Clinical comparison of xylazine and medetomidine for premedication of horses.

The study compares the effects of using either xylazine or medetomidine as a premedication in horses undergoing general anesthesia, discovering that both substances present similar outcomes, although the transition into inhalation anesthesia was smoother when medetomidine was used.

Background

• The research aims to compare the use of two drugs, medetomidine and xylazine, as premedication for horses undergoing general anesthesia. The application of a premedication substance is often practiced to calm animals before undergoing anesthesia.

Methods

• The study involved 40 horses which were split into two groups; 20 were premedicated with medetomidine, and 20 were premedicated with xylazine.
• Following premedication, all horses were anesthetized using a combination of guaifenesin and ketamine. Halothane was used to maintain anesthesia.
• If a horse’s sedation level was insufficient at anesthetic induction, they were given extra doses of medetomidine or xylazine.
• After anesthetic induction, sodium pentothal was used as required to inhibit limb movements.
• Hypotension was treated using dobutamine, while hypoventilation and hypoxemia were treated with intermittent positive-pressure ventilation.
• The research team assessed the quality of anesthetic initiation, maintenance, and recovery, along with the transition to inhalation anesthesia of each horse in both groups.

Results

• The researchers concluded that for the transition to inhalation anesthesia, the horses premedicated with medetomidine had significantly higher scores than the horses premedicated with xylazine.
• There were, however, no significant differences in terms of the other scores, recovery times, and the number of attempts needed for horses to achieve sternal recumbency (being able to lie down) and stand between the two groups.

Conclusions

• The study concluded that medetomidine is suitable for use as premedication for horses undergoing general anesthesia. Its effects on anaesthetic and cardiopulmonary responses were very similar to those produced by xylazine.
• The notable difference was the smoother transition to inhalation anesthesia when horses were premedicated with medetomidine.