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

Seddighi, Reza, Elliot, Sarah B, Whitlock, Brian K, Egger, Christine M, Doherty, Thomas J
Veterinary anaesthesia and analgesia 2014 v.41 no.4 pp. 365-371
adults, anesthesia, blood gases, blood pressure, experimental design, heart, hypoxia, least squares, llamas, morphine, respiratory rate, xylazine
Evaluate antinociception, anesthesia, and recovery in llamas given tiletamine-zolazepam (TZ) with either morphine, xylazine, morphine and xylazine, or saline.Randomized crossover experimental study.Six healthy, adult intact male llamas.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.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.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).