Complications of Crotalidae antivenin therapy

Polyvalent antivenin is the mainstay of treatment of serious snake envenomation. Its use, however, has been challenged as being unnecessary in minor envenomations and potentially hazardous due to allergic complications. Our institution routinely uses antivenin, and this report focuses on the allergic complications of this therapy. Forty patients with Crotalidae snake bites were evaluated and treated over a 7-year period. Twenty-six patients received a total of 507 vials of antivenin, the dose correlating with the clinical severity of envenomation. All patients were skin tested. Immediate hypersensitivity reactions occurred in six patients (23%). Cutaneous manifestations alone occurred in three of these patients, while systemic anaphylaxis occurred in three. Twenty patients were available for followup, and ten (50%) developed serum sickness. Skin testing was not reliable in predicting the development of immediate (anaphylaxis) or delayed (serum sickness) hypersensitivity reactions. Treatment of antivenin allergic reactions was uniformly effective, with no mortality, minimal morbidity, and no chronic sequelae.