Unpredictable anaphylactic reaction to protamine sulfate

Anaphylactic reactions to protamine administration often can be predicted by the presence of patient risk factors. In the case described, an anaphylactic reaction to protamine occurred in a patient without identifiable risk factors. A history of prior protamine exposure, fish allergy, or vasectomy suggests patients may be at greater risk for anaphylactic response to protamine; however, patients can develop anaphylaxis in the absence of such factors.