Development of a xylazine constant rate infusion with or without butorphanol for standing sedation of horses
Article first published online: 22 NOV 2011
© 2011 The Authors. Veterinary Anaesthesia and Analgesia. © 2011 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists
Veterinary Anaesthesia and Analgesia
Volume 39, Issue 1, pages 1–11, January 2012
How to Cite
Ringer, S. K., Portier, K. G., Fourel, I. and Bettschart-Wolfensberger, R. (2012), Development of a xylazine constant rate infusion with or without butorphanol for standing sedation of horses. Veterinary Anaesthesia and Analgesia, 39: 1–11. doi: 10.1111/j.1467-2995.2011.00653.x
- Issue published online: 12 DEC 2011
- Article first published online: 22 NOV 2011
- Received 22 July 2010; accepted 6 September 2010.
- constant rate infusion;
Objective To elaborate constant rate infusion (CRI) protocols for xylazine (X) and xylazine/butorphanol (XB) which will result in constant sedation and steady xylazine plasma concentrations.
Study design Blinded randomized experimental study.
Animals Ten adult research horses.
Methods Part I: After normal height of head above ground (HHAG = 100%) was determined, a loading dose of xylazine (1 mg kg−1) with butorphanol (XB: 18 μg kg−1) or saline (X: equal volume) was given slowly intravenously (IV). Immediately afterwards, a CRI of butorphanol (XB: 25 μg kg−1 hour−1) or saline (X) was administered for 2 hours. The HHAG was used as a marker of depth of sedation. Sedation was maintained for 2 hours by additional boluses of xylazine (0.3 mg kg−1) whenever HHAG >50%. The dose of xylazine (mg kg−1 hour−1) required to maintain sedation was calculated for both groups. Part II: After the initial loading dose, the calculated xylazine infusion rates were administered in parallel to butorphanol (XB) or saline (X) and sedation evaluated. Xylazine plasma concentrations were measured by HPLC-MS-MS at time points 0, 5, 30, 45, 60, 90, and 120 minutes. Data were analyzed using paired t-test, Wilcoxon signed rank test and a 2-way anova for repeated measures (p < 0.05).
Results There was no significant difference in xylazine requirements (X: 0.69, XB: 0.65 mg kg−1 hour−1) between groups. With treatment X, a CRI leading to prolonged sedation was developed. With XB, five horses (part I: two, part II: three) fell down and during part II four horses appeared insufficiently sedated. Xylazine plasma concentrations were constant after 45 minutes in both groups.
Conclusion Xylazine bolus, followed by CRI, provided constant sedation. Additional butorphanol was ineffective in reducing xylazine requirements and increased ataxia and apparent early recovery from sedation in unstimulated horses.
Clinical relevance Data were obtained on unstimulated healthy horses and extrapolation to clinical conditions requires caution.