Effects of xylazine hydrochloride during isoflurane-induced anesthesia in horses.
OBJECTIVE
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.


METHODS
6 healthy adult horses.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Steffey
E P
EP
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis 95616, USA.
Pascoe
P J
PJ
Woliner
M J
MJ
Berryman
E R
ER
D018685:Anesthetics, Inhalation / Q000008:administration & dosage; D000818:Animals; D001784:Blood Gas Analysis; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004347:Drug Interactions; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000378:metabolism*; D007530:Isoflurane / Q000008:administration & dosage; D008297:Male; D011650:Pulmonary Alveoli / Q000378:metabolism; D014991:Xylazine / Q000008:administration & dosage / Q000494:pharmacology*
D018685:Anesthetics, Inhalation; D001786:Blood Glucose; D014991:Xylazine; D007530:Isoflurane