Anaphylactic shock following protamine administration

A severely debilitating anaphylactic reaction occurred in a diabetic when protamine was injected following carotid endarterectomy. The patient had been taking neutral protein Hagedorn (NPH) insulin for several months. Neural and humoral pathways have been well documented as being responsible for its cardiovascular effects; however, little attention has been given to the immunologic mediations of protamine action. On the basis of this report, we suggest that caution is warranted when protamine is administered to patients who may have been sensitized by previous injections. This applies to diabetics, certain blood donors, and previous cardiac surgery patients. Skin testing and specific premedications may be indicated to avoid disastrous consequences.