Patient-maintained propofol sedation as premedication in day-case surgery: assessment of a target-controlled system

We have assessed the efficacy and safety of a system which allowed 20 patients undergoing day-case anaesthesia to operate a target-controlled infusion of propofol to provide anxiolytic premedication. A target-controlled infusion of propofol was started with a target blood concentration of 1 microgram ml-1, and the patient was allowed to increase the target by 0.2 microgram ml-1 by operating a control button. There was a lockout time of 2 min and a maximum target concentration of 3 micrograms ml-1. There were significant reductions in anxiety scores from presedation baseline values and those measured at 15 min after the start of sedation. Values remained low until induction of anaesthesia. Median blood target concentration of propofol varied from 1.0 to 1.2 micrograms ml-1 and mean propofol consumption was 50.3 (SD 17.6) micrograms kg-1 min-1. No patient became oversedated and all remained cardiovascularly stable. Two individuals required low-dose supplementary oxygen for mild arterial oxygen desaturation but there were no instances of airway obstruction. Patient satisfaction with the system was high.