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

Rachel C. Bennett, Eugene Steffey, Cynthia Kollias-Baker, Richard Sams

Research output: Contribution to journalArticle

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Abstract

Objective - To quantitate the dose and time-related effects of morphine sulfate on the anesthetic sparing effect of xylazine hydrochloride in halothane-anesthetized horses and determine the associated plasma xylazine and morphine concentration-time profiles. Animals - 6 healthy adult horses. Procedure - Horses were anesthetized 3 times to determine the minimum alveolar concentration (MAC) of halothane in O2 and characterize the anesthetic sparing effect (ie, decrease in MAC of halothane) by xylazine (0.5 mg/kg, IV) administration followed immediately by IV administration of saline (0.9% NaCl) solution, low-dose morphine (0.1 mg/kg), or high-dose morphine (0.2 mg/kg). Selected parameters of cardiopulmonary function were also determined over time to verify consistency of conditions. Results - Mean (± SEM) MAC of halothane was 1.05 ± 0.02% and was decreased by 20.1 ± 6.6% at 49 ± 2 minutes following xylazine administration. The amount of MAC reduction in response to xylazine was time dependent. Addition of morphine to xylazine administration did not contribute further to the xylazine-induced decrease in MAC (reductions of 21.9 ± 1.2 and 20.7 ± 1.5% at 43 ± 4 and 40 ± 4 minutes following xylazine-morphine treatments for low- and high-dose morphine, respectively). Overall, cardiovascular and respiratory values varied little among treatments. Kinetic parameters describing plasma concentration-time curves for xylazine were not altered by the concurrent administration of morphine. Conclusions and Clinical Relevance - Administration of xylazine decreases the anesthetic requirement for halothane in horses. Concurrent morphine administration to anesthetized horses does not alter the anesthetic sparing effect of xylazine or its plasma concentration-time profile.

Original languageEnglish (US)
Pages (from-to)519-526
Number of pages8
JournalAmerican Journal of Veterinary Research
Volume65
Issue number4
DOIs
StatePublished - Apr 1 2004

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Xylazine
morphine
xylazine
halothane
Halothane
Morphine
Horses
sulfates
horses
anesthetics
Anesthetics
dosage
intravenous injection

ASJC Scopus subject areas

  • veterinary(all)

Cite this

Influence of morphine sulfate on the halothane sparing effect of xylazine hydrochloride in horses. / Bennett, Rachel C.; Steffey, Eugene; Kollias-Baker, Cynthia; Sams, Richard.

In: American Journal of Veterinary Research, Vol. 65, No. 4, 01.04.2004, p. 519-526.

Research output: Contribution to journalArticle

Bennett, Rachel C. ; Steffey, Eugene ; Kollias-Baker, Cynthia ; Sams, Richard. / Influence of morphine sulfate on the halothane sparing effect of xylazine hydrochloride in horses. In: American Journal of Veterinary Research. 2004 ; Vol. 65, No. 4. pp. 519-526.
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abstract = "Objective - To quantitate the dose and time-related effects of morphine sulfate on the anesthetic sparing effect of xylazine hydrochloride in halothane-anesthetized horses and determine the associated plasma xylazine and morphine concentration-time profiles. Animals - 6 healthy adult horses. Procedure - Horses were anesthetized 3 times to determine the minimum alveolar concentration (MAC) of halothane in O2 and characterize the anesthetic sparing effect (ie, decrease in MAC of halothane) by xylazine (0.5 mg/kg, IV) administration followed immediately by IV administration of saline (0.9{\%} NaCl) solution, low-dose morphine (0.1 mg/kg), or high-dose morphine (0.2 mg/kg). Selected parameters of cardiopulmonary function were also determined over time to verify consistency of conditions. Results - Mean (± SEM) MAC of halothane was 1.05 ± 0.02{\%} and was decreased by 20.1 ± 6.6{\%} at 49 ± 2 minutes following xylazine administration. The amount of MAC reduction in response to xylazine was time dependent. Addition of morphine to xylazine administration did not contribute further to the xylazine-induced decrease in MAC (reductions of 21.9 ± 1.2 and 20.7 ± 1.5{\%} at 43 ± 4 and 40 ± 4 minutes following xylazine-morphine treatments for low- and high-dose morphine, respectively). Overall, cardiovascular and respiratory values varied little among treatments. Kinetic parameters describing plasma concentration-time curves for xylazine were not altered by the concurrent administration of morphine. Conclusions and Clinical Relevance - Administration of xylazine decreases the anesthetic requirement for halothane in horses. Concurrent morphine administration to anesthetized horses does not alter the anesthetic sparing effect of xylazine or its plasma concentration-time profile.",
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N2 - Objective - To quantitate the dose and time-related effects of morphine sulfate on the anesthetic sparing effect of xylazine hydrochloride in halothane-anesthetized horses and determine the associated plasma xylazine and morphine concentration-time profiles. Animals - 6 healthy adult horses. Procedure - Horses were anesthetized 3 times to determine the minimum alveolar concentration (MAC) of halothane in O2 and characterize the anesthetic sparing effect (ie, decrease in MAC of halothane) by xylazine (0.5 mg/kg, IV) administration followed immediately by IV administration of saline (0.9% NaCl) solution, low-dose morphine (0.1 mg/kg), or high-dose morphine (0.2 mg/kg). Selected parameters of cardiopulmonary function were also determined over time to verify consistency of conditions. Results - Mean (± SEM) MAC of halothane was 1.05 ± 0.02% and was decreased by 20.1 ± 6.6% at 49 ± 2 minutes following xylazine administration. The amount of MAC reduction in response to xylazine was time dependent. Addition of morphine to xylazine administration did not contribute further to the xylazine-induced decrease in MAC (reductions of 21.9 ± 1.2 and 20.7 ± 1.5% at 43 ± 4 and 40 ± 4 minutes following xylazine-morphine treatments for low- and high-dose morphine, respectively). Overall, cardiovascular and respiratory values varied little among treatments. Kinetic parameters describing plasma concentration-time curves for xylazine were not altered by the concurrent administration of morphine. Conclusions and Clinical Relevance - Administration of xylazine decreases the anesthetic requirement for halothane in horses. Concurrent morphine administration to anesthetized horses does not alter the anesthetic sparing effect of xylazine or its plasma concentration-time profile.

AB - Objective - To quantitate the dose and time-related effects of morphine sulfate on the anesthetic sparing effect of xylazine hydrochloride in halothane-anesthetized horses and determine the associated plasma xylazine and morphine concentration-time profiles. Animals - 6 healthy adult horses. Procedure - Horses were anesthetized 3 times to determine the minimum alveolar concentration (MAC) of halothane in O2 and characterize the anesthetic sparing effect (ie, decrease in MAC of halothane) by xylazine (0.5 mg/kg, IV) administration followed immediately by IV administration of saline (0.9% NaCl) solution, low-dose morphine (0.1 mg/kg), or high-dose morphine (0.2 mg/kg). Selected parameters of cardiopulmonary function were also determined over time to verify consistency of conditions. Results - Mean (± SEM) MAC of halothane was 1.05 ± 0.02% and was decreased by 20.1 ± 6.6% at 49 ± 2 minutes following xylazine administration. The amount of MAC reduction in response to xylazine was time dependent. Addition of morphine to xylazine administration did not contribute further to the xylazine-induced decrease in MAC (reductions of 21.9 ± 1.2 and 20.7 ± 1.5% at 43 ± 4 and 40 ± 4 minutes following xylazine-morphine treatments for low- and high-dose morphine, respectively). Overall, cardiovascular and respiratory values varied little among treatments. Kinetic parameters describing plasma concentration-time curves for xylazine were not altered by the concurrent administration of morphine. Conclusions and Clinical Relevance - Administration of xylazine decreases the anesthetic requirement for halothane in horses. Concurrent morphine administration to anesthetized horses does not alter the anesthetic sparing effect of xylazine or its plasma concentration-time profile.

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