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