Management of snake 🐍 bite
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Management of Snake Bite
Snake bite is a medical emergency. Global burden is enormous - up to 2 million envenomations and 100,000+ deaths annually, with highest incidence in rural tropical areas among agricultural workers. Up to one-third of bites by venomous snakes are "dry bites" (no venom injected), but this cannot be assumed in the field.
Clinically Important Snake Families
| Family | Examples | Dominant Venom Effect |
|---|---|---|
| Viperidae (vipers) | Russell's viper, carpet viper, puff adder | Cytotoxic, hemotoxic, local necrosis |
| Crotalinae (pit vipers) | Rattlesnakes, Malayan pit viper | Local tissue destruction, coagulopathy |
| Elapidae | Cobras, kraits, mambas, coral snakes | Neurotoxic (descending paralysis) |
| Hydrophiidae | Sea snakes | Myotoxic, neurotoxic |
Clinical Features
Local envenoming (mainly Viperidae/Crotalinae):
- Immediate burning pain at bite site
- Progressive swelling within minutes to 2 hours, may involve entire limb
- Ecchymosis, petechiae, blistering (serous or serosanguineous)
- Lymphangitis, tender regional lymph nodes
- Tissue necrosis in severe cases
Systemic envenoming:
- Haemotoxic: spontaneous gingival bleeding, epistaxis, haematuria, non-clotting blood (20-minute whole blood clotting test positive)
- Neurotoxic: ptosis (earliest sign - failure of lid retraction on upward gaze), descending paralysis, respiratory muscle weakness, cyanosis
- Cardiovascular: hypotension, shock, arrhythmias
- Renal: oliguria, myoglobinuria ("Coca-Cola" coloured urine from rhabdomyolysis in sea snake/krait bites), acute kidney injury
- Rhabdomyolysis: generalised muscle tenderness and stiffness, elevated creatine kinase
Severity Grading (Crotalid/Pit Viper)
| Grade | Features |
|---|---|
| 0 | Fang marks, no envenomation |
| I | Local swelling/pain only, no systemic signs |
| II | Moderate local + early systemic (nausea, perioral numbness) |
| III | Severe local + systemic (coagulopathy, hypotension) |
| IV | Very severe, life-threatening |
First Aid (Pre-hospital)
DO:
- Reassure the patient - anxiety causes hyperventilation that mimics envenomation
- Immobilize the bitten limb with a splint and broad crepe bandage - prevents muscular contraction which enhances venom absorption and spread via lymphatics
- Transport quickly, comfortably and passively to hospital - patient should not walk
- Bring the snake if it can be killed or secured safely (identification aids treatment)
- For neurotoxic elapid or sea snake bites only: apply pressure immobilization bandage - wrap firmly from bite site up the entire limb; this delays life-threatening neurotoxicity while awaiting intubation capability
DO NOT:
- Incise, excise, cauterize, or apply suction
- Apply ice packs or chemicals
- Give herbal remedies or emetics
- Apply tight tourniquets (except for confirmed neurotoxic elapid bites as above)
- Allow the patient to walk
Hospital Assessment
History: Time of bite, species identification, first aid administered, tetanus status, allergy history (esp. horse/sheep serum - relevant for antivenom)
Examination:
- Fang marks, local swelling (mark leading edge and measure circumference serially)
- Gingival sulci for spontaneous bleeding
- Ptosis (earliest neurotoxic sign)
- Respiratory rate and effort, peak expiratory flow/vital capacity if paralytic envenomation suspected
- Pulse, BP, consciousness, urine output
Investigations:
- 20-minute whole blood clotting test (WBCT20): 2 ml blood in a clean glass tube - failure to clot after 20 min = defibrination (viper envenomation)
- CBC, fibrinogen, prothrombin time, D-dimer
- Urine dipstick (blood/haemoglobin = myoglobinuria)
- Renal function (urea, creatinine)
- ECG
- Peripheral leucocyte count, haematocrit
Observation: All patients bitten by potentially venomous snakes should be observed for at least 24 hours (except confirmed non-venomous species).
Antivenom - The Only Specific Treatment
Antivenom (hyperimmune animal serum, usually equine) neutralizes venom and is the cornerstone of treatment.
Indications (give antivenom when ANY of these are present):
Systemic envenomation:
- Hypotension/shock
- Spontaneous systemic bleeding / non-clotting blood (WBCT20 positive)
- Neurotoxicity (ptosis, respiratory weakness)
- Rhabdomyolysis
- Impaired consciousness
- WBC >20,000/μL, elevated serum enzymes, acidosis
Local envenomation:
- Known necrotic venom species
- Swelling involving >50% of bitten limb
- Rapid progression of swelling
- Bites on digits or tight fascial compartments
Antivenom administration:
- Route: Slow IV infusion (dilute in normal saline) - preferred. Never inject locally at the bite site
- Dose: Minimum 5 vials (10 ml each) as initial dose; children need the same dose as adults (venom dose is the same regardless of body weight)
- Monospecific (species-known) > polyvalent/polyspecific (species unknown or regional coverage)
- Repeat dose after 1 hour if life-threatening signs persist (shock, respiratory paralysis)
- For procoagulant venoms: repeat every 6 hours until WBCT20 normalizes
- Skin/conjunctival sensitivity tests are NOT recommended - no predictive value
Antivenom reactions:
| Type | Timing | Features | Treatment |
|---|---|---|---|
| Early (anaphylactic) | 10 min - 2 h | Urticaria, tachycardia, vomiting, bronchospasm | Adrenaline 0.5-1.0 ml of 1:1000 SC/IM + chlorpheniramine 10 mg IV |
| Pyrogenic | 1-2 h | Fever, rigors | Cooling + antipyretics |
| Late (serum sickness) | 5-24 days | Urticaria, arthralgia, lymphadenopathy | Antihistamine ± prednisolone 5 mg QDS x 5 days |
Even patients with allergy history who have severe envenomation should receive dilute antivenom with concurrent adrenaline - the benefit outweighs risk.
Supportive Treatment
| Problem | Management |
|---|---|
| Respiratory paralysis | Endotracheal intubation + mechanical ventilation (life-saving; antivenom may act too slowly) |
| Hypotension/shock | IV fluids (crystalloid); vasopressors if needed |
| Acute kidney injury | Fluid resuscitation, monitor urine output, dialysis if needed |
| Coagulopathy | Antivenom (primary treatment); FFP/cryoprecipitate if needed |
| Pain | IV opioids |
| Wound infection | Tetanus prophylaxis; antibiotics only if secondary infection develops |
| Rhabdomyolysis | IV fluids, urine alkalinization, monitor renal function |
Surgical Aspects
- Fasciotomy is indicated only if compartment syndrome is confirmed by compartment pressure measurement AND antivenom has failed at adequate doses - not prophylactically
- Debridement of necrotic tissue once the patient is stabilized
- Skin grafting for large necrotic areas
- Surgical intervention has a limited role in most cases - antivenom and supportive care come first
Indian Subcontinent - "Big Four"
The four species responsible for most deaths in India:
- Russell's viper (Daboia russelii) - hemotoxic + nephrotoxic
- Indian cobra (Naja naja) - cytotoxic + neurotoxic
- Indian krait (Bungarus caeruleus) - potent neurotoxin, painless bite, nocturnal
- Saw-scaled viper (Echis carinatus) - hemotoxic, coagulopathy
Polyvalent anti-snake venom (ASV) covering all four species is manufactured in India and is the standard treatment.
Prevention
- Wear boots and long trousers in endemic areas
- Use a torch/flashlight at night
- Avoid disturbing snakes
- Sleep off the ground (krait bites occur to sleeping persons)
- Community education on first aid and what NOT to do
Sources:
- Pye's Surgical Handicraft (22nd ed.) - Chapter 28: Snake Bite
- Rosen's Emergency Medicine - Chapter 53: Emergency Department Care of Snakebite
- Tintinalli's Emergency Medicine - Snakebite
Recent evidence: A 2025 systematic review (PMID 41328212) and 2025 meta-analysis on Asian snakebite outcomes (PMID 40691949) confirm antivenom remains the standard of care; a 2026 systematic review on snakebite-associated AKI (PMID 41776424) underscores acute kidney injury as a major cause of snakebite mortality, particularly from viperid envenomation.
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