647 The diagnosis of anaphylactic reactions to muscle relaxants by flow cytometry

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645 A L L E R G I C R E A C T I O N S D U R I N G G E N E R A L A N E S T H E S I A (GA) . SR K n o w l e s BScPhm, E Weber , MD, NH Shear, MD. Toronto , Ontario. "Allergic" reactions to intravenous agents used during GA occur in approximately 1 in 6000 operations. Although the mechanism may be either immunologic or non-immunologic, a number of studies have shown the usefulness of skin testing to confirm allergy to muscle relaxants, barbiturates and latex. In order to investigate patients who presentod to the ADR Clinic for evaluation of allergic-type reactions occurring during GA, a battery of standardized skin tests using nonirritant concentrations of implicated drugs and latex was done. 15 patients (12 F/3 M, average age 44 +18 years) with allergic-type reactions during GA (5 systemic, 5 isolated hypotension, 4 urticaria/angioedema, I vomiting) were investigated. 4 patients hadno docnmentationof previous anesthesia, 9 patients had a reaction in a previous course, and in 2 patients it was unknown whether or not they had undergone prior surgery. There a clear history of atopy in 3 patients. Positive skin test results were obtained in 8/15 (53%) patients. Prick tests in 3 patients were positive using thiopental and in one of these patients, latex skin tests were also positive. Intradermal testing was positive in 5 patients (2 tubocurarine. 1 suecinylcholine, l atracudum, I thiopental). Of the 4 patients who tested positive with a muscle relaxant, 3 patients had no history of surgery. Reactions during surgery have been documented to occur more frequently in females. Although the female/male ratio in our study was 4: l, this may simply reflect a referral bias seen in the ADR Clinic. A history of atopy does not appear to be a risk factor for reactions during GA in our patients. Therefore, skin testing with agents used during GA aids in the identification of a drug that may have precipitated the anaphylactie reaction in about half of patients and can be used to guide future chug selection. 647 The Diagnosis of Anaphylactic Reactions to Muscle Relaxants by Flow Cytometry. F Lcynadier MD. B Raiocly MD, E Ghazouani MD, H Firat. C Pecouet MD. N A b u a f MD, Paris, FRANCE. The skin tests remain the gold standard for defining muscle relaxants drugs allergy after anaphylactie reactions. In vitro testing by R A S T is general ly less reliable. We have previously reported the interest o f cytometric evaluation o f basophils ' activation by inhalant allergens : in allergic patients, we observed a decrease in IgE and an increase in CD45 phenotype "after basophils incubation with allergens. In the present study, we appl ied the same method in 11 allergic patients to muscle relaxants (anaphylaxis and posit ive skin tests for at least the suspected muscle re laxan0 and in 5 control subjects (previous general anesthesia without anaphylaxis and negative skin tests). Basophi ls were incubated with 3 concentrat ions o f 3 muscle relaxants. The test was considered as posi t ive when CD45 antigen upregulation was increased o f at least 15% o f the control assay (without muscle relaxant). A posit ive result was obtained in 10 out o f 11 patients. None o f control subjects has more than 5%. This rapid f low cytometr ic me thod m a y be useful in diagnosis o f drug allergy.