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