Intraoperative protamine-induced anaphylaxis suggesting the possible involvement of an immunoglobulin E-dependent pathway based on basophil activation tests: a case report

Abstract Background Protamine is a recognized cause of perioperative anaphylaxis; however, its underlying mechanism remains incompletely understood. We report a case of protamine-induced anaphylaxis, in which skin testing and basophil activation tests (BATs) suggested the possible involvement of an immunoglobulin (Ig) E-dependent mechanism. Case presentation A 75-year-old man underwent endovascular aortic repair under general anesthesia. Two minutes after protamine administration, he developed severe hypotension and increased airway resistance. His condition improved after adrenaline administration. Elevated serum tryptase levels supported a diagnosis of anaphylaxis. Skin tests performed seven weeks later were positive only for protamine. BATs demonstrated basophil activation following protamine stimulation compared with a control. Wortmannin, a phosphoinositide 3-kinase inhibitor suppressing IgE-mediated basophil activation, almost completely suppressed protamine-induced activation, but had only a partial effect on formyl methionyl leucyl phenylalanine-induced activation. Conclusions Protamine-induced anaphylaxis in this case may have involved an IgE-dependent mechanism. BATs may help identify causative agents of perioperative anaphylaxis and provide insight into the underlying immunological mechanism.