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‘Two cautionary tales’

The letter ‘Follow-up of reported awareness’ (Anaesthesia 1993; 48: 927) is of interest because it reports a case of alleged awareness in a patient whose lungs were ventilated with 1% isoflurane in 65% nitrous oxide. Investigation of such a case should surely be directed towards establishing whether the conversations the patient recalled really did take place during the course of the operation. The content of the conversation, particularly whether they were related to the patient or her condition, may be of importance as is the nature of the operation. If the conversation was correctly recalled the next step should be to verify that the patient’s lungs really were ventilated continuously with a gas mixture of the composition stated. If it can be shown that recall can take place even during ventilation with an anaesthetic gas mixture having a total MAC of about 150% then this has considerable implications for routine clinical practice.