A 42-year-old hiker comes in at dusk with a crescent of punctures on his ankle, mud still drying on his boot, and a swelling calf that seems to be ballooning by the minute. He’s pale, nauseated, and keeps asking if the tingling in his mouth means “the venom is in my blood.” The leg is starting to hurt more than it should, and the tourniquet someone tied at the trailhead is still clenched above the knee. The question now is not what bit him, but which bite pattern this is — and how fast the tissue is changing.
— What’s your move? Read on.
Before you read
- What must be done before, during, and after antivenom?
- When is it safe to observe, and when is this an ICU problem?
When to Think of It
Think venomous snakebite when there is progressive pain, swelling, ecchymosis, fang marks, nausea/vomiting, paresthesias, bleeding, or systemic symptoms after a bite in the US. Copperheads usually cause prominent local injury; rattlesnakes are more likely to add hematologic and systemic toxicity; coral snakes classically cause neurotoxicity with minimal early local findings.
Sick or Not Sick
The fork is dry/minimal envenomation vs progressive envenomation/systemic toxicity. The single call that matters most is whether the patient needs antivenom now and monitored admission versus serial exams in observation.
The First Fifteen Minutes
- Remove constricting items, splint/immobilize the limb, and mark swelling margins immediately; this slows venom spread and lets you track progression.
- Elevate the limb to heart level for most cytotoxic pit viper bites; do not aggressively ice, cut, suck, or use routine tourniquets because they worsen tissue injury.
- Pain still severe → fentanyl 50–100 mcg IV q5–10 min PRN or hydromorphone 0.5–1 mg IV q10–15 min PRN, because adequate analgesia reduces catecholamine surge and allows serial exams.
- Nausea/vomiting → ondansetron 4–8 mg IV/PO, because emesis can worsen distress and complicate oral meds/monitoring.
- Progressive swelling, thrombocytopenia, abnormal fibrinogen, bleeding, systemic signs, or neurotoxicity → antivenom now:
- Crotalidae polyvalent immune Fab (CroFab) 4–6 vials IV initial dose infused per protocol, because Fab fragments neutralize circulating venom and halt progression.
- Anavip 10 vials IV initial dose is an alternative where used; check institutional availability and protocol, because dosing/retreatment schedules differ.
- Anaphylaxis/infusion reaction during antivenom → epinephrine 0.3–0.5 mg IM now plus standard resuscitation, because venom is not the only thing that can kill the patient.
- Hypotension/shock → 1–2 L isotonic crystalloid IV bolus, because venom-mediated vasodilation/capillary leak and allergic reactions can both drop perfusion.
Definitive Care & Disposition
Get labs at baseline and repeat: CBC, CMP, PT/INR, fibrinogen, CK, type and screen, and serial limb measurements. Poison center/toxicologist input is ideal. Admit for observation if there is any progression, need for antivenom, systemic symptoms, coagulopathy, or unreliable follow-up; ICU if shock, airway involvement, severe neurotoxicity, or major bleeding. True dry bites or clearly minor local-only bites may be observed with serial exams, but only if swelling is not progressing and labs remain reassuring. Tetanus update as indicated. Surgical consult is for compartment syndrome concern, but true compartment syndrome is uncommon and should not be assumed from swelling alone.
How This One Kills
The classic error is confusing venom-induced swelling for a “simple cellulitis” or, conversely, overcalling compartment syndrome and cutting early. The bigger lethal miss is failing to recognize evolving systemic envenomation or coagulopathy before bleeding or shock declares itself.
The Differential — What Else Looks Like This
- Cellulitis/abscess — slower onset without fang marks or evolving coagulopathy; confusing it delays antivenom and serial labs.
- Necrotizing soft tissue infection — pain out of proportion and rapid swelling overlap, but fever, crepitus, skin anesthesia, and toxic appearance point away from envenomation; confusing it can send the patient to unnecessary surgery instead of antivenom.
- Allergic reaction/anaphylaxis — urticaria, wheeze, and hypotension can occur after the bite or antivenom; confusing the source of shock changes treatment priorities.
- Compartment syndrome — tense compartments and pain with passive stretch may appear, but snakebite swelling alone often does not require fasciotomy; confusing it leads to harmful surgery.
The Second-Day Story
Elderly patients, intoxicated patients, and those with delayed presentation may under-report the bite pain and local swelling, or present first with bleeding, weakness, or syncope rather than a dramatic wound. Copperhead bites can look deceptively “benign” at the scene and then swell significantly over hours, while coral snake bites may have minimal early local findings but rising neuromuscular weakness later. When the story is murky, serial exams and repeat coagulation studies matter more than the initial look.
Back to Our Patient
Back to our 42-year-old hiker with the swollen ankle and trailhead tourniquet: he has progressive pain and expanding edema after a likely pit viper bite, so this is not a dry bite. We remove the tourniquet, splint and mark the leg, give IV analgesia, send baseline labs including fibrinogen and platelets, and call poison control. Because his swelling is advancing, he gets antivenom now, with close monitoring for infusion reaction and repeat exams/labs to see if the envenomation is halted. He is admitted for serial reassessment and further antivenom if needed.
Patient Presentation to Attending
How you’d present this patient on the floor — tight, pertinent positives and negatives, no rambling
“This is a 42-year-old man with a probable snakebite to the left ankle while hiking, now with rapidly progressive pain and swelling up the leg. He has two puncture wounds, worsening edema over serial marks, nausea, and tingling but no syncope or airway symptoms; he did have a tourniquet applied prehospital. On exam he’s hemodynamically stable, the leg is tender and swollen without crepitus, and I don’t see urticaria or wheeze. I’m concerned for evolving pit viper envenomation rather than a dry bite or cellulitis. I’ve removed the constriction, splinted the limb, started analgesia, drawn CBC/CMP/PT-INR/fibrinogen, and called poison center. Because the swelling is progressing, I think he needs CroFab now and admission for serial neurovascular checks and repeat labs.”
Study Directive
- Draw a US snakebite algorithm from memory: local only vs systemic/coagulopathic vs neurotoxic.
- Memorize the first-line ED actions in order: remove constriction, immobilize, mark swelling, labs, poison center, antivenom if progression.
- Practice distinguishing copperhead, rattlesnake, and coral snake patterns in 60 seconds.
- Rehearse a 30-second oral presentation including whether the bite is dry, progressive, or systemic.
- Look up your institution’s CroFab/Anavip pathway and write down retreatment triggers.
Recent Literature
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Review or guideline Snake Envenomation
High-yield reference for ED management of snake envenomation, including serial exams/labs, antivenom indications and dosing, coagulopathy monitoring, and avoidance of harmful first-aid measures.