Optimum rate of administration of propofol for induction of anaesthesia in rats.

Twenty rats received propofol 2.5, 5, 10 or 20 mg kg-1 min-1 i.v. Brain activity was monitored using the electroencephalogram (EEG). As the endpoint for induction of anaesthesia we used a burst suppression period of 1 s or longer. At a fast (20 mg kg-1 min-1) rate of administration, the induction dose was significantly larger compared with a slower rate (10 mg kg-1 min-1). At a slow rate of administration (2.5 mg kg-1 min-1), the induction dose was also significantly larger compared with a rate of 10 mg kg-1 min-1. In spite of different dose requirements at different rates of administration, duration of anaesthesia was not significantly different.