Anesthetic and cardiovascular effects of balanced anesthesia using constant rate infusion of midazolam-ketamine-medetomidine with inhalation of oxygen-sevoflurane (MKM-OS anesthesia) in horses.

This study examines the effects of a specific anesthetic combination (MKM-OS) on the cardiovascular health and anesthetic responses of horses. The researchers found that this approach showed promising results for maintaining stable cardiovascular health and efficient recovery times in equine surgery.

Anesthetic Effects of MKM-OS

• The research revolves around the anesthetic and cardiovascular effects of a mixture of midazolam, ketamine, and medetomidine (MKM) administered with sevoflurane in oxygen (OS). This study aims to determine the effectiveness and side effects of this anesthesia technique, dubbed MKM-OS anesthesia, in horses.
• The anesthetic effects were measured through the required concentrations of sevoflurane needed to maintain surgical anesthesia, with an observed average of 1.7%. This percentage refers to the end-tidal (final exhaled breath) concentration of sevoflurane.
• These effects were observed in six healthy thoroughbred horses where surgical procedures were conducted on their right carotid artery while they were under MKM-OS anesthesia. Following cessation of anesthetic drugs, recovery period ranged from 23 to 44 minutes.

Cardiovascular Effects of MKM-OS

• Cardiovascular effects were evaluated by checking heart rate and arterial blood pressure, which averaged between 23-41 beats per minute and 70-112 mmHg respectively.
• Additionally, measures like cardiac output, cardiac index, stroke volume, and systemic vascular resistance were considered to understand the cardio-vascular impact. These aspects were studied while the horses were in two distinct positions – left lateral recumbency (LR) and dorsal recumbency (DR).
• The findings showed that cardiac output and index were maintained between 70-80% in LR and 65-70% of baseline values in DR. Stroke volume remained between 75-85% in LR and 60-70% in the DR position. Additionally, systemic vascular resistance remained largely unchanged regardless of the horse’s position, suggesting cardiovascular stability throughout the surgery.

Implications of the Study

• The conclusions drawn from the research indicate that MKM-OS anesthesia may be beneficial for extended equine surgeries. The method appeared to keep cardiovascular depression to a minimum in both lateral and dorsal recumbency, promoting stable surgical conditions.
• However, further research and clinical trials might be required to consolidate these findings before this technique can be widely implemented in veterinary practice.