Cardiovascular and haemodynamic effects of intramuscular doses of xylazinein conscious sheep

Objective To determine if a commonly used analgesic dose of xylazine has de trimental cardiovascular or haemodynamic effects in sheep. Design A physiological study following intramuscular administration of xyla zine. Procedure Xylazine (50 mug/kg) was injected intramuscularly into six health y Merino ewes. For 60 min heart rate, mean arterial blood pressure and card iac output were recorded; arterial blood samples for the measurement of blo od gas tensions were also collected. Results There were no significant changes in heart rate, mean arterial bloo d pressure, cardiac output or arterial carbon dioxide tension. A slight deg ree of arterial hypoxaemia was noted with a 10% reduction in arterial oxyge n tension values at 30 min. Conclusion The minimal changes to cardiovascular and respiratory values in this study verify the safety of previously suggested analgesic dosing regim ens for sheep. Previously reported hypoxaemic effects in sheep as a result of intravenous xylazine administration appear to be reduced as a result of intramuscular administration.