Recall during intermittent propofol anaesthesia

We discontinued temporarily an infusion of propofol for surgical reasons in 20 patients undergoing incontinence surgery. The patients, who had not received neuromuscular blockers, were allowed to regain consciousness to a level enabling them to cough on command, open their eyes, and identify and verbally confirm a randomly assigned digit shown on paper. Thereafter, 5-14 min after discontinuation of the propofol infusion, anaesthesia was reinstituted. Memory of the request to cough, a standard conversation and the digit shown was tested 1 h after anaesthesia and on the following day. Only 35% of patients were able to recall one or more of the stimuli presented during wakefulness or were even able to recall having been "awake", and there were very few differences in memory on the day after surgery compared with 1 h after anaesthesia. In comparison with corresponding stimuli given before anaesthesia, memory of material learned during wakefulness was significantly impaired (P < 0.0001). Thus patients temporarily capable of cognitive action during propofol anaesthesia may have no subsequent explicit recall of intraoperative events.