A clinical study on the effect in horses during medetomidine-isoflurane anaesthesia, of butorphanol constant rate infusion on isoflurane requirements, on cardiopulmonary function and on recovery characteristics.

The study investigates the effects of adding butorphanol to medetomidine-isoflurane anaesthesia on horses. It primarily focuses on the impact on isoflurane requirements, cardiopulmonary function, and recovery factors. However, it concluded that butorphanol did not significantly decrease isoflurane requirements, or influence cardiopulmonary function and recovery in the horses.

Study Design and Methods

• The experiment was a prospective blinded randomised clinical trial involving 61 horses undergoing elective surgery.
• The horses were sedated with intravenous medetomidine; anaesthesia was induced with intravenous ketamine and diazepam, and maintained with isoflurane and a constant rate infusion of medetomidine.
• The horses were divided into two groups: One received butorphanol (Group MB), and the other received saline (Group M). Both the groups received artificial ventilation to maintain end-tidal CO2 levels.
• Lactated Ringer’s solution and dobutamine were administered if required. Gaseous levels, heart rate and mean arterial blood pressure were monitored continuously; pH and blood gases were measured every 30 minutes.
• The recovery of horses was timed and scored for analysis.

Results of the Study

• The study found no significant difference between the two groups in terms of anaesthesia duration, end-tidal isoflurane, mean arterial blood pressure, heart rate, pH, and PaCO2.
• Recovery times and quality of recovery were also similar between the two groups. However, the time it took to remove a breathing tube (extubation) was considerably longer in the group that received butorphanol.
• The researchers concluded that adding butorphanol at the dose used in the study does not decrease isoflurane requirements nor influence cardiopulmonary function or recovery in horses under medetomidine-isoflurane anaesthesia.

Significance of the Study

• The findings of this study provide valuable insights into anaesthesia management in horses.
• Considering butorphanol had no significant impact on variables studied, it could potentially be discarded from anaesthesia protocols, thereby simplifying management and reducing costs.
• However, the longer extubation times in the butorphanol group may suggest possible implications for recovery from anaesthesia, which warrants further research.