9 Anaphylactic and anaphylactoid reactions

Anaphylaxis is a rare event during anaesthesia but may lead to death, even when expertly treated. Reactions may be immune related (anaphylactic) or as a result of direct stimulation (anaphylactoid). The clinical features result from massive release of histamine and the release of other mediators. There is a wide spectrum of severity of reaction but the mainstay of treatment is adrenaline, intravenous colloid and 100% oxygen. Investigation is important, enabling identification of the agent and other agents potentially causing life-threatening reactions. Mast cell tryptase is measured in the first 6 hours, to identify the reaction as anaphylactic, and skin testing 4–6 weeks later is best at identifying the trigger agent. Giving the patient full documentation of the reaction and investigations along with an explanation of the seriousness of the situation is imperative.