Snake bites

Background

Coral snake

Rattlesnake

• An average of 5000 native venomous snakebites are reported to US poison centers annually
• In the United States, snake bites can be organized into Crotaline (Pit Vipers) and Elapidae (Coral Snakes)
• Crotalidae family also includes rattlesnakes, Sistrurus and Agkistrodon species (water moccasins and copperheads).
• Risk Factors: "The 'T's" Testosterone, Tequila, Tshirt, Tattoos, Toothless, Teasing, Trailer park, Truck

Venom

• Snake venom is a mixture of proteins, peptides, lipids, and metal ions.
• Many bites can be "dry bites" where no venom is released, about ~1/4

Clinical Features

• Local injury - punctures marks from fangs not always visible; erythema, and edema
• Ooze at fang mark reliable sign of envenomation
• Nausea/vomiting

Differential Diagnosis

Envenomations, bites and stings

• Hymenoptera stings (bees, wasps, ants)
• Mammalian bites
  • Closed fist infection (Fight bite)
  • Dog bite
• Marine toxins and envenomations
  • Toxins (ciguatera, neurotoxic shellfish poisoning, paralytic shellfish poisoning, scombroid, tetrodotoxin
  • Stingers (stingray injury)
  • Venomous fish (catfish, zebrafish, scorpion fish, stonefish, cone shells, lionfish, sea urchins)
  • Nematocysts (coral reef, fire coral, box jellyfish, sea wasp, portuguese man-of-war, sea anemones)
  • Phylum porifera (sponges)
  • Bites (alligator/crocodile, octopus, shark)
• Scorpion envenomation
• Reptile envenomation
  • Snake bites
    • Crotaline (Pit Vipers)
    • Elapidae (Coral Snakes)
  • Lizard bites
• Spider bites
  • Black widow
  • Brown recluse
  • Tarantula
  • Funnel-web spider bite
  • Armed spider bite

Evaluation

• Clinical Diagnosis
• Evaluate for compartment syndrome (see below)
• CBC, coags: Thrombocytopenia and elevated INR can occur in Crotaline envenomations.

Management

Local Care

• Do:
  • Remove all jewelry
  • Mark the leading edge of erythema/edema
• Do not:
  • Attempt to suck out the venom
  • Place the affected part in cold water
  • Use a tourniquet or wrap
  • Antivenom is first line treatment for compartment syndrome; fasciotomy is last resort if elevated pressures persist.

Supportive care

• IVF and pressors if needed for hypotension
• Blood components rarely needed
• Treatment mainly depends upon the presence of an envenomation
• Indications:
  • Progression of local injury - pain, swelling, ecchymosis
  • Coagulopathy - elevated PT/PTT/INR, low fibrinogen, thrombocytopenia
  • Systemic effects - hypotension, altered mental status, nausea and vomiting, paresthesias
• Always provide supportive care and treat local effects of any wounds
• Irrigation of the wound is necessary regardless of the type of snake bite
• Debridement and removal of devitalized tissue may be necessary for severe bites
• Evidence does not support use of empiric antibiotics to prevent secondary infection
• Compartment syndrome has been documented with crotaline envenomation, but current literature does not support use of fasciotomy. Treatment should focus on antivenom.

Antivenom

• Snake specific treatments depend upon Coral snake or Pit viper envenomations

Disposition

• All snake bites with evidence of envenomations should have a period of observation and possible hospitalization
• Old bites can be assessed and discharged if no evidence of envenomation.

See Also

• Envenomations, bites and stings
• Crotaline (Pit Vipers)
• Elapidae (Coral Snakes)