Snake bites

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Crotaline (Pit Vipers)

Background

  • Includes rattlesnakes and copperheads
  • Venom causes local tissue injury, hemolysis, coagulopathy, neuromuscular dysfunction
  • Up to 25% of bites are dry bites

Clinical Features

  1. Fang marks, localized pain, progressive edema extending from bite site
    1. Edema near the airway or in muscle compartment may threaten life or limb
  2. Nausea/vomiting, oral numbness/tingling, dizziness, muscle fasciculations
  3. Ecchymoses may appear within minutes to hours

Diagnosis

  1. Must have a snakebite + evidence of tissue injury:
    1. Local injury (swelling, pain, ecchymosis)
    2. Hematologic abnormality (thrombocytopenia, elevated INR, hypofibrinogenemia)
    3. Systemic effects (oral swelling/paresthesias, metallic taste, hypotension, tachycardia)
  2. Absence of all of the above 8-12hr after bite indicates dry bite

Work-Up

  1. CBC
  2. Coags
  3. Fibrinogen
  4. FDP
  5. Chemistry

Treatment

  1. Local Care
    1. Do not:
      1. Attempt to suck out the venom
      2. Place the affected part in cold water
      3. Use a tourniquet
    2. Do:
      1. Use a constriction band
        1. Apply elastic bandage or piece of clothing circumferentially above bite
        2. Tighten so superficial venous/lymphatic flow is restricted while arterial flow is not
      2. Immobilize limb in a neutral position
  2. Antivenom
    1. Crotalidae Polyvalent Immune Fab (FabAV)
    2. Indications:
      1. Worsening of local injury
      2. Abnormal results on lab tests
      3. Systemic manifestations (unstable vitals or AMS)
    3. Administration
      1. The total volume but NOT the number of vials may be reduced in small children
      2. Establish initial control of envenomation by giving 4-6 vials
        1. Control achieved? (Cessation of progression of all components of envenomation)
          1. If yes infuse 2-vial doses at 6, 12, and 18hr after initial control achieved
          2. If no repeat infusion of 4-6 vials and then re-evaluate for control
    4. Envenomation control measurement
      1. Must observe for progression of envenomation during and after antivenom infusion
        1. Measure limb circumference at several site above and below bite
        2. Mark advancing border of edema q30min
        3. Repeat labs q4hr or after each course of antivenom (whichever is more frequent)
    5. Side Effects
      1. Acute reactions occur in <10% pts
      2. If occurs stop infusion and give antihistamines / epi if needed
  3. Supportive care
    1. IVF and pressors if needed for hypotension
    2. Blood component replacement indicated if antivenom fails to stop active bleeding
  4. Compartment Syndrome
    1. If signs of compartment syndrome are present and pressure >30:
      1. Elevate limb
      2. Administer mannitol 1-2gm/kg over 30min
      3. Simulataneously administer additional FabAV 4-6 vials IV over 60min
      4. If elevated compartment pressure persists another 60min consider fasciotomy

Disposition

  1. Must observe all snakebite pts for at least 8hr before determining patient disposition
    1. Bites that initially appear innocuous and labs normal at presentation can be deceptive
  2. Discharge if symptom-free after 8hr
  3. Admit all pts receiving antivenom to the ICU
  4. Admit pts to the ward if have completed or do not require further antivenom therapy

Coral Snakes

Background

  1. All coral snakes are brightly colored with black, red, and yellow rings
    1. Red and yellow rings touch in coral snakes, but are separated in nonpoisonous mimics
      1. "Red touch yellow, kills a fellow; red touch black, venom lack"

Clinical Features

  1. Local injury is often minimal
  2. Venom effects may develop hours after a bite

Treatment

  1. Antivenom
    1. Give 3-5 vials of Antivenin to ALL pts who have definitely been bitten
      1. It may not be possible to prevent further effects or reverse effects once they develop
      2. Additional doses of antivenom are reserved for cases in which symptoms/signs appear
  2. Monitor for respiratory respiratory failure

Disposition

  1. Admit all pts (even if initially symptom free)

Source

Tintinalli