Pit Viper Snake Envenoming

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T63.091A – Toxic effect of venom of other snake, accidental, initial encounter

217661009 – Poisoning due to viper venom


Pit vipers (family Viperidae; subfamily Crotalinae) include the rattlesnakes, cottonmouth water moccasins, and copperheads. They are native to the United States and are found in all states except Maine, Hawaii, and Alaska. Pit vipers have triangular-shaped heads, elliptical pupils, and heat-sensing pits below and anterior to their eyes. Two elongated, retractable, hollow fangs are located in their anterior upper jaws. When the snake bites, venom is conducted from the venom glands through ducts into the fangs. Rattlesnakes normally have rattles at the tip of their tail (except one Mexican insular species).

Pit viper venom contains components that can affect multiple organ systems and can cause local and systemic injury.

Pit viper bites most commonly occur in intoxicated young men who intentionally try to handle the snake, while other bites occur when victims inadvertently get too close to a snake. Approximately 98% of all venomous snake bites in the Untied States are pit viper bites. Of those, 25% are mild and 20%-25% are "dry" bites (no envenomation).

After a pit viper bite, puncture wounds are usually seen. If envenomation has occurred, pain is generally felt immediately and soft tissue swelling soon follows. The swelling may spread rapidly and be significant. Ecchymoses, petechiae, clear vesicles, hemorrhagic bullae, regional lymphadenopathy, and tissue necrosis may develop, especially if antivenom is not administered.

Nausea and vomiting are common. Other systemic symptoms may include weakness, diaphoresis, chills, dizziness, a change in taste, hypersalivation, tingling or numbness (in the scalp, face, or digits), and muscle fasciculations. Blurred vision or frank blindness due to retinal hemorrhages may occur. With severe envenomations, consumptive coagulopathy, hypotension, pulmonary edema, renal failure, and hypovolemic shock (from bleeding and third spacing) may develop.

Some populations of the Mohave rattlesnake (Crotalus scutulatus) have venom that, unlike most pit viper venoms, is largely neurotoxic. With envenomation by this snake, there may be a paucity of local findings but significant systemic neurotoxicity.

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