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THE MORNING REPORT

The Best in FOAM Education

  • Lauren Lynch, MD

Bites and Envenomations

Spider Bites

  • Can be painful or painless​

  • More common with tight clothing​

  • Most spider bites in the US are due to brown recluse or black widow

Brown Recluse (Loxoceles) Spider Bites​

  • Identification

    • brown fiddle shape on cephalothorax



  • Presentation:​

    • Burning/itching/pain/redness at the site​

    • Deep blue or purple area, large red outer ring, and white inner ring ​

    • Necrotic open sore or blister​

    • Headache​

    • Myalgia​

    • Fever​

    • Rash​

    • Nausea/vomiting​

  • Treatment:​

    • Supportive - warm compress, treat cellulitis, consider tetanus booster, analgesia, hydration​

    • Surgical debridement if severe (wait for margins to stop expanding)​

Black Widow (Latrodectus) Spider Bites​

  • Identification

    • ​Red/yellow hourglass on abdomen



  • Pathophysiology

    • a-Latrotoxin - presynaptic neurotoxin​

    • Depolarizes CNS neurons, uncontrolled exocytosis of neurotransmitters​

  • Symptoms:​

    • Weakness/tremors/paralysis - especially in the legs​

    • Immediate pain/burning/swelling/erythema @ site​

    • Cramping pain​

    • Muscle stiffness​

    • Headache​

    • SOB​

    • Dizziness​

    • Rash/itching​

    • Restlessness/anxiety​

    • Diaphoresis​

    • Eyelid swelling​

    • Nausea/vomiting​

    • Salivation/tearing of the eyes

  • Treatment​

    • Supportive; opioids, benzos; intubation if respiratory failure​

    • Antivenom if symptoms are severe​

    • Tetanus prophylaxis​

Black Widow (Latrodectus)

Brown Recluse (Loxoceles)

Identifying features

​Red/yellow hourglass on abdomen

brown fiddle shape on cephalothorax

Venom

Neurotoxin

cytotoxin

Clinical effects

Severe muscle cramping & CNS excitation

Treatment

Supportive (opioids and benzodiazepines)

Supportive (local wound care)

Antivenom

Yes, reserved for severe symptoms

No

Snakes

  • Four families of venomous snakes worldwide​

  • Atractaspididae​

  • Colubridae​

    • Boomslang snake​

  • Elapidae​

    • Eastern coral snake​

    • Texas coral snake​

    • Arizona coral snake​

    • Cobras​

    • Kraits​

    • Mambas​

  • Viperidae​

    • Copperhead​

    • Cottonmouth​

    • Rattlesnake​

    • Western diamondback​

Coral Snake (Elapidae) Envenomation

  • Identification

    • Red on yellow, kill a fellow

    • Red on black, venom lack

    • ***only applies in the US


  • Pathophysiology

    • Toxins: phospholipases A2 and “three finger toxins”​

    • Irreversibly binds acetylcholine receptors resulting in systemic toxicity

    • marked systemic neurotoxicity

  • Presentation

    • symptoms can be delayed up to 13 hours​

    • Local numbness​

    • Cranial nerve palsies​

    • AMS​

    • Weakness​

    • Respiratory failure​

    • Hypovolemic shock​

    • (rarely) DIC

  • Management

    • Supportive care

    • Antivenom

      • ***High risk of anaphylaxis

      • should not be used in those with horse allergies

    • admission for observation

Crotaline AKA Pit Vipers (subfamily of Viperidae) Envenomation

  • Identification

    • Rattlesnakes, copperheads​, western diamondbacks, cotton mouths

    • triangular shaped head

    • nostril pits (heat-sensing organs anteroinferior to the eye)

    • Elliptical pupils



  • Symptoms​

    • N/V​

    • Oral numbness/tingling​

    • Dizziness​

    • Muscle fasciculations​

    • Local tissue damage/swelling​

    • Localized pain​

    • Coagulopathies​

    • Platelet dysfunction​

  • Treatment​

    • Observe at least 6-8 hours​

    • Antivenom

      • Crotalidae polyvalent immune Fab (CroFab)

        • Sheep product. Few allergic manifestations.

      • Antivenom polyvalent

        • older formulations from horse serum

        • administor only for moderate - severe envenomations

      • Antivenom if:​

        • Progressive edema​

        • Abnormal labs (platelets <100,000, fibrinogen <100)​

        • Systemic symptoms (AMS, unstable VS)​


Lauren Lynch, MD

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