthetized for four hours using both the P-TIVA and KMP-TIVA methods.
• For the P-TIVA method, a loading dose of propofol was implemented, and anesthesia was retained using a steady infusion of propofol. On the other hand, KMP-TIVA method involved a combination of propofol, ketamine, and medetomidine.
• During the duration of anesthesia, artificial ventilation was consistently controlled.
• Before the administration of medication and at 30-minute intervals during anesthesia, cardiovascular measurements were determined.
• The recovery period after anesthesia was carefully observed and scored.

Observations and Findings

• Both P-TIVA and KMP-TIVA proved to be effective in maintaining the cardiovascular function of the horses within an acceptable range.
• The heart rate fluctuated between 30 to 40 beats per minute, and the mean arterial blood pressure was observed to be over 90 mm Hg during anesthesia.
• A significant observation was that heart rates were lower for horses anesthetized with KMP-TIVA as opposed to those anesthetized with P-TIVA.
• The cardiac index reportedly decreased considerably, reaching a low of 65% of the baseline values after 90 minutes in KMP-TIVA. In contrast, P-TIVA enabled the maintenance of the cardiac index between 80% and 90% of base values.
• Stroke volume and the systemic vascular resistance were comparably preserved irrespective of the anesthesia method used.
• Several spontaneous limb movements were observed with P-TIVA, whereas no movements occurred with KMP-TIVA.

Conclusion

• Both P-TIVA and KMP-TIVA are effective and safe methods for anesthetizing horses, managing to keep cardiovascular metrics within acceptable limits in artificially ventilated situations.
• It was also revealed that the decreased cardiac output during KMP-TIVA can be mostly attributed to lower heart rates.