SNAKE BITES
Key features
Rapid onset of pain and swelling
Symptoms depend on the species and amount of venom injected
Antivenin may be life-saving, but it does not prevent all complica- tions and may cause anaphylaxis
Introduction
Snake bites occur primarily in individuals who engage in outdoor activities, especially camping and hiking. Occupational bite injuries may also affect those who raise snakes and are particularly common in those who extract venom. Death from a snake bite is rare in the US but more common in Africa and Asia.
Clinical features
Snake bites are typically associated with marked edema within an hour of the envenomation. Hemorrhage and necrosis are common. The presence of paired bite marks is often noted.
Treatment
Antivenin therapy is an important part of management and may be of benefit even when administration is delayed. Adverse reactions to antivenin include serum sickness and anaphylaxis. Preparations to treat anaphylaxis should be made before initiating antivenin therapy. Hypersensitivity to antivenin is a particular problem for those who have been previously treated. The evaluation of antivenin reactions is complicated because serum sickness and snake bites share some signs and symptoms, and repeated snake bites can be independently associated with IgE-mediated anaphylaxis. Even in individuals who have never received previous treatment, snake antivenin can result in anaphylactoid reactions.
Thrombocytopenia induced by rattlesnake venom is only partially reversed by antivenin (Crotalidae) administration, and disseminated intravascular coagulation caused by North American crotalid snakebites can occur even after antivenin treatment. The risk of severe bleeding is higher in patients who take antiplatelet drugs.
Tourniquets to limit systemic toxicity from the venom may lead to tissue ischemia if improperly applied. Studies have not been performed for all snakes, but tourniquet application appears to be of little benefit.