Antinociceptive and selected physiological effects of morphine and xylazine on tiletamine-zolazepam anesthesia in llamas

Vet Anaesth Analg. 2014 Jul;41(4):365-71. doi: 10.1111/vaa.12128. Epub 2014 Feb 27.

Abstract

Objective: Evaluate antinociception, anesthesia, and recovery in llamas given tiletamine-zolazepam (TZ) with either morphine, xylazine, morphine and xylazine, or saline.

Study design: Randomized crossover experimental study.

Animals: Six healthy, adult intact male llamas.

Methods: Llamas were given each of four treatments intramuscularly with a 1-week washout: TZ (2 mg kg(-1) ) combined with either morphine (0.5 mg kg(-1) ; M), xylazine (0.15 mg kg(-1) ; X), morphine (0.5 mg kg(-1) ) and xylazine (0.15mg kg(-1) ) (MX), or saline (C). Llamas breathed room air during the experiment. Characteristics of anesthesia, recovery, and selected cardiopulmonary variables were recorded. Antinociception was assessed by clamping a claw at 5-minute intervals. Data were analyzed using a mixed-model anova and Tukey-Kramer test, and are expressed as least squares mean ± SEM. Significance was set at p < 0.05.

Results: No llama in the control group demonstrated antinociception. Antinociception was longest with treatment MX, followed by treatments X and M, respectively. Heart rates in llamas given treatments X and MX were significantly lower than with other treatments. The respiratory rate in llamas given treatment C was greater (p < 0.05) than for all other treatments, however, the respiratory rate was not significantly different among treatments X, M and MX. The PaO2 for llamas given MX remained <60 mmHg throughout the 20 minute period of blood gas analysis. Mean arterial blood pressure in llamas in treatment MX was less than for treatments M or C.

Conclusion and clinical relevance: The combination of morphine (0.5 mg kg(-1) ) and xylazine (0.15 mg kg(-1) ) increased the duration of antinociception compared with xylazine alone, in TZ-anesthetized llamas. Treatments X, M and MX were associated with hypoxemia (PaO2 < 60 mmHg).

Keywords: antinociception; llama; morphine; tiletamine-zolazepam; xylazine.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Anesthesia, Intravenous / veterinary
  • Animals
  • Blood Pressure
  • Camelids, New World*
  • Carbon Dioxide / blood
  • Cross-Over Studies
  • Drug Combinations
  • Heart Rate / drug effects
  • Male
  • Morphine / administration & dosage
  • Morphine / pharmacology*
  • Oxygen / blood
  • Pain / etiology
  • Pain / prevention & control
  • Pain / veterinary*
  • Pressure / adverse effects
  • Tiletamine / administration & dosage
  • Tiletamine / pharmacology*
  • Xylazine / administration & dosage
  • Xylazine / pharmacology*
  • Zolazepam / administration & dosage
  • Zolazepam / pharmacology*

Substances

  • Drug Combinations
  • tiletamine, zolazepam drug combination
  • Carbon Dioxide
  • Xylazine
  • Tiletamine
  • Morphine
  • Zolazepam
  • Oxygen