Management of Snakebite - Comprehensive Clinical Guide

1. Epidemiology and Background

• Harrison's Principles of Internal Medicine, 22nd Ed.

2. Classification of Venomous Snakes

3. Pathophysiology of Venom

Crotaline (Pit Viper) Venom

• Local tissue injury via proteolytic enzymes, collagenase, elastase
• Vascular damage - increased permeability, plasma extravasation, hypovolemia
• Hematologic effects - fibrinogenolysis, platelet consumption, coagulopathy/DIC
• Hemolysis via phospholipase A2
• Neurotoxicity (in some species) - blocks neuromuscular transmission causing ptosis, respiratory failure

Elapid Venom

• Tremor, salivation, dysarthria, diplopia
• Bulbar paralysis, ptosis, fixed pupils
• Dysphagia, dyspnea, respiratory muscle failure
• Cobras additionally cause severe local pain and necrosis

Key Venom Enzymes

• Sabiston Textbook of Surgery, 7th Ed.

4. Grading of Envenomation Severity

• Harrison's Principles of Internal Medicine, 22nd Ed.

5. Field Management (Pre-hospital)

What TO Do

1. Rapid transport to a medical facility capable of providing antivenom - this is the single most important step
2. Remove all jewelry, watches, tight clothing near the bite site (anticipated swelling)
3. Wound care - clean with soap and running water, cover with sterile dressing (but do not delay transport for this)
4. Splint the limb to limit movement; maintain at approximately heart level in a neutral position
5. Keep the victim calm and still - physical activity disperses venom via muscle pumping
6. Photograph the snake from a safe distance to assist identification - do not attempt to catch or handle the snake (reflexive bites from dead snakes can still occur)
7. Pressure-immobilization technique - recommended specifically for elapid (neurotoxic) bites: wrap the entire bitten limb firmly (snug but not occlusive - one finger should slip under) at 40-70 mmHg for upper limb and 55-70 mmHg for lower limb; immobilize with a splint; carry the patient out
8. Do not wash the wound initially - traces of venom on skin can help identify the species and guide antivenom choice

What NOT to Do

• No incision and suction - exacerbates local tissue damage, increases infection risk, shown to be ineffective
• No tourniquet for viper bites - viper venom contains procoagulant enzymes; tourniquet concentrates them in a confined space, and release causes sudden venom bolus and risk of embolism
• No ice/cryotherapy - worsens ischemia
• No electric shock - ineffective and harmful
• No traditional/herbal remedies - cause dangerous delays in reaching definitive care
• Harrison's Principles of Internal Medicine, 22nd Ed.; P.C. Dikshit Textbook of Forensic Medicine and Toxicology

6. Hospital Assessment

History

• Time and location of bite
• Description of snake (color, size, pattern, head shape)
• Symptoms since bite - pain, swelling, paresthesia, weakness, nausea, visual changes
• First-aid measures already applied
• Patient's medical history, medications, allergies (especially equine proteins for older antivenom)

Physical Examination

• Vital signs - BP, HR, RR, temperature, O2 saturation continuously monitored
• Bite wound - fang marks (number, pattern, depth), local swelling, ecchymosis, blistering, necrosis
• Limb circumference - measure every 15 minutes proximal to the bite site until swelling stabilizes, then every 1 hour
• Neurological - ptosis, diplopia, dysarthria, muscle weakness, altered consciousness
• Cardiovascular - hypotension, arrhythmia
• Respiratory - signs of respiratory muscle compromise

Initial Investigations

• Harrison's Principles of Internal Medicine, 22nd Ed.; Tintinalli's Emergency Medicine, Comprehensive Study Guide

7. Antivenom Therapy

Indications for Antivenom

• Progressive local swelling crossing joints or involving more than half the bitten limb
• Any systemic envenomation (coagulopathy, neurotoxicity, cardiovascular instability, shock, respiratory distress)
• Moderate or severe envenomation grade
• Confirmed coral snake envenomation (prophylactic, before symptoms develop, because effects are irreversible once established)

Antivenom Types

• CroFab (Crotalidae Polyvalent Immune Fab, Ovine) - purified Fab fragments; starting dose 4-6 vials for moderate, 6 vials for severe
• ANAVIP (Crotalidae Immune F(ab')2, Equine) - starting dose 10 vials; longer half-life (~133 hours vs ~15 hours for CroFab), stored at room temperature, less costly per vial

• Coral snake: Anti-venin (M. fulvius), 3-5 vials IV at first confirmed bite
• Cobras, kraits, others: Species-specific polyvalent antivenoms per regional formulary

Administration Protocol

1. Reconstitute vials and dilute in 250 mL normal saline
2. Begin IV infusion at 25-50 mL/h for the first 10 minutes with physician present
3. If no reaction, increase to 250 mL/h and complete over 1 hour
4. Never give IM or directly into a digit (venom-induced hypovolemia retards absorption; digit injection risks ischemia)
5. For FabAV: once initial control is established (cessation of progression of all local effects, systemic effects, coagulopathy), give 2-vial maintenance doses at 6, 12, and 18 hours
6. Initial control = cessation of all progression; document initial control carefully - the most common management error is insufficient early dosing

Antivenom Adverse Reactions

• Children: same number of vials as adults (children receive proportionally more venom per body mass); may reduce total volume
• Pregnancy: treat when indicated; coagulopathy can be lethal to mother and fetus; reported fetal loss up to 20% in untreated bites, improved with antivenom
• Sabiston Textbook of Surgery; Tintinalli's Emergency Medicine; Harrison's 22nd Ed.

8. Supportive Management

Resuscitation

• Establish two large-bore IV lines
• If hypotensive: isotonic crystalloid bolus 20-40 mL/kg IV
• Vasopressors for refractory shock if not responsive to fluids and antivenom
• Supplemental oxygen; be prepared for intubation (particularly in elapid bites causing respiratory failure)

Wound Care

• Clean and dress the wound
• Tetanus prophylaxis as indicated
• Antibiotics only if signs of secondary infection (prophylactic antibiotics are not routinely recommended - snake mouths are not the source of serious infection in typical bites)

Coagulopathy / DIC

• Antivenom is the primary treatment - correct coagulopathy first with antivenom before FFP or platelets
• If severe bleeding despite antivenom: FFP, platelets, cryoprecipitate as needed
• Avoid IM injections until coagulopathy is corrected

Neurotoxic Envenomation (Elapids)

• Monitor serial pulmonary function - inspiratory pressure and vital capacity
• Intensive care monitoring for respiratory depression
• Intubation and mechanical ventilation may be required and prolonged
• Neostigmine + atropine may reverse postsynaptic (not presynaptic) neurotoxicity in some elapid envenomations (e.g., cobras); consult poison control

Acute Kidney Injury

• Monitor urine output closely (especially with Russell's viper envenomation)
• Aggressive IV fluid to maintain urine output >0.5 mL/kg/h
• Hemodialysis for oliguria/anuria not responding to fluids
• Systematic review (PMID: 41776424) confirms AKI as a major complication of snake envenomation requiring early recognition

Rhabdomyolysis

• Aggressive IV hydration
• Forced alkaline diuresis (sodium bicarbonate) to prevent renal tubular damage
• Monitor CK, myoglobin, potassium

9. Compartment Syndrome

The most effective treatment for compartment syndrome from snakebite is neutralization of venom with antivenom, not immediate surgery. Fasciotomy is a last resort.

• Tintinalli's Emergency Medicine

• Harrison's Principles of Internal Medicine, 22nd Ed.

10. Special Considerations by Snake Type

Viper Bites (Crotalinae and Viperinae)

• Dominant local effects (swelling, hemorrhage, necrosis) + systemic hemotoxicity
• Pressure-immobilization not recommended (may worsen local tissue damage from necrotizing venom)
• Antivenom is the mainstay; dose driven by severity
• Watch for DIC, AKI, compartment syndrome, hypovolemic shock

Elapid Bites (Cobra, Krait, Coral Snake)

• Minimal local effects, predominantly neurotoxic
• Pressure-immobilization technique is appropriate here
• Admit all confirmed bites for observation - symptoms may be delayed hours
• Give antivenom preemptively for confirmed coral snake bite; neurological effects, once established, cannot be reversed
• Prolonged ICU ventilatory support may be needed
• Spitting cobras: ocular venom exposure - irrigate eyes immediately with copious water/saline; ophthalmic review

Sea Snakes (Hydrophiinae - Elapidae)

• Up to 75% dry bites
• True envenomation causes generalized myalgia, trismus, bulbar paralysis, myoglobinuria
• Treat with sea snake antivenom (polyvalent)

11. Criteria for Discharge and Follow-up

• Swelling begins to resolve
• Coagulopathy has been reversed and remains stable
• Patient is ambulatory

• Physical therapy for the bitten extremity (especially hand) once swelling and coagulopathy resolve
• Return to ED if symptoms recur, bruising reappears, or signs of recurrent coagulopathy develop
• Educate on symptoms of serum sickness (urticaria, joint pains, fever 7-21 days post-bite) and advise to return

12. What Not to Do - Summary

13. Summary Algorithm

SNAKEBITE
    |
    v
PREHOSPITAL: Remove jewelry → Clean wound → Splint limb at heart level
Elapid bite? → Pressure-immobilization bandage → Carry (do NOT walk)
Viper bite? → Do NOT use pressure bandage → Rapid transport
    |
    v
EMERGENCY: ABC assessment → 2 large-bore IVs → O2 → Monitoring
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    v
IDENTIFY: Species if possible, grade severity (none/mild/moderate/severe)
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    v
LABS: CBC, coag, fibrinogen, metabolic, CK, U/A, type & cross
    |
    v
ANTIVENOM (if moderate/severe/any systemic sign):
  Pit viper → CroFab 4-6 vials / ANAVIP 10 vials IV over 1h
  Coral snake → Anti-venin (M. fulvius) 3-5 vials IV
  Cobra/krait → Regional polyvalent antivenom
    |
    v
MONITOR: Repeat limb measurements, labs q4-6h
    |
    v
TREAT COMPLICATIONS:
  Shock → Crystalloid bolus ± vasopressors
  Coagulopathy → Antivenom first; FFP/platelets if severe bleeding
  AKI → IV fluids, dialysis if needed
  Compartment → Mannitol + antivenom; fasciotomy last resort
  Respiratory failure → Intubation ± ventilator
  Neurotoxicity → ICU monitoring; neostigmine for postsynaptic elapid
    |
    v
DISCHARGE: Stable labs → Ambulatory → Serum sickness education → F/U

Sources

• Harrison's Principles of Internal Medicine, 22nd Edition (2025) - Chapter 471
• Tintinalli's Emergency Medicine: A Comprehensive Study Guide - Chapter 212
• Sabiston Textbook of Surgery, Biological Basis of Modern Surgical Practice - Chapter 44
• Mulholland and Greenfield's Surgery, Scientific Principles and Practice, 7th Ed.
• P.C. Dikshit Textbook of Forensic Medicine and Toxicology