Absence of memory for intraoperative information during surgery under adequate general anaesthesia

Using the isolated forearm technique (IFT), we wished to determine if patients known to be unresponsive to commands during general anaesthesia with nitrous oxide, halothane and neuromuscular blocking agents had any evidence of explicit or implicit recall. Two groups of women, studied in a single-blind sequential block design, heard different tapes, either a command and information tape (n = 34) or radio static (n = 34), throughout surgery. Four women (two radio static, two command) had unequivocal evidence of explicit recall for a period near the beginning or end of the procedure, at a time when the IFT was not being used. With or without hypnosis, category generation, serial position of category exemplars and word association tests did not reveal evidence of priming. We conclude that during light general anaesthesia with nitrous oxide, halothane and atracurium, patients had neither explicit nor implicit memory for information presented during a period when they are known to be unresponsive to commands.