Anaesthesia, awareness and automation

Awareness in anaesthesia: incidence, consequences and prevention

Awareness during anaesthesia is a state of consciousness that is revealed by explicit or implicit memory of intraoperative events. Although large clinical surveys indicate an incidence of explicit awareness of < 0.3% during anaesthesia for general surgery, this adverse effect should be a great concern, because patients may be permanently disabled by the experience of being awake during surgery. Prevention of awareness during anaesthesia starts with an appropriate preoperative visit to the patient. The anaesthetic delivery machines must be properly checked before and during anaesthesia. The anaesthetic depth should be assessed by observation of movement responses, and consequently a minimum of muscle relaxants used. Because the anaesthetic depth can be controlled by determination of endtidal drug concentration, volatile inhaled anaesthesia may be associated with a lower frequency of awareness than other anaesthetic regimens.

Total intravenous anaesthesia

Total intravenous anaesthesia is a feasible alternative to the use of inhalational agents and the rationale behind such a technique is presented. The various intravenous agents are discussed, particularly with regard to their suitability for this form of anaesthesia, and their physiological effects compared with those of the inhalational anaesthetics. Some of the problems associated with the use of total intravenous anaesthesia are mentioned.