Snake Bite

Aka: Snake Bite, SnakeBite, Rattlesnake, Copperhead, Cottonmouth, Coral Snake, Snake Venom, Snake Envenomation

1. See Also
   1. Snake Antivenin
   2. Neurotoxin
2. Epidemiology: 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
3. Etiology: U.S. Poisonous snakes
   1. Coral Snakes (Family Elapidae)
      1. Nonaggressive snakes of the southern U.S.
      2. Transfer venom via chewing instead of injection
   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
4. Signs and Symptoms: Pit Vipers (except Mojave rattler)
   1. Long movable fangs cause skin puncture marks
   2. Venom alters Coagulation Factors, 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 symptoms (Hemotoxic effects)
      1. Nausea and Vomiting
      2. Dizziness
      3. Weakness
      4. Sweats and chills
      5. Metallic or Rubbery taste in mouth
   4. Systemic complications
      1. Disseminated Intravascular Coagulation (DIC)
      2. Acute Renal Failure
      3. Hypovolemic shock (7% of cases)
   5. Course
      1. Not immediately fatal unless Envenomation into vein
5. Signs and Symptoms: Coral Snakes
   1. Small fixed fangs cause tiny semicircular scratches
   2. Venom contains a Neurotoxin
   3. Generalized symptoms may be delayed 1-8 hours
      1. Drowsiness, Weakness
      2. Paresthesias with numbness at bite site
      3. Blurred vision
      4. Slurred speech
      5. Salivation
      6. Seizures
   4. Systemic complications
      1. Paralysis
      2. Cardiac Arrest or respiratory arrest may occur
6. 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
      1. Do not try to capture the snake for Identification
   4. Do not leave a patient alone
   5. Have the patient lie down
   6. Immobilize bite area below the level of the heart
   7. Remove jewelry or clothing that tighten with swelling
   8. Clean the bite area with soap and water
      1. Apply antiseptic solution and gauze if available
   9. Use a venom extractor device within 5 minutes of bite
      1. Do not cut wound or try to suck out venom
      2. Use vacuum-suction device to extract venom
      3. Venom extractor left in place for 30 minutes
      4. Avoid harmful methods (see below) at bite site
   10. Low pressure constriction band
       1. Indicated if medical assistance is >1 hour away and neurotoxic effects are expected
       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
7. 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. Liver Function Tests
   5. Coagulation Factors (draw baseline and at 12 hours)
      1. Complete Blood Count with Platelet Count
      2. Prothrombin Time (PT)
      3. Partial Thromboplastin Time (PTT)
      4. Fibrinogen
      5. D-Dimer
      6. Creatine Phosphokinase (CPK)
   6. Other studies that may be indicated
      1. Electrocardiogram (EKG)
      2. Arterial Blood Gas (ABG)
      3. Troponin I
8. Management: Emergency Department
   1. See Snake Antivenin
   2. Contact poison control immediately
   3. Clean wound
   4. Tetanus Toxoid or immune globulin if underimmunized
   5. Do not draw blood or start IV in affected extremity
   6. Start intravenous fluids
   7. Prophylactic antibiotics are not recommended
   8. Suspected pit viper bite management
      1. Observe asymptomatic patients 12 hours after bite
      2. Mark leading edge of bite site swelling q30 minutes
      3. Indications for discharge
         1. No proximal spread of extremity findings
         2. Normal laboratory studies
         3. Patient able to return immediately for worsening
   9. Suspected Coral Snake bite management
      1. Observe asymptomatic patient for at least 24 hours
      2. Requires immediate treatment and antivenin
9. 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
10. 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
11. References
    1. (1998) Postgrad Med 103(4): 311
    2. Juckett (2002) Am Fam Physician 65(7):1367-74
    3. McKinney (2001) Ann Emerg Med 37(2):168-74