Anesthetic and cardiopulmonary effects of total intravenous anesthesia using a midazolam, ketamine and medetomidine drug combination in horses.

This research primarily assesses the impact of a drug combination of midazolam, ketamine, and medetomidine on the anesthetic and cardiopulmonary conditions of horses. The study indicates that the mixture results in acceptable general anesthesia with minor cardiopulmonary depression, but it is suggested that oxygen supplementation is used to prevent hypoxemia.

Research Methodology and Procedure

• The experiment was conducted on 14 horses where they were given anesthesia through an IV injection containing a midazolam, ketamine, and medetomidine drug combination known as MKM-TIVA.
• Medetomidine was used as the pre-anesthetic medication, followed by an injection of ketamine and midazolam. This was then succeeded by the continuous infusion of the MKM drug combination.
• Out of the 14 horses, 9 male horses — 3 thoroughbred and 6 draft — underwent castration while under the effects of the MKM-TIVA. The average period of anesthesia was around 38 minutes and the infusion rate of the MKM drug mixture was 0.091 ml/kg/hr.
• The time taken by the horses to stand after discontinuing the drug was around 33 minutes on average. The recovery was noted as satisfactory for 3 horses and excellent for 6.

Evaluation of Cardiopulmonary Effects

• An additional 5 healthy thoroughbred horses were used for assessing the cardiopulmonary repercussions of the MKM-TIVA. The horses were anesthetized for an hour and given the MKM drug mix at 0.1 ml/kg/hr.
• It was noticed that the cardiac output and cardiac index declined to about 70-80% of the original value. Conversely, the stroke volume increased to 110% and systemic vascular resistance rose to 130% of the baseline value.
• Furthermore, the partial pressure of arterial blood carbon dioxide remained at around 50 mmHg. However, the arterial partial pressure of oxygen dropped to 50-60 mmHg.

Research Conclusion

• Overall, the MKM-TIVA seems to provide clinically acceptable general anesthesia with a slight depression in cardiopulmonary functions in horses.
• Given the reduced arterial partial pressure of oxygen, it is recommended to supplement inspired air with oxygen to prevent the development of hypoxemia.