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Leslie V. Boyer, MD; Steven A. Seifert, MD; Richard F. Clark, MD; Jude T. McNally, RPh; Saralyn R. Williams, MD; Sean P. Nordt, PharmD; Frank G. Walter, MD; Richard C. Dart, MD, PhD

Arch Intern Med. 1999;159:706-710.

Background  Coagulation abnormalities following crotaline (pit viper) snakebite have traditionally been considered short-lived, but laboratory studies have rarely been reported beyond the first few days of treatment for envenomation. During the course of an antivenom clinical trial, we observed coagulation defects as late as 2 weeks following envenomation.

Objectives  To document and characterize the recurrence or persistence of coagulopathy among patients envenomed by pit vipers and treated with a Fab antivenom.

Methods  Patients with moderate pit viper envenomation were enrolled in a multicenter, prospective clinical trial. A Fab-based antivenom preparation, antivenom polyvalent crotalid (ovine) Fab, was administered in all cases. Platelet count, fibrinogen level, presence of fibrin split products, prothrombin 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, persistent, or late coagulopathy 2 to 14 days after envenomation. Thrombocytopenia occurred in patients with prior thrombocytopenia; hypofibrinogenemia occurred only in those with prior hypofibrinogenemia or positive fibrin split products. No patient experienced significant spontaneous bleeding. One patient with coagulopathy developed minor bleeding following minor surgery 12 days after envenomation.

Conclusions  Prolonged or recurrent coagulopathy may occur after envenomation by North American pit vipers. Patients treated with Fab-based antivenom may benefit from periodic rather than single-bolus dosing. Patients with coagulopathy should undergo close monitoring during the first 2 weeks after snakebite.

From the Departments of Pediatrics (Dr Boyer) and Surgery (Dr Walter) and College of Pharmacy (Mr McNally), University of Arizona Health Sciences Center and Arizona Poison and Drug Information Center (Dr Boyer and Mr McNally) and Department of Emergency Medicine, Kino Community Hospital (Dr Seifert), Tucson, Ariz; Department of Emergency Medicine and California Poison Control System, San Diego Division (Drs Clark, Williams, and Nordt), and Department of Emergency Medicine, University of California at San Diego (Drs Williams and Nordt); and Rocky Mountain Poison and Drug Center, Denver Health Department, and Colorado Emergency Medicine Research Center, University of Colorado, Denver (Dr Dart).

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