Evaluation of xylazine and ketamine hydrochloride for anesthesia in horses.

This research studied the effects of using a combination of xylazine and ketamine hydrochloride as an anesthetic in horses. The results showed that the drug combination provided good analgesia and mild anesthesia, with stable cardiopulmonary function.

Background and Methods

• The researchers aimed to evaluate the cardiopulmonary effects of a xylazine-ketamine hydrochloride combination on adult horses.
• The xylazine dose of 1.1 mg/kg was administered intravenously, either before or together with ketamine hydrochloride, at a dose of 2.2 mg/kg. The researchers selected this dosage based on previous studies and the known effects of the drugs on equine physiology.

Findings

• Administering the combination of xylazine and ketamine hydrochloride led to excellent analgesia and light anesthesia in all tested horses.
• The animals’ cardiac output, blood pressure, pulmonary arterial pressure, central venous pressure, and pulmonary arterial wedge pressure remained within normal limits, suggesting that the drugs didn’t adversely affect the cardiovascular system.
• There was a sign of developing respiratory acidosis during the anesthesia. This is a condition in which the blood becomes too acidic due to decreased respiration, and it requires careful monitoring.
• Both induction and recovery from anesthesia were reported to be smooth and without signs of excitement.

Complications and Precautions

• Larger dosages of ketamine hydrochloride (6.6 mg/kg), administered after sedation with xylazine, led to undesirable side effects. These included muscular tremors and rigidity, dilated pupils, eye movements, perspiration, high blood pressure, rapid heart rate, and increased rectal temperature during the recovery period.
• Based on these findings, the researchers warned that the sedative properties of xylazine must be apparent before ketamine administration, and excessive ketamine dosages should be avoided. Otherwise, the drug combination can result in severe side effects, making it unsuitable as an anesthetic in horses.

Conclusion

• When used correctly, the combination of xylazine and ketamine hydrochloride proved to be a safe, short-term intravenous anesthetic for horses, providing stable cardiopulmonary function and a reasonably smooth induction and recovery process.
• However, if the sedative effects of xylazine are not apparent, or if excessive ketamine hydrochloride is used, the combination can lead to serious side effects, negating its use as a horse anesthetic.