Awareness with recall during general anaesthesia:: a prospective observational evaluation of 4001 patients

Background. We have prospectively evaluated the incidence and characteristics of awareness with recall (AWR) during general anaesthesia in a tertiary care hospital. Methods. This study involves a prospective observational investigation of AWR in patients undergoing general anaesthesia. Blinded structured interviews were conducted in the postanaesthesia care unit, on postoperative day 7 and day 30. Definition of AWR was 'when the patient stated or remembered that he or she had been awake at a time when consciousness was not intended'. Patient characteristics, perioperative, and drug-related factors were investigated. Patients were classified as not awake during surgery, AWR, AWR-possible, AWR-not evaluable. The perceived quality of the awareness episode, intraoperative dreaming, and sequelae were investigated. The anaesthetic records were reviewed to search for data that might explain the awareness episode. Results. The study included 4001 patients. Incidence of AWR was 1.0% (39/3921 patients). If high risk for AWR patients were excluded, the incidence was 0.8%. After the interview on the seventh day, six patients denied having been conscious during anaesthesia; hence, the incidence of AWR in elective surgery was 0.6%. Factors associated with AWR were: anaesthetic technique incidence of 1.1% TIVA-propofol vs 0.59% balanced anaesthesia vs 5.0% O-2/N2O-based anaesthesia vs 0.9% other anaesthetic techniques (mainly propofol boluses for short procedures), P=0.008; age (AWR 42.3 yr old vs 50.6 yr old, P=0.041), absence of i.v. benzodiazepine premedication (P=0.001), Caesarean section (C-section) (P=0.019), and surgery performed at night (P=0.013). More than 50% of patients reported intraoperative dreaming in the early interview, mainly pleasant. Avoidable human factors were detected from the anaesthetic records of most patients. Subjective auditory perceptions prevailed, together with trying to move or communicate, and touch or pain perception. Conclusions. A relatively high incidence of AWR and dreams during general anaesthesia was found. Techniques without halogenated drugs showed more patients. The use of benzodiazepine premedication was associated with a lower incidence of AWR. Age, C-section with general anaesthesia, and surgery performed at night are risk factors.