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Snake Bite

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Snake Bite, SnakeBite, Rattlesnake, Copperhead, Cottonmouth, Coral Snake, Snake Venom, Snake Envenomation, Crotalid Venom, Pit Viper Venom, Elapid Venom

  • Epidemiology
  1. U.S. Incidence
    1. Total: 45,000 Snake Bites in U.S. per year
    2. Venomous bites: 8000 in U.S. per year
    3. Deaths from Snake Bite in U.S.: 12 or less per year
    4. Envonomation occurs in 75% of U.S. poisonous SnakeBites
  2. Worldwide Snake Bites (esp. Africa, Asia, Latin America)
    1. Incidence: 5.4 Million Snake Bites/year worldwide (50% are venomous)
    2. Roughly 100,000 deaths per year worldwide from Snake Bites
    3. Roughly 300,000 amputations per year worldwide from Snake Bites
  • Etiology
  • U.S. Poisonous snakes
  1. Coral Snakes (Family Elapidae)
    1. Nonaggressive poisonous snakes of the southern U.S.
    2. Transfer venom via chewing instead of injection
    3. Arizona Coral Snake (Micruroides Euryxanthus)
    4. Texas Coral Snake (Micrurus Tener)
    5. Eastern Coral Snake (Micrurus Fulvius) - primarily in the southeast United States
  2. Pit Vipers or Crotalidae (99% U.S. venomous bites)
    1. Rattlesnake (Crotalus or Sisturus genera)
      1. Most common poisonous snake in U.S.
      2. Potent venom
      3. Responsible for 95% of deaths (esp. Diamondback)
    2. Cottonmouth, water moccasin (Agkistrodon piscivorous)
      1. Aggressive water snakes in Southeastern U.S.
      2. Moderately potent venom
    3. Copperhead (Agkistrodan contortix)
      1. Least potent venom
  • Signs and Symptoms
  • Pit Vipers (except Mojave rattler)
  1. Snake characteristics
    1. Long movable fangs cause skin puncture marks
    2. Broad triangular heads with elliptical eyes and heat sensing pits between the eyes and nostrils
    3. Up to 25% of pit viper bites deliver no venom (dry bites)
  2. Venom alters Coagulation Factors (via thrombin-like glycoproteins), tissue necrosis
    1. Immediate pain and burning at bite site
    2. Within a few minutes redness and swelling develops
    3. Bite site develops a purplish discoloration
  3. Generalized signs and symptoms (Hemotoxic effects)
    1. Nausea and Vomiting
    2. Dizziness and Hypotension
    3. Weakness
    4. Sweats and chills
    5. Metallic or Rubbery taste in mouth
  4. Generalized neurotoxic effects (only with U.S. West Coast Rattlesnakes: Mojave, tiger and some timber Rattlesnakes)
    1. Muscle fasciculations
  5. Systemic complications
    1. Disseminated Intravascular Coagulation (DIC)
    2. Acute Renal Failure
    3. Hypovolemic shock (7% of cases)
    4. Rhabdomyolysis (if muscle fasciculations)
  6. Course
    1. Not immediately fatal unless Envenomation into vein
  • Signs and Symptoms
  • Coral Snakes
  1. Characteristics
    1. Small fixed fangs cause tiny semicircular scratches
    2. Venom contains a Neurotoxin (primarily affecting acetylcholine receptors)
    3. Coral Snake: Red stripe next to yellow stripe ("Red next to yellow, you're a dead fellow")
      1. Contrast with King Snake
        1. Red stripe next to black stripe ("Red next to black, venom they lack")
      2. This rule applies only in the U.S.
        1. Outside the U.S., Red and Black snakes may be venomous
  2. Generalized symptoms may be delayed 1-8 hours
    1. Drowsiness, Weakness
    2. Paresthesias with numbness at bite site
    3. Bulbar Paralysis with Ptosis, Ophthalmoplegia or Dysphagia
    4. Blurred vision
    5. Slurred speech
    6. Salivation
    7. Seizures
  3. Systemic complications
    1. Descending Flaccid Paralysis
    2. Cardiac Arrest or respiratory arrest may occur
  • History
  1. Snake appearance (photo if available) and suspected variety or species
  2. Time elapsed since Snake Bite
  3. Symptoms and their timing since the Snake Bite occurred
  4. Last tetanus Vaccination
  • Management
  • First Aid in field
  1. Get to a medical facility as soon as possible
  2. Calm and reassure patient
  3. Attempt to identify snake type from a distance (photo, color and pattern description)
    1. Do not try to capture the snake for Identification
    2. Do not attempt to handle even a dead snake (Envenomations occur from intact bite reflex)
  4. Do not leave a patient alone
  5. Have the patient lie down
  6. Immobilize bite area
    1. Rattlesnake: Level with the heart
    2. Non-Rattlesnake Pit Viper: Above the level of the heart (may reduce local tissue swelling and inflammation)
    3. Coral Snake: Below the level of the heart (may reduce systemic toxin distribution)
  7. Remove jewelry or clothing that tighten with swelling
  8. Clean the bite area with soap and water
    1. Irrigate the wound with clean water or saline
    2. Apply antiseptic solution and gauze if available
  9. Mechanical venom suction devices are no longer recommended (only remove 2% of venom)
    1. Previously small vacuum venom extractor devices were recommended
      1. Had previously been indicated within 5 minutes of bite, left in place for 30 min
    2. Do not cut wound or try to suck out venom
    3. Avoid harmful methods (see below) at bite site
  10. Low pressure constriction band (NOT a Tourniquet)
    1. Indicated if medical assistance is >1 hour away and neurotoxic effects are expected
      1. Primarily indicated for Coral Snake bites (not pit vipers)
    2. Wrap a band (ACE, belt, sock) 2-3 inches above bite
      1. Band should be wide and flat
      2. Band applied between bite site and heart
    3. Do not cut off arterial circulation
      1. Pressure: 20 mmHg
      2. Be able to slip a finger between band and skin
    4. Leave band in place until medical facility
    5. Contraindications to low pressure constriction band
      1. Gila Monster
      2. Copperhead
      3. Water moccasin
      4. Pygmy Rattlesnake
  • Labs
  1. Blood Type and cross match
  2. Urinalysis
  3. Chemistry panel (e.g. Chem8)
    1. Renal Function tests (BUN and Creatinine)
    2. Serum electrolytes
    3. Serum Glucose
  4. Complete Blood Count with Platelet Count
    1. Thrombocytopenia may be delayed (repeat Platelet Count in 7-10 days)
  5. Liver Function Tests
  6. Coagulation Factors (draw baseline and at 12 hours)
    1. Prothrombin Time (PT)
    2. Partial Thromboplastin Time (PTT)
    3. Fibrinogen
    4. Fibrin Split Products
    5. D-Dimer
    6. Creatine Phosphokinase (CPK)
  7. Other studies that may be indicated (esp. Coral Snake bites)
    1. Arterial Blood Gas (ABG)
    2. Waveform Capnography
    3. Pulmonary Function Tests
    4. Troponin I
  • Diagnostics
  • Management
  • Emergency Department
  1. ABC Management
  2. Antivenom
    1. See Snake Antivenin
    2. Use now even for mild pit viper bites if progressive erythema, swelling and pain
  3. Contact poison control immediately (in U.S., 1-800-222-1222)
    1. Local zoo herpetologist may also be helpful in snake identification
  4. Clean and irrigate the wound
  5. Tetanus Toxoid
  6. Opioid Analgesics are often needed (esp. pit viper bites)
  7. Do not draw blood or start IV in affected extremity
  8. Start Intravenous Fluids
  9. Prophylactic antibiotics are not recommended
  10. Suspected pit viper bite management (local swelling and inflammation)
    1. Observe asymptomatic patients 8-12 hours after bite
    2. Monitor frequent pulse checks at a point distal to the bite site
    3. Mark leading edge of bite site swelling and erythema every 30 minutes
    4. Hospital admission for any patient who received antivenom
    5. Indications for discharge
      1. No proximal spread of extremity findings
      2. Normal laboratory studies
      3. Patient able to return immediately for worsening
      4. Patient should return for Coagulopathy signs or pain not relieved with limb elevation
  11. Suspected Coral Snake bite management
    1. Observe asymptomatic patient for at least 12-24 hours
    2. Monitor neurologic status and respiratory status closely
    3. Requires immediate treatment and antivenin
    4. Neurologic complications may be delayed
    5. Consider Anticholinergics (Atropine, neostigmine)
    6. Hospital admission for any patient who received antivenom
    7. Intubation and Ventilator support may be required
      1. Indicated for forced Vital Capacity <50% of predicted
  • Precautions
  • Avoid harmful methods
  1. Do not cut skin at bite site
  2. Fasciotomy is rarely indicated
    1. Compartment Syndrome may be controlled by antivenin
    2. Only Consider if hourly serial ICP >30 mmHg
  3. Do not use electric shock or stun gun at bite site
  4. Do not apply tightly constricting Tourniquet
  5. Do not administer antivenin in the field
    1. Risk of Anaphylaxis
  6. Delayed Thrombocytopenia (antivenin-refractory) may occur
    1. Recheck Platelet Count again in 7-10 days
  • Prevention
  1. On coming upon a snake:
    1. Slowly and quietly move away, and allow it to escape
    2. Do not expect a warning before they strike
      1. Most snakes do not hiss or rattle before striking
    3. Do not handle any snake (even if snake appears dead)
  2. Be alert in areas commonly inhabited by snakes
    1. Hiking, picnicking, camping and firewood areas
    2. Water areas
    3. Tall grass, underbrush, abandoned buildings
    4. Piles of logs, rocks, and branches
  3. Be careful of areas of decreased visibility
    1. Avoid reaching into holes and crevices
    2. Avoid jumping over logs and fences
    3. Pull logs or rocks toward you when turning over
    4. Avoid placing fingers under objects being lifted
  4. Prepare for a hike
    1. Wear boots and long pants
    2. Carry a flashlight for nighttime conditions
    3. Hike with a companion
  5. Reduce residential risks of Snake Bite
    1. Provide lighting for yard, sidewalks, and patio
    2. Keep yard mowed and bushes pruned
    3. Keep home free of mice