The effect of propofol on patient reaction time and its relationship with loss of verbal contact before induction of anaesthesia.

Abstract

Increasing the calculated plasma concentration of propofol has been shown to increase choice reaction time and visual and auditory response times. We studied the relationship of reaction to a vibrating handset as the effect-site target-controlled propofol concentration was incrementally increased in 20 patients during sedation, before induction of general anaesthesia. The reaction time increased, initially slowly and then more rapidly, as the calculated effect-site concentration of propofol increased, until the reaction to the vibrating handset was lost at a mean (SD) propofol effect-site concentration of 2.0 (0.6) μg.ml(-1) . The loss of response to verbal contact occurred at a propofol effect-site concentration of 2.4 (0.5) μg.ml(-1) . Reaction time may be of use clinically to warn of impending loss of verbal contact.