Eduovisual
Emergency & Toxicology
Bites and stings: snakes, spiders, marine animals
— ~7,000–8,000 venomous snakebites/year (95% pit vipers: rattlesnakes, copperheads, cottonmouths); ~5 deaths/year
— Black widow and brown recluse spider envenomations cluster regionally (widows nationwide; recluses in south-central US)
— Marine envenomations: jellyfish, stingrays, Portuguese man-of-war (Atlantic/Gulf), stonefish/lionfish (Pacific, aquariums)
— Sudden severe pain at an extremity after outdoor/water exposure, especially with rapidly progressing edema, ecchymosis, or hemorrhagic bullae → pit viper
— Generalized muscle cramping, abdominal rigidity mimicking peritonitis, hypertension, diaphoresis hours after a minor bite → black widow (latrodectism)
— Painless or mildly painful bite evolving into a necrotic ulcer with red-white-blue sign over 24–72 h → brown recluse (loxoscelism)
— Linear urticarial welts after ocean swim → jellyfish; deep puncture of foot in surf zone with disproportionate pain → stingray
— Distinguish dry bite (~25% of pit viper bites) from envenomation — must observe ≥8 h before clearance
— Identify neurotoxic vs hemotoxic/cytotoxic syndromes; Mojave rattlesnake and coral snake cause neurotoxicity; most North American pit vipers cause local tissue injury and coagulopathy
— Coral snake mnemonic: "Red on yellow, kill a fellow; red on black, venom lack" (US species only)
Board pearl: On Step 3, the highest-yield decision is not identifying the snake species but recognizing progression of swelling, coagulopathy, or systemic toxicity — these mandate antivenom regardless of species. Marking the leading edge of swelling with a pen and time-stamping every 15–30 minutes is a CCS-friendly order that demonstrates appropriate monitoring and triggers escalation when progression occurs.
— Time of bite, geographic location, snake description (triangular head, elliptical pupils, rattle, banding pattern), single vs multiple strikes
— Prehospital interventions to undo: tourniquets, ice, incision/suction, electric shock, alcohol — all harmful
— Tetanus status, anticoagulant use, prior antivenom exposure (risk of serum sickness/anaphylaxis on re-treatment)
— Immediate burning pain, fang marks, progressive edema, ecchymosis, hemorrhagic blebs
— Systemic: nausea, perioral paresthesias, metallic taste, fasciculations (Mojave/Timber → neurotoxicity)
— Labs: thrombocytopenia, hypofibrinogenemia, ↑PT/INR — "venom-induced consumptive coagulopathy"
— Minimal local findings; delayed (up to 12 h) descending flaccid paralysis, cranial neuropathies, respiratory failure
— Pinprick bite → target lesion → diffuse painful cramping (back, abdomen, chest), hypertension, tachycardia, diaphoresis, priapism; board mimic of acute abdomen or MI
— Initially painless; 24–72 h later central necrosis with surrounding pallor and erythema (red-white-blue); rare systemic loxoscelism with hemolysis, DIC, AKI (more common in children)
— Jellyfish/man-of-war: linear erythematous welts, immediate burning
— Stingray: puncture wound, often dorsum of foot, severe pain disproportionate to wound, retained spine
— Stonefish/scorpionfish: excruciating pain, systemic toxicity
— Sea urchin: retained spines, granulomatous reaction
Key distinction: Black widow = painful cramping without necrosis; brown recluse = necrotic ulcer without cramping. Confusing them on a Step 3 stem leads to wrong management (antivenom + opioids/benzos vs wound care).
— Hypotension, tachycardia → systemic envenomation, anaphylactoid response, or hemorrhage from coagulopathy
— Hypertension with diaphoresis → latrodectism (catecholamine surge)
— Bradycardia, hypoventilation, ptosis, dysarthria → coral snake or Mojave neurotoxicity (imminent respiratory failure)
— One or two fang punctures (vs scratches in nonvenomous colubrids)
— Measure and mark leading edge of edema/ecchymosis every 15–30 min with circumferential limb measurements at fixed landmarks
— Compartments: pain with passive stretch, tense compartment, paresthesias → consider compartment syndrome (rare; measure pressures before fasciotomy — most "tight" limbs improve with antivenom)
— Hemorrhagic bullae, oozing from puncture/IV sites, gingival bleeding → coagulopathy
— Target lesion at bite site, board-like abdominal rigidity without rebound, facial grimace (facies latrodectismica), HTN
— Central dusky/violaceous patch with halo of pallor and outer erythema; eschar formation; check for hemoglobinuria
— Tentacle remnants on skin (man-of-war/box jellyfish); fern-leaf pattern of welts
— Stingray wound: jagged laceration with retained barb; image to assess depth
— Serial cranial nerve assessment, single-breath count, negative inspiratory force for impending respiratory failure
Step 3 management: When examining a snakebitten limb, document circumference at three levels (above, at, below bite) in the chart at presentation and q30 min — this is the objective measure that triggers antivenom escalation. On CCS, order "serial limb measurements" alongside labs.
— CBC with platelets, PT/INR, aPTT, fibrinogen, D-dimer
— CMP (baseline renal/hepatic function), CK (rhabdomyolysis with rattlesnake), urinalysis for myoglobin/blood
— Type and screen if coagulopathy or bleeding
— Repeat labs at 0, 4–6, 12, 24 h, then daily; coagulopathy can recur 2–14 days after initial control (late recurrent coagulopathy)
— Labs often normal; bedside spirometry, NIF, ABG if respiratory compromise; continuous SpO2 and capnography
— Generally no specific labs; check CK if severe cramping; ECG for tachydysrhythmia; troponin if chest pain to rule out demand ischemia (common board distractor)
— Most need only wound care, but obtain CBC, retic, LDH, haptoglobin, bilirubin, BMP, UA, coags if systemic symptoms or pediatric patient (loxoscelism with hemolysis/DIC/AKI)
— DAT (Coombs) often positive in immune-mediated hemolysis
— Stingray wound: plain radiograph or ultrasound to identify retained radiopaque spine fragments; consider CT if deep penetration of trunk
— Tetanus and rabies risk assessment (rabies not from marine animals, but consider for terrestrial bites)
— ECG if hypertensive/tachycardic, elderly, or known CAD
— Pregnancy test in reproductive-age females (affects antivenom decision-making, though antivenom is not contraindicated)
Board pearl: Recurrent coagulopathy after CroFab is a classic Step 3 vignette — patient discharged day 3, returns day 7 with bruising and INR 3.5. Outpatient INR, platelets, and fibrinogen at 2–3 day intervals for 2 weeks after rattlesnake envenomation are standard discharge orders.
— Photographs are safer than capture; never bring a live snake to the ED
— Bedside venom detection kits are used in Australia, not in the US
— In US, treat the syndrome, not the species; antivenom is polyvalent for pit vipers
— Indicated when limb is tense, pain disproportionate, paresthesias persist despite antivenom
— Threshold for fasciotomy: compartment pressure >30 mmHg AND inadequate response to additional antivenom
— Most cases of "compartment-like" swelling resolve with antivenom alone — fasciotomy worsens outcomes when done reflexively
— Stingray spine: radiograph + bedside US; MRI if osteomyelitis suspected later
— Sea urchin spines: US is the modality of choice for radiolucent calcium carbonate spines
— Differential includes acute abdomen, MI, pheochromocytoma — obtain troponin, lipase, abdominal imaging selectively before committing to envenomation diagnosis if history ambiguous
— No reliable confirmatory test (ELISA exists but not clinically deployed in US)
— Diagnosis is clinical + exposure history + lesion evolution
— Stonefish/scorpionfish: clinical diagnosis; antivenom available in Australia for stonefish
— Box jellyfish (Chironex fleckeri) — Indo-Pacific; CSL antivenom in endemic regions; not relevant to US waters but Step 3–quizzable
Key distinction: A necrotic skin lesion attributed to "spider bite" in a region where brown recluses don't live (e.g., New England) is far more likely MRSA. Step 3 favors wound culture and empiric MRSA coverage over presumptive loxoscelism in non-endemic areas — overdiagnosis of recluse bites is a well-documented patient safety issue.
— Minimal: local swelling <10 cm, no systemic symptoms, normal labs
— Moderate: swelling beyond bite site, mild systemic symptoms, mildly abnormal coags
— Severe: rapidly progressing swelling crossing a major joint, hemodynamic instability, marked coagulopathy, neurotoxicity
— Remove rings, watches, constrictive clothing
— Immobilize limb at heart level (not elevated, not dependent)
— IV access in unaffected limb, normal saline, analgesia (opioids; avoid NSAIDs and aspirin due to coagulopathy)
— Update tetanus
— Do NOT: incise, suction, apply ice, tourniquet, electric shock, or give prophylactic antibiotics (infection rate <3%)
— Observe asymptomatic patients ≥8 hours with serial exams and labs; if all normal at 8 h, discharge with return precautions
— Mild–moderate: opioids + benzodiazepines for cramping; muscle relaxants
— Severe (refractory pain, pregnancy with threatened miscarriage, hypertensive crisis): Latrodectus antivenom (equine; risk of anaphylaxis and serum sickness — informed consent required)
— Local wound care, elevation, analgesia, tetanus
— No proven role for dapsone, steroids, or hyperbaric oxygen in routine cases (Step 3 distractors)
— Delayed surgical debridement only after eschar fully demarcates (often weeks)
— Heat (45°C × 30–90 min) denatures protein venom: stingray, stonefish, sea urchin, lionfish, weeverfish, catfish
— Vinegar (5% acetic acid) to inactivate nematocysts: box jellyfish, man-of-war (controversial for Portuguese man-of-war — some recommend seawater rinse instead)
— Remove visible tentacles with forceps; do not rub with sand or rinse with fresh water (triggers nematocyst discharge)
Step 3 management: "Hot for spines, vinegar for stings" is the high-yield decision rule. On CCS, immersing a stingray foot wound in hot water before imaging is the correct first order.
— Indicated for any progression of swelling, systemic toxicity, or hematologic abnormality
— Initial: 4–6 vials IV over 60 min; reassess at 1 h; redose 4–6 vials until "initial control" (arrest of progression, resolution of systemic symptoms, normalization of coags)
— Then maintenance: 2 vials q6h × 3 doses to prevent recurrence
— Adverse: anaphylaxis (1–8%), serum sickness (rare); pretreatment with antihistamines/steroids not routine
— Longer half-life, lower rate of recurrent coagulopathy; loading dose 10 vials; no scheduled maintenance
— Preferred in many centers for rattlesnake bites
— Limited supply; give empirically if confirmed coral snake exposure even before symptoms (neurotoxicity is delayed and irreversible once established)
— Supportive care + mechanical ventilation may be required
— Equine-derived; one vial IV diluted in 50 mL NS over 30 min
— Reserve for severe latrodectism, pregnancy with preterm labor, or refractory pain
— Test dose not required, but anaphylaxis risk real — have epinephrine ready
— Analgesia: opioids preferred; avoid NSAIDs/aspirin in pit viper bites (coagulopathy)
— Benzodiazepines: muscle relaxation in latrodectism
— Tetanus toxoid ± immune globulin per status
— Antibiotics not routine; reserve for clinical infection. Marine wounds: cover Vibrio (doxycycline + ceftriaxone) for stingray/coral injuries in immunocompromised or significant wounds
— Insufficient evidence; not recommended on boards
Board pearl: Antivenom is dosed by clinical effect, not patient weight — pediatric doses equal adult doses. Withholding antivenom in a child "because of size" is a wrong-answer trap.
— Clean with soap and water; do not close primarily; loose dressing
— Mark and measure edema; elevate limb to heart level once antivenom started, then above heart after control
— Fasciotomy only if measured compartment pressure >30 mmHg AND failure of additional antivenom — true compartment syndrome is rare
— Hot water immersion 45°C × 30–90 min (denatures heat-labile venom; provides analgesia)
— Local anesthetic infiltration or regional block
— Explore wound under anesthesia; remove all spine fragments and integument sheath (causes ongoing envenomation and infection)
— Irrigate copiously; leave open for delayed primary closure
— Imaging (XR/US) post-removal to confirm no retained foreign body
— Antibiotic prophylaxis for marine wounds: fluoroquinolone or doxycycline + cephalosporin to cover Vibrio, Aeromonas, Pseudomonas, staph/strep
— Rinse with seawater or vinegar (acetic acid 5%); do NOT use fresh water (osmotic nematocyst discharge)
— Remove tentacles with forceps; apply shaving cream and scrape with credit card edge
— Hot water immersion (45°C) for pain
— Topical lidocaine; oral analgesics
— Conservative: cleansing, elevation, analgesia, tetanus
— Delayed debridement after eschar demarcation (typically 2–6 weeks)
— Early surgical excision is harmful (high recurrence, poor cosmesis)
— Coral snake or Mojave rattlesnake: prepare for early intubation at first sign of bulbar weakness or hypoventilation
— Mechanical ventilation may be required for days while paralysis resolves
CCS pearl: For a stingray foot wound — order "hot water immersion 45°C," "radiograph foot," "wound exploration under local anesthesia," "tetanus toxoid," and "ciprofloxacin PO" as a clustered set of actions; this maps to the standard ED workflow and avoids penalty for missing steps.
— Higher baseline anticoagulation use (DOACs, warfarin, antiplatelets) compounds venom-induced coagulopathy → lower threshold for antivenom and transfusion
— Reduced physiologic reserve: monitor closely for hypotension during antivenom infusion
— Comorbid CAD: latrodectism-induced HTN/tachycardia can precipitate ACS — obtain ECG and troponin
— Polypharmacy: opioid dosing adjustments; avoid NSAIDs entirely
— Serum sickness from antivenom may present atypically (low-grade fever, malaise mistaken for "post-hospital weakness")
— CroFab and Anavip cleared renally; no dose adjustment needed (dose by clinical effect)
— Rhabdomyolysis from rattlesnake bite + AKI: aggressive IVF, monitor CK, urine output, K+
— Adjust adjunctive medications: opioids (morphine metabolites accumulate — prefer hydromorphone or fentanyl in CKD/ESRD), avoid NSAIDs
— Doxycycline preferred over fluoroquinolones in some renal patients for marine wound prophylaxis (no renal adjustment for doxy)
— Coagulopathy at baseline magnifies venom effects; check baseline INR
— Acetaminophen for adjunctive analgesia: cap at 2 g/day in cirrhosis
— Benzodiazepines for latrodectism: prefer lorazepam or oxazepam (no hepatic phase I metabolism)
— Prior horse-serum exposure (Latrodectus antivenom, coral snake antivenom) increases anaphylaxis and serum sickness risk — document on the chart and counsel for life
— CroFab/Anavip are ovine Fab/F(ab')2 fragments — different antigen exposure than equine products
Step 3 management: In an elderly patient on apixaban with a rattlesnake bite and INR 1.4 but progressing swelling, start antivenom early and hold apixaban; do not wait for severe coagulopathy. Document medication reconciliation and provide bridging plan at discharge.
— Snake envenomation in pregnancy: fetal loss rate up to 30% with severe envenomation, primarily from maternal hypotension, hypoxia, or DIC
— Antivenom is not contraindicated — benefit far outweighs risk; withholding causes fetal demise more often than antivenom does
— Continuous fetal monitoring in viable pregnancies (≥23 weeks); OB consultation
— Latrodectism in pregnancy: severe abdominal cramping can be mistaken for abruption or preterm labor — perform OB exam, ultrasound; antivenom indicated for severe cases or threatened miscarriage
— Avoid NSAIDs (third trimester especially), tetracyclines (doxycycline) — use azithromycin or cephalosporins for marine wound prophylaxis
— Children receive the same antivenom dose as adults (venom load is fixed; child has less body mass to buffer it)
— Higher risk of severe envenomation per kg of venom
— Systemic loxoscelism is more common in children than adults: hemolytic anemia, hemoglobinuria, DIC, AKI — admit and monitor with serial CBC, UA, BMP, coags
— Pain assessment with age-appropriate scales (FACES, FLACC)
— Marine envenomations: hot water immersion temperatures must be measured (45°C) to avoid burns — never use "as hot as tolerable" with children
— Risk-taking behavior (handling captive exotic snakes, "rough-scaled" bites from pet venomous species) — exotic antivenom may need to be sourced through poison control/zoos
— Address substance use; alcohol intoxication delays presentation
Board pearl: Vignette of pregnant woman with rattlesnake bite — the answer is give antivenom AND monitor fetus, never "delay antivenom because pregnant." This is the single most common Step 3 trap in this topic.
— Venom-induced consumptive coagulopathy (VICC): hypofibrinogenemia, ↑INR, thrombocytopenia → mucosal bleeding, intracranial hemorrhage (rare but devastating)
— Recurrent coagulopathy after CroFab discharge (days 5–14): obtain outpatient INR, fibrinogen, platelets twice weekly × 2 weeks; readmit and redose antivenom if severe
— Tissue necrosis, chronic wound, functional impairment — physical therapy referral
— True compartment syndrome (rare) — fasciotomy if pressure >30 mmHg despite antivenom
— Rhabdomyolysis → AKI
— Serum sickness 7–21 days after antivenom: fever, urticaria, arthralgias, lymphadenopathy → oral steroids, antihistamines
— Anaphylaxis during infusion: stop, epinephrine, restart slowly after stabilization
— Hypertensive emergency, MI, stroke; priapism; rhabdomyolysis
— Prolonged cramping/pain syndromes lasting days
— Pregnancy: spontaneous abortion, preterm labor
— Local: deep necrosis, secondary bacterial infection, scarring
— Systemic loxoscelism (pediatric predominant): hemolytic anemia, DIC, AKI, rarely death
— Retained foreign body → granuloma, chronic infection, osteomyelitis
— Vibrio vulnificus sepsis in immunocompromised/cirrhotic patients with stingray or marine wounds — hemorrhagic bullae, septic shock, 50% mortality
— Stonefish: cardiovascular collapse, hypotension
— Sea urchin granuloma — delayed inflammatory nodule
— Unnecessary fasciotomy
— Prophylactic antibiotics → C. difficile, resistance
— Tourniquet → limb ischemia
— Ice → frostbite over already-injured tissue
Key distinction: Recurrent coagulopathy is asymptomatic in most cases — patients may have INR >5 with no bleeding. Discharge instructions must include outpatient labs, not just "return if bleeding." This is a transitions-of-care pitfall Step 3 loves.
— Hemodynamic instability requiring vasopressors
— Respiratory compromise (coral snake, Mojave rattlesnake neurotoxicity)
— Severe coagulopathy with active bleeding or ICH
— Compartment syndrome
— Anaphylaxis to antivenom requiring ongoing vasoactive support
— Severe rhabdomyolysis with AKI
— Any envenomation requiring antivenom maintenance dosing
— Progressing swelling without systemic toxicity
— Pediatric patients with any envenomation (lower threshold)
— Pregnant patients (fetal monitoring)
— Suspected dry bite with normal serial exams and labs
— Mild local symptoms only, no progression
— Poison Control (1-800-222-1222) — call early on every envenomation; they coordinate antivenom sourcing, dosing, and toxicologist input
— Toxicology service if available
— Hand surgery / orthopedics for compartment concerns
— Hematology for refractory coagulopathy
— OB for pregnant patients
— Infectious disease for complicated marine wounds, immunocompromised
— Plastic surgery for late brown recluse wound management
— Local hospital lacks antivenom stock → transfer to tertiary center; start antivenom before transfer if available — never delay for transport
— Exotic snake bite (zoo, pet trade) requires species-specific antivenom often stocked only at zoos or referral centers
— Asymptomatic at 8–12 h with normal repeat labs, normal exam, marked edema not advancing
— Reliable follow-up arranged
— Clear written return precautions
CCS pearl: Contact poison control early on every envenomation case — on Step 3 CCS, ordering "consult Poison Control" is rewarded and helps coordinate antivenom logistics, which is otherwise an easy item to forget.
— Dry bite (~25%): fang marks without venom delivery; observe 8–12 h with serial labs; discharge if no progression
— Nonvenomous snake bite: multiple small puncture marks (rows of teeth), no fang punctures, no progression — wound care and tetanus only
— Pit viper vs coral snake: local tissue injury vs delayed neurotoxicity with minimal local signs; mnemonic for coral snake coloring (red-on-yellow)
— Exotic/imported snake (pet trade, zoo): mamba, cobra, krait, viper — call poison control for species-specific antivenom sourcing
— Black widow vs brown recluse: cramping/HTN without necrosis vs painless necrotic ulcer
— Hobo spider, wolf spider, tarantula: largely benign in US; local reactions only — reassurance, wound care
— Many "spider bites" are misattributed — bedbug bites, cellulitis, MRSA abscess, herpes zoster, pyoderma gangrenosum, vasculitis can mimic
— Jellyfish vs man-of-war: similar linear welts; treatment overlaps but man-of-war may worsen with vinegar in some regions
— Stingray vs stonefish/lionfish: all heat-treated; stonefish has specific antivenom (not US-relevant)
— Sea urchin vs starfish (crown-of-thorns): both retained spines; sea urchin spines are calcium carbonate (radiolucent); imaging with US
— Sea snake (Indo-Pacific): neurotoxic, like elapids; antivenom available regionally
— Cone snail: paralytic envenomation; supportive care, no antivenom
— Bee/wasp/hornet stings: anaphylaxis is the main concern, not envenomation per se — epinephrine, antihistamines, observation
Board pearl: A patient in Boston with a "necrotic spider bite" almost certainly has MRSA or another cause, not loxoscelism — brown recluses do not live in New England. Geographic plausibility is a Step 3 favorite.
— Cellulitis/necrotizing fasciitis: fever, leukocytosis, gas in tissue (NF); often more diffuse, lacks coagulopathy
— Deep vein thrombosis: unilateral leg swelling without puncture marks, no labs derangement of venom type
— Compartment syndrome from trauma: history of crush, no envenomation signs
— Anticoagulant overdose: coagulopathy without local tissue findings
— Acute abdomen (appendicitis, perforation, pancreatitis): rebound tenderness, fever, abnormal labs/imaging
— MI: chest pain, ECG changes, ↑troponin; latrodectism can also raise troponin from demand ischemia
— Tetanus: opisthotonos, trismus, no bite history needed; unimmunized
— Pheochromocytoma: paroxysmal HTN, headache, palpitations
— Sympathomimetic toxidrome (cocaine, amphetamine): hyperthermia, mydriasis, recent use
— Black widow bite is sometimes missed: in cramping abdominal pain with HTN and diaphoresis, ask about bite
— MRSA abscess: fluctuant, purulent — I&D and culture
— Pyoderma gangrenosum: associated with IBD, RA; pathergy; treatment is steroids, NOT debridement
— Vasculitis (ANCA-associated, cryoglobulinemia)
— Cutaneous anthrax: painless ulcer with eschar, occupational exposure
— Tularemia, sporotrichosis, atypical mycobacteria
— Calciphylaxis in ESRD patients
— Diabetic ulcer, pressure injury, factitial
— Coral abrasion: stinging cell exposure, similar to mild jellyfish
— Seabather's eruption ("sea lice"): trapped jellyfish larvae under swimsuit
— Cercarial dermatitis ("swimmer's itch"): freshwater schistosome larvae
— Vibrio cellulitis from raw seafood handling
Key distinction: Pyoderma gangrenosum worsens with debridement (pathergy). If a "brown recluse bite" expands after surgical intervention, especially in an IBD patient, switch to steroids and dermatology consult — not more cutting.
— Outpatient INR, fibrinogen, platelets at days 2–3, 5, and 7 post-discharge for pit viper envenomations (especially rattlesnake) to catch recurrent coagulopathy
— Avoid elective procedures, contact sports, dental work, and NSAIDs/aspirin for 2 weeks after envenomation
— Resume chronic anticoagulants only after coags normal and bleeding risk reassessed; discuss with prescribing clinician
— Return precautions: new bruising, oozing gums, hematuria, melena, severe headache (ICH)
— Wound check at 24–48 h; PT/OT referral for functional recovery
— Symptoms can recur for days — oral opioid + benzodiazepine + muscle relaxant taper
— Return for chest pain, severe HTN, recurrent cramping
— Wound care instructions, daily cleansing, dressing changes
— Outpatient follow-up at 48–72 h, then weekly until healed
— Surgical referral if eschar formation for delayed debridement (weeks)
— Photograph wound serially to track evolution
— Stingray wound: oral antibiotic (ciprofloxacin or doxycycline) 5–7 days; daily wound check; signs of Vibrio sepsis return precautions (rapidly spreading erythema, fever, hemorrhagic bullae)
— Sea urchin retained spines: outpatient surgical referral if symptomatic
— Snakes: closed-toe shoes, avoid tall grass and rocky outcrops, don't handle snakes (most bites are intentional handling), use flashlight at night
— Spiders: shake out clothing/shoes in endemic areas, clear woodpiles and clutter
— Marine: shuffle feet in surf zone (stingray shuffle), avoid touching unknown sea life, wear protective footwear
— Patients who had antivenom: medical alert documentation; future re-exposure increases serum sickness/anaphylaxis risk
Step 3 management: Repeat outpatient coagulation studies at days 2–3, 5, and 7 after pit viper envenomation is the single highest-yield discharge order — recurrent coagulopathy is asymptomatic until catastrophic bleeding.
— Pit viper: serial CBC, PT/INR, fibrinogen at 0, 6, 12, 24 h inpatient; outpatient days 2–3, 5, 7; weekly until normal × 2
— Coral snake: neurologic exam q1–2h × 24 h; respiratory parameters (NIF, VC, SpO2); discharge when neurologically stable × 24 h after symptom peak
— Latrodectism: pain scores, BP, HR q1h × 4 h post-antivenom; discharge when cramping controlled with oral meds
— Brown recluse: wound photographs and measurements at each visit; CBC/UA if systemic concern (especially children)
— Marine: wound exam, signs of infection or retained foreign body; recheck at 48–72 h
— Severe pit viper envenomation often leaves residual stiffness, weakness, decreased ROM
— Early PT/OT referral for hand/foot bites; functional recovery may take months
— Pain management plan for chronic neuropathic pain (gabapentin, duloxetine)
— PTSD and snake/spider phobia common after severe envenomation
— Screen for anxiety, sleep disturbance at follow-up; referral to mental health
— Provide written discharge instructions in primary language
— Specific return precautions: bleeding signs, expanding lesion, fever, new neurologic symptoms
— Document teach-back of key instructions in chart
— Coordinate with PCP within 1 week for medication reconciliation, lab follow-up
— Confirm patient can access labs and afford follow-up (cost barriers are common reason for missed recurrent coagulopathy detection)
— Document antivenom administration in problem list and allergy section for life (future serum sickness risk)
Board pearl: Document antivenom exposure permanently — equine-derived antivenoms (Latrodectus, coral snake) carry meaningful re-exposure anaphylaxis risk, and ovine products (CroFab/Anavip) can cross-react. This is a transitions-of-care safety item Step 3 examines.
— Risks: anaphylaxis (1–8%), serum sickness (5–10% delayed), cost (CroFab/Anavip can exceed $100,000 hospital bill); benefits: prevent limb loss, coagulopathy, death
— Obtain consent when feasible; in emergency with impaired capacity, implied consent under emergency exception applies
— Pregnant patients: counsel that withholding antivenom poses greater fetal risk than antivenom itself
— Competent patient may refuse antivenom; document capacity assessment, risks reviewed, voluntary refusal, against medical advice if leaving ED
— Provide harm-reduction instructions and clear return precautions
— Snake/spider bites generally not reportable, but exotic snake bites involving pet trade may trigger animal control or zoo notification
— Marine envenomations with Vibrio infection — Vibrio vulnificus is reportable in many states
— Pediatric envenomations from neglect (e.g., child sleeping on infested mattress, repeated brown recluse exposures) → consider child protective services if neglect suspected
— Recurrent coagulopathy after pit viper antivenom is the canonical transitions-of-care failure: patient discharged, lost to follow-up, presents with ICH. Mitigations:
— Schedule first outpatient lab draw before discharge
— Provide patient with written timeline of labs needed
— Direct communication with PCP (warm handoff or fax + phone call)
— Equip patient with explicit return precautions
— Antivenom cost is a known barrier and ethical pressure point — never withhold for cost in acute envenomation; involve social work and financial counseling post-stabilization
— Patients without insurance still receive antivenom under EMTALA stabilization requirements
— Diagnosing "brown recluse bite" without geographic plausibility or witnessed spider → may delay correct diagnosis (MRSA, vasculitis) and is a malpractice risk
— Always document objective findings (measurements, photographs)
Step 3 management: When discharging after rattlesnake antivenom, schedule the first follow-up lab draw and PCP appointment from the ED, not "tell the patient to follow up" — this closed-loop handoff is the safe-discharge standard.
— Pit vipers (rattlesnake, copperhead, cottonmouth) = hemotoxic/cytotoxic: local injury + coagulopathy
— Mojave rattlesnake + some Timber rattlesnakes = neurotoxic variant
— Coral snake = neurotoxic (elapid); descending paralysis, delayed onset
— "Red on yellow, kill a fellow" — US coral snake (does not apply to non-US species)
— ~25% of pit viper bites are dry bites
— Antivenom dose is by clinical effect, not weight
— Black widow (Latrodectus mactans) — α-latrotoxin → massive neurotransmitter release → muscle cramping, HTN
— Brown recluse (Loxosceles reclusa) — sphingomyelinase D → dermonecrosis ± systemic hemolysis
— "Violin" marking on brown recluse cephalothorax; 6 eyes (not 8)
— Hourglass marking on black widow ventral abdomen
— Stingray, stonefish, lionfish, catfish, weeverfish, sea urchin → hot water (45°C) immersion
— Jellyfish, man-of-war → vinegar (acetic acid 5%); do not use fresh water
— Box jellyfish (Chironex fleckeri) — Indo-Pacific, deadliest; CSL antivenom regionally
— Sea snake — neurotoxic elapid; rare in US
— Vibrio vulnificus — cirrhotic + marine wound = septic shock; doxy + ceftriaxone
— Avoid NSAIDs/aspirin in pit viper envenomation
— Avoid tetracyclines in pregnancy
— Watch for serum sickness 7–21 days post-antivenom
— Poison Control: 1-800-222-1222 (national)
Key distinction: Heat for spines, vinegar for stings — this single rule answers most marine envenomation Step 3 questions.
— Hiker with rattlesnake bite, swelling up to mid-calf at 1 h, INR 1.6, platelets 110K → Answer: CroFab/Anavip antivenom; distractors include fasciotomy, prophylactic antibiotics, ice
— Patient discharged day 3 after rattlesnake bite, returns day 8 with gum bleeding, bruising, INR 4 → Answer: recurrent coagulopathy, readmit, redose antivenom
— Patient with red-on-yellow snake bite, currently asymptomatic → Answer: administer antivenom empirically + admit for observation; do NOT wait for neurotoxicity
— Patient with severe abdominal cramping, board-like rigidity, HTN 190/110, no rebound, target lesion on thigh → Answer: opioid + benzodiazepine; antivenom if severe
— Necrotic skin lesion in New England, no spider seen → Answer: MRSA abscess; I&D and culture; empiric TMP-SMX or doxycycline
— Child from Missouri with necrotic lesion, dark urine, anemia → Answer: systemic loxoscelism; admit, supportive care, monitor for AKI/DIC
— Surfer with foot pain after stepping on stingray → Answer: hot water immersion 45°C, radiograph for retained spine, wound exploration, ciprofloxacin, tetanus
— Pregnant patient with rattlesnake bite, progressing swelling → Answer: antivenom + fetal monitoring; never withhold antivenom for pregnancy
— Cirrhotic shrimp handler with rapidly progressing bullous cellulitis, fever, hypotension → Answer: Vibrio vulnificus; doxycycline + ceftriaxone, urgent surgical debridement
— Linear welts after swim → Answer: rinse with vinegar, remove tentacles, hot water immersion, topical anesthetic; not fresh water
Board pearl: When a Step 3 stem describes a "spider bite" but never names the spider or describes the spider, suspect misattribution — the answer often involves MRSA, vasculitis, or another non-arachnid diagnosis.
The core teaching point: In envenomation emergencies, treat the syndrome, not the species — recognize the toxidrome (hemotoxic, neurotoxic, cytotoxic, or pain-predominant), apply the right antivenom or supportive measure (CroFab/Anavip for pit vipers; Latrodectus antivenom for severe widow bites; hot water for marine spines; vinegar for jellyfish), and never miss the transitions-of-care steps (serial outpatient labs for recurrent coagulopathy, antivenom documentation, return precautions).
Step 3 management: When in doubt, call Poison Control, mark the swelling, draw serial coags, and arrange closed-loop outpatient follow-up before discharge — these four actions cover the high-yield management of nearly every envenomation vignette on the exam.