XYLAZINE OR MEDETOMIDINE PREMEDICATION BEFORE PROPOFOL ANESTHESIA

The duration of action and cardiopulmonary effects of propofol (6.55 m g/kg intravenously), xylazine (0.8 mg/kg intramuscularly), medetomidin e (30 mug/kg intramuscularly), xylazine plus propofol (3 mg/kg intrave nously) and medetomidine plus propofol (3 mg/kg intravenously) were co mpared in dogs. A cannula inserted into a raised carotid artery before the drugs were given allowed the continuous recording of blood pressu re and heart rate and the measurement of arterial pH, P(CO2), P(O2), b icarbonate and base balance. Xylazine and medetomidine premedication p rolonged propofol anaesthesia in dogs. Propofol alone reduced blood pr essure and transiently raised heart rate. The apnoea and hypoxaemia in duced by propofol alone also occurred in the premedicated groups with hypoxaemia being most evident in the medetomidine/propofol group. Brad ycardia was a common feature in all the dogs given xylazine or medetom idine, but hypertension was consistently recorded in all the dogs give n medetomidine.