If a patient undergoing coronary artery bypass grafting (CABG) experiences unexpected bronchoconstriction and hypotension immediately after protamine administration (to reverse heparin), which mechanism explains the most likely cause?

💡 Explanation

Protamine can trigger non-immunological mast cell degranulation, resulting in the release of histamine and other mediators that cause bronchoconstriction and hypotension. This is because protamine, being a cationic peptide, interacts directly with mast cells, therefore inducing degranulation, rather than complement activation or direct myocardial effects.

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