Awareness during general anaesthesia--implications of explicit intraoperative recall

Anaesthesia awareness (AA) is postoperative recall of events experienced under general anaesthesia. Most frequently patients remember an auditory perception, the feeling of motor function lost, pain, helplessness, anxiety, panic, impending death. The prevalence of awareness in nonobstetric and noncardiac surgical cases is 0.1%-0.2%. The prevalence is higher in cardiac surgery, obstetric and major trauma cases. According to the results of many studies light anaesthesia is the most common cause of the AA. Posttraumatic stress disorder appears in 33%-56% of patients who experienced awareness during general anaesthesia. Extreme awareness experiences are very uncommon, but traumatic and can have lasting effects on patients. Several brain-function monitors based on the processed electroencephalogram or evoked potentials have been developed to assess anaesthetic depth. Measures to prevent awareness include avoidance of light anesthesia, gaining more knowledge about patient anaesthetic requirements and development of methods to detect consciousness during anesthesia.