Influence of morphine sulfate on the halothane sparing effect of xylazine hydrochloride in horses.

The research shows how morphine sulfate impacts the decreasing effect of xylazine hydrochloride on the requirement for halothane anesthesia in horses. The study found out that while xylazine lessens the need for halothane, the addition of morphine does not significantly affect this reduction.

Research Methods

• Six healthy adult horses were used in the research.
• The horses were anesthetized three times. The process was to determine the minimum alveolar concentration (MAC) of halothane in oxygen and characterize the anesthetic sparing effect. This effect refers to the decrease in the MAC of halothane triggered by xylazine administration.
• The dosage of xylazine was 0.5 mg/kg and was administered intravenously.
• The administration of xylazine was immediately followed by the intravenous administration of either saline solution (0.9% NaCI), a low dose of morphine (0.1 mg/kg), or a high dose of morphine (0.2 mg/kg).
• Specific parameters of cardiopulmonary function were also determined over time to ensure the consistency of conditions.

Research Findings

• The mean MAC of halothane was established to be 1.05 +/- 0.02%, which decreased by 20.1 +/- 6.6% at approximately 49 minutes following the administration of xylazine. The reduction in MAC after administering xylazine was found to be dependent on time.
• When morphine was added to xylazine administration, it did not significantly contribute to the xylazine-induced decrease in MAC. Whether low- or high-dose morphine was used, the reductions were 21.9 +/- 1.2 and 20.7 +/- 1.5% at 43 +/- 4 and 40 +/- 4 minutes, respectively, after administering the xylazine-morphine combination.
• Cardiovascular and respiratory values changed very little among treatments.
• Simultaneous morphine administration did not alter the kinetic parameters describing plasma concentration-time curves for xylazine.

Conclusion

• Administering xylazine decreases the anesthetic requirement for halothane in horses.
• The administration of morphine in conjunction with anesthesia does not significantly alter the anesthetic sparing effect of xylazine or its plasma concentration-time profile.