Behavioral and Cardiopulmonary Effects of a Constant Rate Infusion of Remifentanil-Xylazine for Sedation in Horses.

The research explores the effect of using a continuous rate infusion of remifentanil and xylazine for sedating horses, and it demonstrates that this method has no adverse effects.

Objective of the Research

• To assess the impact of continuous rate infusion of remifentanil and xylazine on a horse’s behavior and cardiopulmonary performance.

Methodology

• Ten healthy horses were used in the study.
• Each was given a dose of xylazine (0.8 mg/kg intravenously), followed three minutes later by a continuous infusion of both xylazine and remifentanil (0.65 mg/kg/hr and 6 μg/kg/hr respectively) for a duration of 60 minutes.
• Various factors such as the horses’ sedation, balance control (ataxia), cardiopulmonary functionality, and blood variables were observed and measured during this process.

Observations

• The horse’s heart rate decreased significantly in the first 25 minutes after the continuous infusion of xylazine and remifentanil.
• Respiratory rate decreased significantly at the 20-minute mark and sustained this lower rate until the end of the experiment.
• No significant variations were recorded for blood arterial pressure, blood pH, arterial carbon dioxide partial pressure, lactate, creatinine, calcium, chlorine, and sodium, when compared to initial baseline values.
• Arterial oxygen and bicarbonate blood partial pressures were noticeably higher in comparison with baseline values, whereas potassium levels decreased.
• Sedation and loss of balance (ataxia) were immediately noticeable following the xylazine administration in all of the horses, however, this was not permanent.
• All horses successfully recovered within 10 minutes of the continuous infusion cessation, displaying no ataxia. No adverse effects were visible.

Conclusion

• The study concluded that a combination of xylazine and remifentanil, when used as a sedative measure for horses and administered at described dosages, shows no adverse outcomes.