Absence of memory for intraoperative information

Abstract

Their study seemed to have been motivated by their belief that the brain can only process information during anaesthesia if anaesthesia is inadequate enough to result in the patient being conscious. Using the isolated forearm technique (IFT), they showed that there was no evidence for explicit recall, or implicit memory changes in patients, for times at which these patients were unresponsive to verbal command. I would agree that changes in implicit memory are more likely to occur at times when the anaesthetized patient is responsive to verbal command, but their assumption that an observed response when using the IFT automatically indicates a state of consciousness is, I believe, not warranted. As they themselves quoted, with some general anaesthetic tech- niques more than 70% of patients may be capable of responding to commands during surgery (using IFT), with no postoperative explicit recall of intraoperative events. It is still not necessarily the case however, that the patient was conscious, even if postoperative changes in implicit memory are demonstrated in these patients. All this implies is that the brain has processed information in some way and created a response. The authors seem to believe that IFT acts as a reliable “consciousness monitor” or indicator of “adequate” anaesthesia, but they disregard the possibility that responses observed while using this technique might also reflect pre-conscious information porcenssig .nI ohte wrodsr w,heeras peanits tmgih terspond appropriately, they might still not be conscious. The major fault with this study is that in attempting to disprove the notion of pre-conscious information processing, they make use of a clinical tool (IFT) which, much of the time, may in fact measure exactly what they wish to disprove. U lniwthen ,and i i ,t desfi moneard tttsh ath tstiype o fanaesthesia results in significant psychological morbidity, there is no reason to suppose that it is not “adequate”. M. B. H