NEJM: An Overview of Snake Envenomation

Written by Amanda Mathews

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Snake envenomation has a large global health burden with a variety of clinical presentations from benign to life threatening. Early use of antivenom (if available), good supportive care, and admission for further treatment and observation is the best management regardless of the snake species involved.

Why does this matter?
Snake envenomation occurs on every continent outside of Antarctica and accounts for an estimated 80,000-130,000 deaths worldwide annually. As emergency physicians, we may be called on to treat snake bites from both native and non-native snakes.

Dancing the mamba is fun, being bitten by one…
This review article covered the pathophysiology, diagnosis, and management of snake envenomation.

Pathophysiology of Toxin Effects: 

  • Direct effects: Damage to the lymphatic system causes localized edema and pain which can present as a clinical mimic of compartment syndrome with normal compartment pressures.

  • Coagulation effects: Procoagulant toxins promote consumptive coagulopathy leading to increased bleeding risk. Bites from pit vipers in particular lead to thrombocytopenia.

  • Neurologic effects: Snake venoms can contain pre- or postsynaptic toxins or a mixture of both. Either type can cause a progressive descending paralysis starting with the bulbar muscles and leading to respiratory compromise. Postsynaptic neurotoxins are reversed by antivenom binding; antivenom for presynaptic neurotoxins must be given very early, while still extracellular, to be effective.

  • Nephrotoxic effects: These occur due to direct venom effects, rhabdomyolysis, or coagulopathy and range from acute kidney injury to permanent damage and chronic kidney disease.

Diagnosis

  • Being able to accurately identify the snake species is best, but don’t try to catch the snake to bring it in. Nobody wants to see it that bad.

  • In the absence of a positive ID, the patient’s presentation, appearance of the wound, and clinical course will allow you to make appropriate treatment decisions.

Pre-hospital care:

  1. Get away from the snake! Medic ≠ snakecharmer. Scene safety is key.

  2. Loosely splint affected extremity.

  3. Anticipate swelling and remove jewelry or constrictive clothing.

  4. Initiate transport.

Emergency Department Care:

  1. Inspect wounds for retained foreign bodies such as fangs or teeth.

  2. Call local poison control or consult the WHO Antivenom database.

  3. If it does not appear envenomation has occurred, update tetanus vaccine and observe for 6-24 hours.

  4. Give antivenom if available. Early use is associated with the best outcomes. Elevate affected body part above the heart. Give enough in an initial dose to stop or reverse the clinical signs of the venom.

  5. Continued supportive care: analgesia, fluid resuscitate, airway interventions if needed

  6. Admission: general medicine or ICU depending on systemic symptoms and vital signs. Patients may need redosing of anti-venom in the first 24 hours and even up to multiple days later.

Reviewed and edited by Aaron Lacy and Clay Smith

Source
Snake Envenomation. N Engl J Med. 2022 Jan 6;386(1):68-78. doi: 10.1056/NEJMra2105228.

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