Failure to demonstrate unconscious perception during balanced anaesthesia by postoperative motor response.

Eighty patients undergoing a standardized balanced anaesthesia were randomly assigned to either a suggestion group (N = 38) or a control group (N = 42), in a double-blind design. Anaesthesia was maintained with nitrous oxide, enflurane and fentanyl. Patients in the suggestion group were played seaside sounds, interrupted by statements of the importance of touching the ear during a postoperative visit, by means of a prerecorded audiotape and headphones. Tapes containing these suggestions were played from 30 min after the first incision, for a duration of 15 min. Patients in the control group were only played seaside sounds. There were no significant differences between the groups in either the number of patients touching their ears postoperatively or the number and duration of ear touches.