Effects of xylazine hydrochloride during isoflurane-induced anesthesia in horses

• Published in: American journal of veterinary research Vol. 61; no. 10; pp. 1225 - 1231
• Main Authors: Steffey, E P, Pascoe, P J, Woliner, M J, Berryman, E R
• Format: Journal Article
• Language: English
• Published: United States 01-10-2000
• Subjects: Anesthetics, Inhalation - administration & dosage; Animals; Blood Gas Analysis; Blood Glucose - metabolism; Blood Pressure - drug effects; Dose-Response Relationship, Drug; Drug Administration Schedule; Drug Interactions; Female; Heart Rate - drug effects; Horses - metabolism; Isoflurane - administration & dosage; Male; Pulmonary Alveoli - metabolism; Xylazine - administration & dosage; Xylazine - pharmacology
• ISSN: 0002-9645
• DOI: 10.2460/ajvr.2000.61.1225

To quantitate dose- and time-related anesthetic-sparing effects of xylazine hydrochloride (XYL) during isoflurane-induced anesthesia in horses and to characterize selected physiologic responses of anesthetized horses to administration of XYL.
6 healthy adult horses.
Horses were anesthetized 2 times to determine the minimum alveolar concentration (MAC) of isoflurane in O2 and to characterize the anesthetic-sparing effect (MAC reduction) after IV administration of XYL (0.5 and 1 mg/kg of body weight, random order). Selected measures of cardiopulmonary function, blood glucose concentrations, and urinary output also were measured during the anesthetic studies.
Isoflurane MAC (mean +/- SEM) was reduced by 24.8 +/- 0.5 and 34.2 +/- 1.9% at 42 +/- 7 and 67 +/- 10 minutes, respectively, after administration of XYL at 0.5 and 1 mg/kg. Amount of MAC reduction by XYL was dose- and time-dependent. Overall, cardiovascular and respiratory values varied little among treatments. Administration of XYL increased blood glucose concentration; the magnitude of change was dose- and time-dependent. Urine volume increased but not significantly.
Administration of XYL reduced the anesthetic requirement for isoflurane in horses. The magnitude of the decrease is dose- and time-dependent. Administration of XYL increases blood glucose concentration in anesthetized horses in a dose-related manner.