Although anaesthesia is safer than in the past, complications do occur. One large study showed that about 10 per cent of patients experienced some problem during or after the anaesthetic. The complication could be as major as brain damage (but extremely rare) or as minor as muscle soreness (but more common). The most frequent complications are nausea, vomiting and sore throat. Anaesthetists are trained to recognise and manage complications quickly, and many will undergo part of this emergency training in simulators, much like airline pilots do.

The accompanying lists describe some of the complications that may occur during or after an anaesthetic. This lists are selective and do not include all complications.