Etomidate: an 'immunologically safe' anaesthetic agent.

A review of the important aspects of immunity and its disturbance by drugs is given, together with a resumé of the various immunological pathways involved in adverse anaesthetic reactions. Etomidate is unique amongst anaesthetic drugs in that it does not release plasma histamine. Between 1978 and 1982, five cases of possible reactions involving the use of etomidate were investigated. All involved only immediate widespread cutaneous flushing or urticaria, which was followed in two cases by extensive perioperative vomiting. The direct involvement of etomidate was uncertain. In 1982 two further cases were investigated which also involved hypotension. In both, suxamethonium and/or alcuronium had been used. The first case was repeated uneventfully when etomidate was used with pancuronium. The second case is as yet unresolved but the reaction was again probably caused by the muscle relaxants. The absence of severe reactions, and particularly cardiovascular effects, to etomidate leads the author to recommend its use in high risk patients, such as those with allergy or atopy and in those who have previously exhibited severe anaphylactoid responses.