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  • • Distinguishing whether the patient has been bitten and envenomed, bitten but not envenomed, or bitten by a nonvenomous snake is critical prior to starting treatments

    • Treatments may not only cause discomfort but may also produce serious side effects

    • Bite by a venomous snake results in envenomation in only 50-70% of cases

    • Degree of envenomation depends on the size of the snake and the duration of contact

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Venomous Snakes

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  • • Indigenous venomous snakes of North America can be placed in 4 groups:

    • 1. Rattlesnake

      2. Copperhead

      3. Cottonmouth

      4. Coral snake

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Pit Vipers

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  • • Include rattlesnakes, copperhead, and cottonmouth

    • Can be distinguished from nonvenomous snakes by a round mouth and a pit between the eyes and the nares on each side

    • Have retractable canaliculated fangs that can rapidly spring into biting position and deliver venom

    • The large venom glands also give the head a triangular or diamond shape

    • Have vertically oriented elliptiform irises

    • Most deliver a primarily hemotoxic venom

    • Hemotoxic effects are mediated by proteolytic enzymes, peptides, and metalloproteins that cause local tissue destruction directly and by intimal injury to blood vessels, followed by thrombosis and necrosis

    • Activation of the coagulation cascade can occur at multiple points, resulting in net anticoagulation

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Coral Snakes

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  • • Have small mouths, short teeth, and deliver secreted venom into prey through created lacerations

    • Bite lacks the characteristic fang marks of bites by pit vipers, sometimes making it hard to detect

    • Body coloration pattern is red bands immediately adjacent to yellow bands

    • Coral snake venom is primarily neurotoxic

    • Neurotoxic venom can cause dysphagia, dysphonia, diplopia, headache, weakness, and respiratory distress

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Nonvenomous Snakes

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  • • Most snakebites in the United States are from nonvenomous snakes

    • Nonpoisonous snakes such as the red milk snake and the scarlet king snake mimic the bright red, yellow, and black coloration of the coral snake

    • -True coral snakes have red bands immediately adjacent to yellow bands

      -The mimics have black bands immediately adjacent to the red bands, thus the mnemonic: "Red on black, venom lack; red on yellow, kill a fellow"

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Epidemiology

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  • • About 8000 people are bitten by venomous snakes in the United States each year

    • Death from serious envenomation occurs in 9-15 victims per year in the United States

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Symptoms and Signs

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  • • Puncture marks, local ecchymosis and discoloration, vesicles and bullae, and rapid appearance of swelling and edema at the injured area

    • Pain of the bite can be quite severe

    • Additional signs of hypotension, diaphoresis, nausea, weakness, and faintness are common

    • Perioral or peripheral paresthesias, taste changes, and fasciculations

    • Signs suggestive of neurotoxic envenomation include dysphagia, dysphonia, diplopia, headache, weakness, and respiratory distress

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Laboratory Findings

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