Induction of anaesthesia with propofol using a target‐controlled infusion system

Sixty patients premedicated with temazepam were allocated randomly to receive an infusion of propofol designed to achieve and maintain a target blood concentration of 3, 4 or 5 micrograms.ml-1. Induction time was measured from the start of infusion to loss of verbal contact. The success rate of inducing anaesthesia within 3 min of achieving the target concentration was 40% when the predicted target concentration was 3 micrograms.ml-1, 75% when the predicted target was 4 micrograms.ml-1 and 90% when the target was 5 micrograms.ml-1. There were no significant differences between the three groups for time to loss of verbal contact in patients who were induced successfully within 3 min. There were significant reductions in arterial pressure 3 min after achieving the target concentrations within the groups but not between them. The frequency of apnoea and pain on injection was small in all groups. Selecting a target concentration of 5 microgram.ml-1 would successfully induce anaesthesia in the majority of patients premedicated with temazepam without major haemodynamic or respiratory side effects.