Recurrent and persistent coagulopathy following pit viper envenomation

Background: Coagulation abnormalities following crotaline (pit viper) snake bite have traditionally been considered short-lived, but laboratory studies have rarely been reported beyond the first few days of treatment for enven omation. During the course of an antivenom clinical trial, we observed coag ulation defects as late as 2 weeks following envenomation. Objectives: To document and characterize the recurrence or persistence of c oagulopathy among patients envenomed by pit vipers and treated with a Fab a ntivenom. Methods: Patients with moderate Pit viper envenomation were enrolled in a m ulticenter, prospective clinical trial. A Fab-based antivenom preparation, antivenom polyvalent crotalid (ovine) Fab, was administered in all cases. P latelet count, fibrinogen level, presence of fibrin split products, prothro mbin time, and partial thromboplastin time were determined before treatment and at standard intervals during the following 2 weeks. Results: Of 38 patients completing the study, 20 (53%) had recurrent, persi stent, or late coagulopathy 2 to 14 days after envenomation. Thrombocytopen ia occurred in patients with prior thrombocytopenia; hypofibrinogenemia occ urred only in those with prior hypofibrinogenemia or positive fibrin split products. No patient experienced significant spontaneous bleeding. One pati ent with coagulopathy developed minor bleeding following minor surgery 12 d ays after envenomation. Conclusions: Prolonged or recurrent coagulopathy may occur after envenomati on by North American pit vipers. Patients treated with Fab-based antivenom may benefit from periodic rather than single-bolus dosing. Patients with co agulopathy should undergo close monitoring during the first 2 weeks after s nakebite.