Snake Bite Envenomation in Adults

Quick Reference

Key Diagnostic Priorities

• Serial examinations with documented swelling progression (mark and time)
• Coagulation panel: PT/INR, aPTT, fibrinogen (most sensitive)
• Full blood count: Hemolysis, thrombocytopenia
• Renal function and electrolytes: AKI monitoring
• Creatine kinase: Rhabdomyolysis (especially with myotoxic venoms)
• Type and screen: Anticipate transfusion needs
• 20-minute whole blood clotting test (20WBCT): Resource-limited settings

Emergency Treatment Algorithm

INITIAL ASSESSMENT (0-15 minutes)
├── Secure airway if neurotoxic signs present
├── Two large-bore IV cannulae (unaffected limb)
├── Remove jewelry, constrictive clothing
├── Immobilize affected limb at heart level
├── Document time of bite and snake identification
└── Mark swelling extent with time stamp

ASSESS ENVENOMATION SEVERITY
├── Dry bite (20-25%): Fang marks only, no progression → Observe 8-12h
├── Mild: Local swelling less than 2 joints, no systemic → Observe, reassess hourly
├── Moderate: Swelling beyond 1 joint, mild coagulopathy → ANTIVENOM
└── Severe: Systemic symptoms, significant coagulopathy → IMMEDIATE ANTIVENOM

ANTIVENOM ADMINISTRATION
├── Crotalid (Pit Viper): CroFab 4-6 vials or Anavip 10 vials IV
├── Coral Snake: North American Coral Snake Antivenom (if available)
├── Australian Elapid: Polyvalent or monovalent based on identification
└── Monitor for anaphylaxis, serum sickness

SUPPORTIVE CARE
├── Tetanus prophylaxis
├── Analgesia (opioids preferred; avoid NSAIDs)
├── Avoid anticoagulants, aspirin
└── Wound care (no incision, no suction)

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Overview

Snake bite envenomation represents a major global health challenge, classified by the World Health Organization as a Category A Neglected Tropical Disease. [1] Envenomation occurs when a venomous snake injects venom through specialized fangs during a defensive or predatory bite. The clinical severity depends on multiple factors including snake species, venom quantity injected, bite location, and patient characteristics. [2]

Understanding the taxonomy of venomous snakes is essential for predicting clinical syndromes and guiding antivenom selection. The three medically significant snake families are Elapidae (cobras, kraits, mambas, coral snakes, Australian venomous snakes), Viperidae (true vipers and pit vipers including rattlesnakes, copperheads, and cottonmouths), and Colubridae (a small subset with rear fangs capable of significant envenomation). [3]

Emergency management focuses on rapid assessment, appropriate first aid, timely antivenom administration, and supportive care. Importantly, 20-25% of venomous snake bites result in "dry bites" where no venom is injected, necessitating observation to differentiate from true envenomation. [4]

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Epidemiology

Global Burden

Snake bite envenomation affects approximately 5.4 million people annually worldwide, resulting in 1.8 to 2.7 million envenomations and 81,000 to 138,000 deaths per year. [1] The greatest burden falls on agricultural workers in tropical and subtropical regions of Africa, Asia, and Latin America. South Asia accounts for nearly half of global snake bite deaths, with India alone reporting an estimated 46,000 annual fatalities. [5]

Regional Incidence

Demographics and Risk Factors

Exam Detail: ### Exam-Relevant Epidemiology Points

• US Statistics: ~7,000-8,000 venomous bites annually; 98% are pit vipers (Crotalidae); only 5-10 deaths/year [6]
• Australia: Despite highly venomous fauna, excellent prehospital care and antivenom availability limit fatalities to 2-3/year [7]
• Antivenom Impact: Mortality reduced from ~20% to less than 1% in developed nations with antivenom access [4]
• Economic Burden: Significant disability from tissue necrosis, amputations; major economic impact in endemic regions

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Venomous Snake Taxonomy and Venom Characteristics

Family Elapidae (Neurotoxic Predominant)

Elapid snakes possess fixed front fangs and primarily neurotoxic venoms. Major genera include cobras (Naja), kraits (Bungarus), mambas (Dendroaspis), coral snakes (Micrurus, Micruroides), and all Australian venomous snakes (Pseudonaja, Oxyuranus, Notechis, Pseudechis). [3]

Elapid Venom Components:

Family Viperidae (Hemotoxic/Cytotoxic Predominant)

Viperids possess retractable solenoglyphous fangs enabling deep venom injection. Divided into true vipers (Viperinae: Old World) and pit vipers (Crotalinae: primarily New World, also Asian). [8]

Subfamily Crotalinae (Pit Vipers):

Subfamily Viperinae (True Vipers):

Crotalid Venom Components:

Family Colubridae (Rear-Fanged Snakes)

Most colubrids are non-venomous or possess mild venoms insufficient to harm humans. However, some species cause significant envenomation: [3]

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Pathophysiology of Envenomation

Venom Delivery and Distribution

Snake venom is delivered through specialized fangs under muscular control, allowing snakes to regulate venom quantity. Approximately 20-25% of defensive bites are "dry bites" with no venom injection. [4] Following subcutaneous or intramuscular injection, venom spreads via lymphatic channels (primary route) and direct tissue diffusion. [9]

Envenomation Syndromes

Exam Detail: #### Syndrome 1: Local Tissue Effects (Cytotoxic)

Mechanism:

Venom injection (subcutaneous/IM)
         ↓
Metalloproteinases → Basement membrane degradation
         ↓
Phospholipases A2 → Cell membrane lysis
         ↓
Increased vascular permeability + Direct tissue destruction
         ↓
Edema, hemorrhage, necrosis

Predominant in: Pit vipers, puff adders, some cobras

Clinical Features:

• Progressive pain and swelling (begins within minutes)
• Ecchymosis, hemorrhagic bullae
• Tissue necrosis (may progress over days)
• Compartment syndrome (rare with adequate antivenom)

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Syndrome 2: Venom-Induced Consumptive Coagulopathy (VICC)

Mechanism:

Procoagulant toxins (thrombin-like enzymes, prothrombin activators)
         ↓
Activation of coagulation cascade
         ↓
Consumption of fibrinogen, factors V, VIII
         ↓
Secondary fibrinolysis
         ↓
Incoagulable blood, hemorrhage

Predominant in: Australian elapids, Russell's viper, saw-scaled vipers, many pit vipers

Laboratory Features:

• Prolonged PT/INR, aPTT (often unmeasurable)
• Undetectable or extremely low fibrinogen (less than 0.5 g/L)
• Elevated D-dimer, fibrin degradation products
• Thrombocytopenia (variable)

Clinical Features:

• Bleeding from puncture sites, gums, mucous membranes
• Hematuria, hematemesis, melena
• Intracranial hemorrhage (rare but devastating)

Key Concept - VICC vs DIC: VICC is venom-mediated consumptive coagulopathy with specific antivenom responsiveness. Unlike septic DIC, factor replacement alone is ineffective without antivenom neutralization of circulating venom. [10]

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Syndrome 3: Neurotoxicity

Postsynaptic Neurotoxicity:

Alpha-neurotoxins (elapid venoms)
         ↓
Competitive blockade at postsynaptic nicotinic AChR
         ↓
Descending flaccid paralysis (cranial → respiratory → peripheral)
         ↓
Respiratory failure

• Reversible with antivenom if given before toxin internalization
• Anticholinesterases (neostigmine) may provide temporary benefit
• Full recovery expected with supportive care

Presynaptic Neurotoxicity:

Presynaptic toxins (phospholipases A2)
         ↓
Destruction of presynaptic nerve terminals
         ↓
Depletion of acetylcholine vesicles
         ↓
Irreversible neuromuscular blockade at that synapse
         ↓
Prolonged paralysis (days to weeks)

• Limited antivenom efficacy once toxins internalized
• Anticholinesterases ineffective
• Requires prolonged mechanical ventilation
• Recovery depends on nerve terminal regeneration

Predominant in: Kraits (presynaptic), mambas (mixed), coral snakes, taipans, death adders

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Syndrome 4: Myotoxicity (Rhabdomyolysis)

Mechanism:

Myotoxic phospholipases A2
         ↓
Skeletal muscle membrane destruction
         ↓
Myoglobin release, CK elevation
         ↓
Myoglobinuric acute kidney injury

Predominant in: Sea snakes, Australian elapids (tiger snake, mulga snake), some rattlesnakes

Clinical Features:

• Muscle pain, tenderness, weakness
• Dark urine (myoglobinuria)
• Markedly elevated CK (> 10,000 U/L)
• Acute kidney injury
• Hyperkalemia

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Syndrome 5: Nephrotoxicity

Mechanisms:

• Direct nephrotoxin effects (Russell's viper)
• Myoglobinuric AKI
• Hemoglobinuric AKI (intravascular hemolysis)
• Hypoperfusion from hypovolemia/shock

Predominant in: Russell's viper (direct), sea snakes, Australian elapids

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Syndrome 6: Cardiovascular Toxicity

Mechanisms:

• Direct cardiotoxins (some cobras)
• Hypovolemic shock (third-spacing, hemorrhage)
• Anaphylactoid reactions to venom
• Vasodilation from vasoactive components

Dry Bites

Approximately 20-25% of venomous snake bites result in no envenomation ("dry bite"). [4] Snakes can control venom delivery and may bite defensively without injecting venom to conserve their hunting resources. Dry bites present with fang marks but no progressive symptoms or laboratory abnormalities. Diagnosis requires observation over 8-12 hours, as envenomation may have delayed onset.

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Clinical Presentation

Pit Viper Envenomation (Crotalidae)

Local Effects

Swelling Progression Documentation:

• Mark leading edge of swelling every 15-30 minutes initially
• Measure limb circumference at standardized points
• Progression beyond one joint = moderate envenomation
• Rapid progression = severe envenomation

Systemic Effects

Severity Grading

Elapid Envenomation

Coral Snake (Americas)

Critical Point: Coral snakes have delayed symptom onset. Patients with confirmed bites should be admitted for 24-hour observation regardless of initial symptom status. [11]

Cobra and Krait Envenomation (Asia/Africa)

Cobra (Naja spp.):

• More pronounced local effects than other elapids
• Spitting cobras cause severe ophthalmia
• Cardiotoxicity in some species
• Neurotoxicity develops over hours

Krait (Bungarus spp.):

• Minimal local effects (often painless bite)
• Delayed severe neurotoxicity (presynaptic predominant)
• Abdominal pain common
• High mortality if untreated

Australian Elapid Envenomation

Australian snakes present unique challenges with multiple simultaneous syndromes: [7]

Key Concept: Australian snake venom may cause profound coagulopathy with minimal local signs. The 20-minute whole blood clotting test (20WBCT) is valuable for rapid assessment in field settings.

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Differential Diagnosis

Conditions Mimicking Snake Bite

Snake Bite Without Identification

When snake identification is uncertain, base initial assessment on:

1. Geographic likelihood of venomous species
2. Bite characteristics (fang marks, local effects)
3. Symptom evolution over time
4. Laboratory abnormalities (coagulopathy, CK elevation)

In Australia: Venom detection kit (VDK) from bite site swab or urine can guide monovalent antivenom selection. [12]

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Diagnostic Approach

History

Essential Information:

• Time of bite (crucial for symptom progression)
• Circumstances (geographic location, activity)
• Snake description if observed (do NOT attempt to catch)
• Photograph if safely obtained
• First aid measures applied (note if tourniquet used)
• Symptoms since bite (progression, timing)
• Allergies (to antivenoms, horse/sheep proteins)
• Medications (anticoagulants, antiplatelets)
• Tetanus immunization status

Physical Examination

Systematic Assessment:

Swelling Documentation Protocol:

1. Mark leading edge with indelible marker and time
2. Measure circumference at:
   • 10 cm proximal to bite
   • Bite site level
   • 10 cm distal to bite
3. Repeat every 15-30 minutes initially, then hourly
4. Document any proximal progression

Laboratory Investigations

20-Minute Whole Blood Clotting Test (20WBCT):

• Place 2-3 mL venous blood in clean glass tube
• Leave undisturbed at room temperature for 20 minutes
• Tilt gently - if blood remains liquid, coagulopathy present
• Sensitivity ~90% for significant coagulopathy
• Useful in resource-limited settings [13]

Snake Identification

Do NOT attempt to capture the snake. If safely possible, photograph from distance.

Pit Viper Identification:

• Triangular head
• Vertical "cat-eye" pupils
• Heat-sensing pit between eye and nostril
• Rattles (rattlesnakes only)
• Keeled scales

Coral Snake Identification (North America):

• Red, yellow, and black bands encircling body
• Mnemonic: "Red on yellow, kill a fellow; red on black, venom lack" (applies only to North American species)
• Small, rounded head (not triangular)
• Black nose

Elapid vs Viperid General Features:

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First Aid Management

Evidence-Based First Aid

Clinical Pearl: The primary goal of first aid is to delay venom absorption while facilitating rapid transport to medical care.

Recommended Actions

Pressure Immobilization Technique (Australian Protocol)

The pressure immobilization technique (PIT) is specifically recommended for Australian elapid bites and may be considered for neurotoxic elapid bites elsewhere. It is NOT recommended for cytotoxic vipers (pit vipers, puff adders) due to risk of worsening local tissue damage. [14]

Technique:

1. Apply broad elastic bandage (10-15 cm width) starting at bite site
2. Wrap firmly (as tight as for sprained ankle) toward trunk
3. Then wrap from bite site distally to cover entire limb
4. Immobilize limb with splint
5. Target pressure: 40-70 mmHg (firm but fingers can slide under bandage)

Contraindications to PIT:

• Cytotoxic envenomation (pit vipers, puff adders)
• Already delayed presentation (> 2 hours)
• Significant local swelling already present

Harmful Interventions to Avoid

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Hospital Management

Initial Emergency Department Management

Immediate Actions (First 15 Minutes):

1. Airway assessment - Prepare for intubation if neurotoxic signs
2. IV access - Two large-bore cannulae in unaffected limb
3. Monitoring - Continuous ECG, SpO2, BP
4. Remove - Jewelry, tight clothing from affected limb
5. Position - Affected limb at heart level
6. Document - Mark swelling extent with time
7. Blood draw - Coagulation studies, FBC, U&E, CK, group and screen
8. Tetanus prophylaxis - If not current
9. Contact - Poison control center (US: 1-800-222-1222)

Antivenom Therapy

Indications for Antivenom

Crotalid (Pit Viper) Envenomation:

• Progressive local swelling
• Any systemic symptoms (hypotension, bleeding)
• Coagulopathy (PT/INR elevation, low fibrinogen)
• Thrombocytopenia less than 150 x 10^9/L

Elapid Envenomation:

• Any neurotoxic signs (ptosis, weakness, dysarthria)
• Confirmed coral snake bite (consider empiric treatment before symptoms)
• Coagulopathy (Australian elapids)

General Principles:

• Antivenom is indicated when benefits (preventing death, disability) outweigh risks (allergic reactions)
• Earlier administration is more effective
• Do not delay for severe envenomation
• Amount based on venom neutralization, not patient weight (children receive same dose as adults) [4]

Available Antivenoms

North America:

Australia: [7]

Other Regions:

• India: Polyvalent antivenom (covers "Big Four")
• Africa: Various regional polyvalent antivenoms
• Europe: Viperfav (Vipera spp.)

CroFab Administration Protocol

Preparation:

1. Reconstitute each vial with 18 mL sterile water
2. Mix gently (do not shake)
3. Pool required vials into 250 mL normal saline

Initial Dose:

• 4-6 vials diluted in 250 mL NS
• Infuse over 60 minutes
• Start slowly (25-50 mL/hr for first 10 minutes) to monitor for reactions
• If no reaction, increase rate to complete infusion over 1 hour

Reassessment (1 Hour Post-Infusion):

• If "initial control" achieved (swelling arrested, coagulopathy improving, systemic symptoms stable):
  • Proceed to maintenance dosing
• If not controlled:
  • Repeat 4-6 vials
  • Reassess after each dose until controlled

Maintenance Protocol:

• 2 vials every 6 hours x 3 doses (total 18 hours)
• Reduces recurrent coagulopathy and late local effects

Initial Control Definition:

• Swelling not progressing (no new marking required)
• Vital signs stable
• Laboratory abnormalities stable or improving
• Bleeding stopped
• Neurotoxicity not progressing

Anavip Administration Protocol

Advantages over CroFab:

• Longer half-life of F(ab')2 fragments
• May reduce recurrent coagulopathy
• Single loading dose may suffice without maintenance

Dosing:

• Initial: 10 vials in 250 mL NS over 60 minutes
• Repeat 10 vials if not controlled at 1 hour
• No routine maintenance dosing required

Monitoring for Antivenom Reactions

Acute Allergic Reactions (Anaphylaxis/Anaphylactoid):

• Incidence: 5-20% with earlier whole IgG products; less than 5% with Fab/F(ab')2 products [4]
• Monitor for: urticaria, angioedema, bronchospasm, hypotension
• Have epinephrine, antihistamines, corticosteroids immediately available
• If reaction occurs: stop infusion, treat reaction, then resume at slower rate once stabilized (benefits usually outweigh risks in severe envenomation)

Serum Sickness (Delayed Reaction):

• Onset: 5-14 days after antivenom
• Symptoms: Fever, urticaria, arthralgia, lymphadenopathy
• Incidence: 5-10% with Fab products; higher with whole IgG
• Treatment: Oral corticosteroids (prednisone 1 mg/kg for 5-7 days), antihistamines [15]

Coral Snake Antivenom

Special Considerations:

• Consider prophylactic administration for confirmed bites even without symptoms (delayed onset of potentially irreversible neurotoxicity)
• Equine whole IgG product - higher reaction risk
• Limited supply - contact poison control for availability
• Dose: 3-5 vials initially; may need 10+ vials for severe envenomation

Supportive Care

Wound Management

Analgesia

• Opioids preferred: Morphine, hydromorphone, fentanyl
• Avoid NSAIDs: Worsen coagulopathy and renal injury
• Avoid aspirin: Antiplatelet effects compound bleeding risk
• Regional nerve blocks may be considered for refractory pain

Fluid Management

• IV crystalloid resuscitation for hypovolemia
• Monitor urine output (target > 0.5 mL/kg/hr)
• Aggressive hydration for rhabdomyolysis (target UO 1-2 mL/kg/hr)
• Vasopressors for refractory hypotension after adequate fluid resuscitation

Coagulopathy Management

Antivenom is the primary treatment for VICC. [10]

Blood Product Considerations:

• FFP, cryoprecipitate, platelets generally NOT indicated as first-line
• Reasonable only for:
  • Active life-threatening bleeding
  • Urgent surgery required
  • After adequate antivenom administered
• Without antivenom, replaced factors are rapidly consumed

Tranexamic Acid:

• Limited evidence in snake envenomation
• May be considered for severe hemorrhage after antivenom

Rhabdomyolysis Management

• Aggressive IV fluid resuscitation
• Maintain urine output 1-2 mL/kg/hr
• Monitor potassium (hyperkalemia risk)
• Serial CK measurements
• Renal replacement therapy if oliguric AKI develops

Neurotoxicity Management

Airway Protection:

• Early intubation for:
  • Bulbar dysfunction (aspiration risk)
  • Respiratory muscle weakness
  • Declining vital capacity
• Anticipate prolonged ventilation (days to weeks) for presynaptic toxicity

Anticholinesterase Trial: For postsynaptic neurotoxicity (cobra, some elapids):

• Test dose: Atropine 0.6 mg IV, then neostigmine 1.5-2 mg IV
• Assess for improvement in ptosis, grip strength
• If positive response: Maintenance neostigmine with atropine coverage
• Ineffective for presynaptic toxicity (kraits, taipan)

Fasciotomy Considerations

Clinical Pearl: Fasciotomy is rarely needed with adequate antivenom therapy. Most elevation in compartment pressure is due to subcutaneous venom, not true compartment syndrome. [16]

Indications for Fasciotomy:

• Objective elevated compartment pressures (> 30 mmHg or within 30 mmHg of diastolic)
• Signs of ischemia (pallor, pulselessness, paralysis) despite antivenom
• Failure to respond to additional antivenom

Important Points:

• Always administer additional antivenom before fasciotomy
• Measure compartment pressures objectively
• Consult toxicology and surgery
• Avoid prophylactic fasciotomy - causes significant morbidity

Hyperbaric Oxygen

Not routinely indicated; limited evidence for reducing necrosis. Consider only in specialized centers for severe tissue ischemia unresponsive to antivenom.

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Disposition and Follow-Up

Admission Criteria

ICU Admission:

• Severe envenomation with hemodynamic instability
• Respiratory compromise or intubation
• Significant coagulopathy with bleeding
• Rapidly progressing symptoms

Ward Admission:

• Any antivenom administration
• Moderate envenomation
• Coral snake bite (24-hour observation minimum)
• Significant laboratory abnormalities
• Comorbidities affecting management

Observation for Dry Bite

• Pit viper bites: 8-12 hours with serial examination and labs
• Coral snake bites: 24 hours minimum (delayed onset)
• Australian snake bites: Consider 12-24 hours depending on species likelihood

Discharge Criteria for Dry Bite:

• No local progression after 8-12 hours
• Normal repeat coagulation studies
• No systemic symptoms
• Reliable follow-up possible

Recurrent Coagulopathy

CroFab-specific issue: Fab fragments have short half-life (12-23 hours) compared to venom, leading to recurrence of coagulopathy in 15-20% of cases after initial control. [15]

Management:

• Schedule follow-up coagulation studies at:
  • 2-3 days post-discharge
  • 5-7 days post-discharge
• If recurrent coagulopathy:
  • Usually mild and self-limited
  • Repeat antivenom for clinically significant bleeding or severe lab abnormalities
• Avoid anticoagulants, antiplatelet agents, NSAIDs for 2 weeks
• Avoid elective surgery, dental procedures, contact sports for 2 weeks

Discharge Instructions

Patient Education:

1. Wound care: Keep clean and dry; monitor for infection signs
2. Activity: Elevate extremity; limit activity initially
3. Medications: Avoid NSAIDs, aspirin, anticoagulants for 2 weeks
4. Warning signs to return:
   • Worsening swelling
   • Bleeding from gums, nose, wounds, or in urine/stool
   • Fever
   • Wound drainage or signs of infection
   • Difficulty breathing
   • Numbness or weakness
5. Follow-up: Scheduled laboratory tests and clinic review
6. Serum sickness awareness: Fever, joint pain, rash 1-2 weeks after antivenom

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Special Populations

Pediatric Considerations

• Same antivenom dosing as adults (venom dose, not patient weight)
• Higher venom-to-body-mass ratio may cause more severe envenomation
• Airway compromise may develop more rapidly
• IV access may be challenging; intraosseous if needed
• Weight-based fluid resuscitation
• Lower threshold for ICU admission

Pregnancy

Management Principles: [17]

• Antivenom is pregnancy class C but should NOT be withheld for significant envenomation
• Fetal monitoring from viability
• Left lateral positioning after first trimester
• Monitor for placental abruption, preterm labor
• Obstetric consultation for all significant envenomations
• Coagulopathy poses major risk for delivery complications

Pre-existing Coagulopathy

• Higher risk with baseline coagulation disorders
• Anticoagulant/antiplatelet medications complicate picture
• May need to hold warfarin, DOACs if envenomated
• Consider bridging strategies with hematology input
• Closer monitoring of coagulation parameters

Previous Antivenom Exposure

• Higher risk of allergic reaction with re-exposure
• Skin testing unreliable and delays treatment
• If antivenom needed, premedicate with:
  • Antihistamines (diphenhydramine 50 mg IV)
  • Corticosteroids (methylprednisolone 125 mg IV)
• Slow initial infusion rate
• Have epinephrine ready
• Benefits usually outweigh risks in severe envenomation

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Prevention

Primary Prevention

Secondary Prevention

• Rapid first aid and transport
• Regional antivenom availability
• Emergency department readiness
• Public education programs

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Exam-Focused Content

Common Examination Questions

Viva Point: Opening Statement: "Snake bite envenomation is a toxicological emergency requiring rapid assessment for envenomation syndrome, timely antivenom administration when indicated, and supportive care. Approximately 20-25% are dry bites, and management depends on the snake family involved - Elapidae causing predominantly neurotoxic syndromes and Viperidae causing hemotoxic and cytotoxic effects."

Q1: How do you assess and grade severity of pit viper envenomation?

A: "I would assess severity based on local findings, systemic symptoms, and laboratory abnormalities. Locally, I examine for progressive swelling - minimal envenomation shows swelling at the bite site only, moderate shows swelling beyond one joint, and severe shows extensive swelling with tissue necrosis. Systemically, I assess for nausea, perioral paresthesias, hypotension, or bleeding. Laboratory markers include coagulation studies, with elevation of PT/INR and low fibrinogen indicating significant envenomation. I would document swelling progression by marking the leading edge with time stamps and measuring limb circumference at standardized points."

Q2: What are the indications for antivenom in crotalid envenomation?

A: "Antivenom is indicated for progressive local effects, systemic manifestations, or laboratory abnormalities. Specifically: progression of swelling beyond the immediate bite area, any systemic symptoms including hypotension, nausea beyond early phase, or bleeding, and coagulopathy evidenced by elevated INR, prolonged aPTT, or reduced fibrinogen. I would not give antivenom for isolated dry bites or minimal local swelling that is not progressing, as approximately 20-25% of venomous bites do not result in significant envenomation."

Q3: How does Australian elapid management differ from American pit viper management?

A: "Australian elapid management differs in several key ways. First, pressure immobilization bandaging is recommended for Australian snake bites to slow lymphatic spread, whereas it is contraindicated for cytotoxic pit vipers due to worsening local tissue damage. Second, Australian elapids often cause profound coagulopathy with minimal local signs, requiring a higher index of suspicion. Third, venom detection kits can guide monovalent antivenom selection in Australia. Fourth, the syndrome may include multiple concurrent toxicities - neurotoxicity, coagulopathy, myotoxicity, and nephrotoxicity - requiring comprehensive monitoring and management."

Q4: A patient presents with coral snake bite but no symptoms. How would you manage?

A: "I would admit for a minimum 24-hour observation regardless of symptom status because coral snake neurotoxicity has characteristically delayed onset, often 6-12 hours after bite. I would consider prophylactic antivenom administration given the potentially irreversible nature of presynaptic neurotoxicity and the difficulty obtaining antivenom urgently. I would monitor closely for ptosis, bulbar weakness, and respiratory compromise, maintaining a low threshold for airway protection. Serial neurological examinations and coagulation studies would be performed. If symptoms develop, antivenom is more effective when given early before toxin internalization at the neuromuscular junction."

Q5: How do you manage recurrent coagulopathy after CroFab?

A: "Recurrent coagulopathy after CroFab occurs in 15-20% of cases due to the short half-life of Fab fragments (12-23 hours) compared to persistent venom. I would counsel patients about this risk and schedule follow-up coagulation studies at 2-3 days and 5-7 days post-discharge. I advise avoiding NSAIDs, aspirin, anticoagulants, elective surgery, dental procedures, and contact sports for two weeks. If recurrence is identified, most cases are mild and self-limited. Repeat antivenom is indicated for clinically significant bleeding or severe laboratory abnormalities. Anavip with its F(ab')2 fragments has a longer half-life and may reduce recurrence rates."

Common Mistakes That Fail Candidates

Key Statistics to Remember

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Clinical Pearls

Diagnostic Pearls

1. Mark and time all swelling - Progression is the key indicator of envenomation severity
2. Fibrinogen is most sensitive - May be abnormal before PT/INR in early coagulopathy
3. Absence of fang marks doesn't exclude envenomation - Coral snakes especially may leave subtle marks
4. Repeat labs at 6 hours even if initially normal - Coagulopathy can be delayed
5. Australian snakes may cause severe coagulopathy with minimal local signs - High index of suspicion required

Treatment Pearls

1. Antivenom dosing is independent of patient weight - Based on venom load, not patient size
2. Do not delay antivenom for skin testing - Unreliable and wastes critical time
3. FFP/platelets are NOT substitutes for antivenom - Factors rapidly consumed without venom neutralization
4. Fasciotomy is rarely needed - Almost always try additional antivenom first
5. Anticholinesterases may help postsynaptic but not presynaptic neurotoxicity - Important distinction

Disposition Pearls

1. Coral snake = 24 hours minimum observation - Regardless of initial presentation
2. Pit viper dry bite = 8-12 hours observation - With serial exam and labs
3. All antivenom recipients need follow-up - For recurrent coagulopathy and serum sickness
4. Two-week activity restrictions - No NSAIDs, surgery, contact sports

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Quality Metrics for Snake Bite Management

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References

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2. Kasturiratne A, Wickremasinghe AR, de Silva N, et al. The global burden of snakebite: a literature analysis and modelling based on regional estimates of envenoming and deaths. PLoS Med. 2008;5(11):e218. doi:10.1371/journal.pmed.0050218

3. Warrell DA. Snake bite. Lancet. 2010;375(9708):77-88. doi:10.1016/S0140-6736(09)61754-2

4. Lavonas EJ, Ruha AM, Banner W, et al. Unified treatment algorithm for the management of crotaline snakebite in the United States: results of an evidence-informed consensus workshop. BMC Emerg Med. 2011;11:2. doi:10.1186/1471-227X-11-2

5. Suraweera W, Warrell D, Jotkar R, et al. Trends in snakebite deaths in India from 2000 to 2019 in a nationally representative mortality study. Elife. 2020;9:e54076. doi:10.7554/eLife.54076

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