Memory for auditory material presented during anaesthesia

We have assessed postoperative memory for lists of 10 neutral words, presented by tape recording, in patients anaesthetized by a standardized technique comprising thiopentone 5 mg kg-1, midazolam 0.07 mg kg-1, fentanyl 3 micrograms kg-1 and 70% nitrous oxide in oxygen, using both free recall and a test in which the subject was asked to indicate the presented words from a larger list. Twenty-four patients were exposed to one of four tape-recorded lists of words and 24 were presented with a blank tape. There was no instance of free recall of presented words. Analysis of the responses in the implicit memory test revealed no difference between the performance of the patients who had been exposed to a word list and those who had not.