Effects of propofol administration rates on cardiopulmonary function and anaesthetic depth during anaesthetic induction in rats.

OBJECTIVE To compare the effect of three different administration rates of one dose of propofol on the depth and duration of anaesthesia and cardiopulmonary function during induction of anaesthesia in rats using electroencephalogram (EEG) and clinical signs. STUDY DESIGN Prospective, randomized experimental trial. Animals Twenty-one, adult, male Sprague-Dawley rats weighing 341 +/- 26 g (mean +/- SD) (325 to 480 g). METHODS ANIMALS were randomly divided into three groups to receive 20 mg kg(-1) propofol as a bolus injection over 1, 2 or 3 minutes (groups P1, P2 and P3 respectively) intravenously (IV). The total duration and number of burst suppression (BS) episodes in the EEG, the time to loss of righting reflex, reflex score from electrical stimulation, respiratory rate, mean arterial pressure and pulse rate were measured from the beginning of propofol injection. RESULTS While loss of reflex to electrical stimulus and time to loss of righting reflex in group P3 were slower than in other groups, the total duration and number of BS episodes in group P3 were significantly higher than in groups P1 and P2 and cardiopulmonary depression was less prominent in group P3 than in groups P1 and P2 up to 2 minutes after the start of administration. CONCLUSIONS Twenty milligram per kg propofol administration IV for 3 minutes increased the duration of anaesthesia and decreased cardiopulmonary depression in rats. CLINICAL RELEVANCE Slower infusion of propofol produced surgical anaesthesia with less cardiopulmonary depression in rats.