Crotalid Envenomation

A typical pit viper case involves an individual bitten on the dorsum of the hand or foot. The fangs penetrate the skin leaving visible marks, and venom is injected into the skin or subcutaneous tissue. Within minutes, proteolytic

Grade I (minimal) Grade II (moderate)

Grade III (severe)

enzymes cause pain and swelling. Edema is usually seen around the injured area within 5 to 30 minutes after the bite but may be delayed for several hours. It progresses rapidly and may involve the entire injured extremity within an hour. Generally, however, edema spreads more slowly, usually over a period of 8 to 36 hours, as a result of lymphatic drainage of the venom. The swelling is most severe after bites of the eastern diamondback rattlesnakes; least severe after bites by the Mojave rattlesnake, copperheads, massasaugas, and pigmy rattlesnakes. Antivenin often stops the progression of swelling but may not reverse it (4,26-28).

Crotalid envenomations also cause sweating and chills, paresthesias, faint-ness, weakness, muscle fasciculations, nausea, and coagulopathies. The diagnosis of intravascular envenomation is based on the extremely rapid onset of severe manifestations, a phenomenon rarely seen with North American rattlesnake dermal or subcutaneous envenomations (9,26,27,39,40).

The cause of death in humans is associated with destruction of the epithelial lining of blood vessels and of erythrocytes, especially in the pulmonary system. Hypovolemic shock and pulmonary edema appear to cause most fatalities. Curry described a death case that was complicated by disseminated intravascular coagulation, adult respiratory distress syndrome, renal failure, left ventricular dysfunction, and many other problems, 15 days after rattlesnake envenomation. This demonstrated the wide range of pathology that can follow a rattlesnake bite (21,27).

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