Review of Procedures for Investigation of Anaesthesia-Associated Anaphylaxis in Newcastle, Australia

The procedures, results and outcomes of investigation of 50 patients with clinical episodes of anaesthesia-associated anaphylaxis were retrospectively reviewed. Assessment was performed by measurement of serum tryptase and specific IgE and a combination of skin prick and intradermal skin testing. Testing was performed both for agents received during the anaesthetic and for agents the patient may encounter in future procedures. Twenty of 50 patients underwent a subsequent procedure after assessment. Sensitisation to neuromuscular blocking agents was identified in 18 patients (36%). Sensitisation to propofol (14 patients; 28%) and latex (four patients; 8%) was also frequently identified. No precise cause was identified in 11 cases (22%). Reactivity to more than one agent was identified in 14 patients (28%). Serum tryptase was measured within six hours of the episode in only 28 of the 50 cases. All the patients with elevated serum tryptase had clinically severe reactions. One patient initially found to be sensitised to propofol had another reaction during a second procedure, prompting further assessment where chlorhexidine reactivity was identified. Subsequent surgery in that patient and in 19 other patients where agents implicated in the testing were avoided, proceeded without incident. The results reaffirm that neuromuscular blocking agents are the most common cause of anaphylaxis during anaesthesia. The importance of serum tryptase measurement at the time of the acute episode needs to be emphasised. Investigation should include screening for chlorhexidine and latex in all patients, as exposure to both these agents is common and may be overlooked.