Awareness during general anaesthesia

A patient does not expect to be aware of any kind of sensory sensation during general anaesthesia and to remember it afterwards. Intraoperative awareness is present, when the patient, at least in part, perceives sensory input or actively responds to a command while under general anaesthesia. The diagnosis of awareness is verified postoperatively on the basis of a structured interview. The incidence of awareness with explicit memory is 1-2 parts per thousand in adults, and up to about 1 % in children (5-18 years) and high-risk patients. Intra-operative awareness may later cause posttraumatic stress disorder in the individual patient. Potential patient-related risk factors for intraoperative awareness are: drug abuse or addiction, difficult intubation, a history of chronic pain or opioid treatment, ASA-classification IV-V, reduced cardiovascular reserve, and an earlier experience of intra-operative awareness. Surgery- or anaesthesia-related factors include emergency operation, caesarean section, cardiac or trauma surgery, muscle relaxant use during the maintenance phase, night-time surgery, non use of benzodiazepine premedication, and total intravenous anaesthesia. During anaesthesia, monitoring of the end-tidal concentration of volatile anaesthetics, careful management by the anaesthesiologist or the monitoring of the depth of anaesthesia might help to avoid awareness. If a patient experiences awareness, appropriate support in the immediate postoperative period is necessary. Should a patient develop symptoms indicative of a posttraumatic stress disorder, psychological or psychiatric help should be initiated.