Board Review: Summer Emergencies


A 45-year-old male presents to the ED with severe leg, abdominal, and back cramping after being bitten by a spider while working in his barn. He noticed that the spider had a red hourglass shaped marking on its back. On exam he appears uncomfortable due to the pain in his muscles. He is mildly hypertensive but otherwise hemodynamically stable. What is the best treatment at this time?


A. Doxycycline

B. IV Fluids

C. Atropine

D. Benzodiazepines

E. Antivenin 





















D. Black widow spider venom is a neurotoxin that causes release of acetylcholine and norepinephrine at nerve terminals. Patients classically experience significant muscle cramping and may be hypertensive or tachycardic, diaphoretic, or vomiting. Treat muscle cramping with benzodiazepines and provide opioid analgesia. Nitroprusside is typically the agent of choice for hypertension. Black widow antivenom would be indicated if the patient becomes hemodynamically unstable.



Identifying Features

Type of Envenomation

Clinical Features


Widow Spiders


Yellow/red hourglass on belly

Neurotoxic- venom releases acetylcholine and norepinephrine

Rash- target lesion with a blanched center and surrounding erythema with localized diaphoresis


Severe muscle cramping and spasms involving large muscle groups (can mimic acute abdomen) and CNS excitation

Supportive (Benzodiazepines and opioids) and antivenin (Latrodectus antivenin) for severe symptoms

Brown Recluse 



Brown fiddle on cephalothorax

Cytotoxin- venom is thought to release hyaluronidase and sphingomyelinase D

Rash- Initially, a painless bite followed by hemorrhagic bleb formation in the center surrounded by erythema a few hours later


Severe envenomation can cause hemolysis, thrombocytopenia, and renal failure usually 24-72 hrs after the bite


Local wound care


No Antivenin

Coral Snake 


Red next to Yellow, Kill a fellow

Post-synaptically Neurotoxic- competitive inhibition of the muscarinic acetylcholine receptors

Rash- local edema and rash that is mild


Initial Sxs- nausea, vomiting, abdominal pain, dizziness


12 hrs later- neurotoxic which can present as descending muscle weakness, bulbar paralysis (ptosis, opthalmoplegia, dysarthria, and dysphagia)

Supportive Care and respiratory support


Antivenom should be administered to everyone

Pit Vipers


Characteristic pit midway between the eyes and nostrils.


Some will have triangular shaped head, elliptical pupils and fangs


Red on Black, Venom Lack

Coagulopathic and/or hemorrhagic w/ or w/out paralytic features

Rash- fang marks are often undetectable but can cause edema, ecchymosis, and/or hemorrhagic blisters (usually painful and can cause rhabdomyolysis)


Systemic effects: weakness, paresthesias, metallic taste, chest pain, and dyspnea


Hematologic- coagulopathy, thrombocytopenia, bleeding



Antivenin (CroFab)- reserved for moderate to severe envenomations; usually 4-6 vials 






Scott, W et al. (2009). Envenomations: An Overview of Clinical Toxinology for the Primary Care Physician. American Fam Physician, 80(8): 793-802. 15 Oct 2009. <>.



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