SUMMARY

The original classification of adverse drug reac-tions into Type A (exaggerated but otherwise normal pharmacological response), and Type B (unusual pharmacological response) [1] is irrele-vant to the rapid onset reactions encountered during induction of anaesthesia. The most hazar-dous situation encountered by the anaesthetist is the immediate hypersensitivity response. These reactions, which unfortunately seem to be increas-ing in number annually [2,3], are largely unpre-dictable. The reaction, which is manifest anaphyl-axis, is described best as anaphylactoid pending investigation of the aetiology, and corresponds to Type B reactions of the older classification. Anaphylactoid reactions to i.v. anaesthetic agents range from skin rashes to an overpowering systemic response causing bronchospasm, hypo-tension and cardiac arrest. Several mechanisms may operate in these anaphylactoid reactions which lead ultimately to an adverse clinical response [4,5]. The importance of obtaining a history of allergy from the patient or relatives during the preoperative assessment has been emphasized by others [6,7]. However, reviews of anaphylactoid reactions to thiopentone suggest that 80 % occur without prior exposure, and do not involve antibodies of any type [2]. A moderately obese and anxious 63-yr-old female presented for ulnar nerve release under general anaesthesia. Her past history revealed two previous general anaesthetics, 16 and 3 yr before this event. After premedication with papaveretum 15 mg and prochlorperazine 12.5 mg, anaesthesi