Medical treatment options for pit viper snakebites in dogs

Abstract

OBJECTIVE: To provide a review and update on the medical management of pit viper envenomation in dogs. ETIOLOGY: Pit viper snake (Crotalidae) envenomation in dogs is a common emergency in the United States. At least 50 enzymes contribute to snake venom potency that causes soft tissue damage, vasculotoxicity, coagulopathy, cytotoxicity, and necrosis. DIAGNOSIS: Snakebite envenomation may be identified by fang puncture wounds but primarily as a focal site with a rapid onset of severe swelling, hemorrhage, pain, and potentially necrosis. Crotalid venom causes hematologic abnormalities, local tissue damage, hypotension, and occasionally neurological impairment. The most marked hematologic abnormalities include thrombocytopenia, hemolytic anemia, and various forms of coagulopathy, including defibrination without disseminated intravascular coagulation (in North America), summarized as a venom-induced coagulopathy. THERAPY: The mainstay of treatment includes intravenous crystalloid fluid therapy, antivenom, and analgesic medications. Currently available antivenom products include a mixed polyvalent Antivenin (Crotalidae) Polyvalent (ACP(a)), and Crotalinae polyvalent immune Fab (Crofab(b)). There are products from Mexico and Costa Rica that have limited availability, a similar imported Fab product (Antivipmyn(c)), and a polyspecific antivenom (Polyvet-ICP(d)), respectively. Glucocorticoids, nonsteroidal antiinflammatory drugs (NSAIDs) and antihistamines are not included in the majority of recommended treatment protocols by world authorities; however, there are some reports that describe their use. Antimicrobial therapy and blood products are used only when clinically indicated. There is a vaccine available, but at present, it is of unknown efficacy because of a lack of documented scientific information. PROGNOSIS: Mortality from North American crotalid envenomation is generally rare and is influenced by several variables, including the amount of venom injected, the size and species of snake, the size of the victim, the location of the bite, time elapsed until treatment, and the therapy initiated. Mortality rates range from 1% to 30%.