[Prospective preoperative survey of 300 patients using prick tests with muscle relaxants]

It is now well established that the retrospective diagnosis of anaphylaxis to muscle relaxants may be based on skin prick testing. These tests, which use undiluted solutions of muscle relaxants, are as sensitive, specific and reproducible as intradermal tests for the diagnosis of IgE related adverse reactions to muscle relaxants. The rate of muscle relaxant anaphylaxis (1/1 500 to 1/5 000) justifies its prevention based on a possible latent sensitization. A prospective investigation was carried out in 300 surgical patients scheduled for general anaesthesia. Prick tests were carried out using the 6 available muscle relaxants: suxamethonium, gallamine, alcuronium, pancuronium, vecuronium and atracurium. The wheal the drug might produce was compared with that obtained with codeine phosphate (a histamine releasing drug). Thirty-seven patients (13%) were considered to be atopic; 262 (87%) had undergone a previous anaesthesia. Three percent (n = 11) of tests were positive for atracurium. The wheal produced by atracurium was in favour of non-specific histamine release. One test was found positive for suxamethonium. Confirmation of this probable latent sensitization was unfortunately not possible. There were no other positive skin tests. Muscle relaxants were subsequently used in 58 patients (80% vecuronium) without any problem. Skin prick testing should be used on a larger scale to detect latent sensitization. However, predictive skin tests with atracurium should be avoided, as wheal reactions with this drug are probably due to non-specific histamine release.