Snake Bite in India: Diagnosis, Management & Treatment

Epidemiology

• India has ~216 snake species, of which 52 are venomous
• Only 50% of bites by venomous species result in actual envenomation
• 70% of all snakebites are from non-venomous snakes

The "Big Four" Medically Important Snakes in India

1. Common Cobra (Naja naja) - Elapidae

• Spectacle mark on dorsal hood (binocellate/monocellate)
• Large head scales; round pupil; grooved, short fangs
• Three varieties: N. naja (most of India), N. kaouthia (Bengal, Odisha, UP), N. oxiana (J&K, Punjab, Rajasthan)
• Venom: Neurotoxic (postsynaptic alpha-neurotoxin)

2. Common Krait (Bungarus caeruleus) - Elapidae

• Steel-blue, 1.0-1.5 m; single or double white bands across back
• Key ID: hexagonal scales in central row; entire (undivided) subcaudal plates
• Nocturnal; found throughout India; bites sleeping victims
• The most common venomous snake in India
• Venom: Neurotoxic (presynaptic beta-neurotoxin - blocks ACh release; harder to reverse with neostigmine)

3. Banded Krait (Bungarus fasciatus)

• Jet black 5cm-wide bands alternating with deep yellow bands; 1.5-2 m
• Found in Bengal, Odisha, MP, Andhra, Assam

4. Russell's Viper (Daboia russelii) - Viperidae

• Flat, heavy triangular head; V-shaped mark pointing forwards
• Three rows of diamond-shaped black/brown spots; whitish body with dark semilunar spots
• Short, tapering tail; hisses loudly; found throughout India
• Venom: Hemotoxic/cytotoxic + some neurotoxicity (especially in South India/Sri Lanka)

5. Saw-Scaled Viper (Echis carinatus)

• Brown, ~0.5 m; triangular head; wavy white lines on flanks with diamond-shaped areas between
• White mark on top of head resembling a bird's footprint
• Found throughout India
• Venom: Hemotoxic (potent pro-coagulant)

Cobra vs. Viper - Key Differences

Venom Composition & Mechanisms

• Postsynaptic neurotoxins (cobra): block nicotinic ACh receptors - partially reversible with neostigmine
• Presynaptic neurotoxins (krait beta-bungarotoxin): prevent ACh release at nerve terminals - largely irreversible with neostigmine

• Rich in proteases, phospholipases, and procoagulant enzymes
• Cause venom-induced consumption coagulopathy (VICC)
• Russell's viper also contains phospholipase A2 causing rhabdomyolysis and AKI

Clinical Features

Local Envenoming

• Fang marks (may be single or paired); persistent bleeding from fang marks = coagulopathy
• Local swelling starting within minutes (Viperidae) - can involve entire limb + adjacent trunk within days
• Linear erythema/bruising along lymphatics; tender lymphadenopathy
• Blisters (serous or haemosanguinous), bullae, ecchymosis
• Necrosis in 10-15% of viper bites - skin, subcutaneous tissue, muscle

Systemic Envenoming

• Ptosis (earliest sign) → ophthalmoplegia → dysarthria → dysphagia
• Descending paralysis - inability to raise head ("broken neck sign")
• Respiratory failure (cause of death)
• Patient conscious but unable to speak; coma then respiratory arrest
• Cobra: drowsiness/heavy eyelids, + possible cardiac toxicity
• Krait: intense drowsiness/intoxication; albuminuria

• Severe pain at bite site within 8 minutes; redness
• Persistent bleeding from bite + other sites (gums, epistaxis, hemoptysis, hematuria)
• Prolonged bleeding/clotting time; DIC
• Epistaxis, hemoptysis, ecchymoses, intracranial haemorrhage, GI/GU bleeding
• Renal failure (myoglobinuria, hemolysis, direct tubular toxicity) - "mahogany-coloured" urine
• Hypotension, shock in severe cases
• In some regions, Russell's viper also causes neurotoxicity + pituitary haemorrhage (Sheehan-like syndrome)

1. Snake identified as very dangerous species
2. Rapid early extension of local swelling from bite site
3. Early tender enlargement of regional lymph nodes
4. Collapse (hypotension, shock), severe nausea/vomiting, diarrhoea
5. Heavy eyelids/inappropriate drowsiness; early ptosis/ophthalmoplegia
6. Early spontaneous systemic bleeding from any site
7. Dark brown/black urine (myoglobinuria/haemoglobinuria)

Diagnosis

Clinical Assessment

• History: time, circumstances, snake description, symptom progression
• Examine fang marks, local swelling extent, lymphadenopathy
• Neurological exam: ptosis, eye movements, reflexes, respiratory effort
• Watch for bleeding from gums, injection sites, venepuncture sites

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

• Take a few mL of fresh venous blood in a clean dry glass tube
• Leave undisturbed for 20 minutes, then gently tilt
• If blood is still liquid = incoagulable = viper bite with VICC
• Repeat every 6 hours to determine repeat dose requirement
• Normalization of clotting = endpoint of therapy
• After normalization, repeat at 12-hour intervals for 48 hours to detect recurrence

Laboratory Investigations

Management

First Aid (Community/Pre-Hospital)

1. Reassure the patient - fear/anxiety worsen symptoms
2. Immobilize the bitten limb with a splint/sling - prevent muscular movement that enhances venom absorption
3. Transport quickly, comfortably and passively to hospital
4. Remove rings, bracelets, watches, tight footwear from bitten limb
5. If snake identified as neurotoxic elapid - apply pressure immobilization bandage (firm crêpe bandage from bite site upward, do not occlude circulation)
6. Recovery position (left lateral) to protect airway

• Apply tight tourniquets or constricting bands (dangerous, do not work)
• Incise, cut, suck, cauterize or excise the bite site
• Apply ice packs, electric shocks, or herbal remedies
• Give alcohol or stimulants (vasodilators - speed venom absorption)
• Elevate the bitten extremity (hastens systemic absorption)

Hospital Assessment: Critical vs. Non-Critical Arrival

• Descending paralysis, ptosis, respiratory distress
• Spontaneous bleeding
• Hypotension/shock
• Dark urine
• Incoagulable blood (20WBCT positive)

Anti-Snake Venom (ASV) - The Definitive Treatment

Indian Polyvalent ASV (PAV)

• 0.60 mg dried Indian Cobra (Naja naja) venom
• 0.45 mg dried Common Krait (Bungarus caeruleus) venom
• 0.60 mg dried Russell's Viper (Daboia russelii) venom
• 0.45 mg dried Saw-Scaled Viper (Echis carinatus) venom

Indications for ASV

• Rapidly developing swelling involving at least half the bitten limb within a few hours
• Swelling crossing a joint within 1-2 hours of onset
• Incoagulable blood (20WBCT positive) or spontaneous systemic bleeding
• Signs of neurotoxicity (ptosis, ophthalmoplegia, respiratory distress)
• Cardiovascular abnormalities (hypotension, arrhythmia)
• Dark brown/black urine (myoglobinuria)
• Rapidly developing severe local necrosis

ASV Dosing (Indian Standard Guidelines)

• Lyophilized powder dissolved in 500 mL normal saline/distilled water
• IV infusion over 1 hour
• For neurotoxic poisoning: second dose of 10 vials after 1 hour if no improvement
• For hemotoxic: repeat dose after 6 hours if 20WBCT remains incoagulable (liver needs 6 hours to restore clotting factors)
• Most effective if given within 4 hours; less effective at 8 hours; doubtful after 24 hours (though still indicated if systemic envenomation persists)

Managing ASV Reactions

1. Stop ASV infusion immediately
2. Adrenaline 0.5 mg IM (1:1000) for adults; 0.01 mg/kg for children
3. Hydrocortisone IV + antihistamine for longer protection
4. If no improvement in 10-15 minutes: second dose of adrenaline
5. Restart ASV infusion once condition improves

Specific Management by Snake Type

Neurotoxic (Cobra/Krait Bite)

• ASV as above
• Airway management is paramount - monitor respiratory rate and SpO2 continuously
• If SpO2 <90%: mechanical ventilation required
• Neostigmine test (for postsynaptic neurotoxicity - primarily cobra):
  • Adults: neostigmine 1.5 mg IM + atropine 0.6 mg IV
  • Children: neostigmine 0.04 mg/kg + atropine 0.05 mg/kg
  • Repeat twice at 10-minute intervals; if improvement shown, continue neostigmine 0.5 mg IM half-hourly + atropine
  • Primarily useful for cobra bites (postsynaptic block); less effective for krait (presynaptic)
• "Broken neck sign" (inability to raise head) may persist 3-5 days despite ASV - does not indicate treatment failure

Hemotoxic (Russell's Viper/Saw-Scaled Viper Bite)

• Monitor 20WBCT every 6 hours
• ASV: repeat if 20WBCT still positive at 6 hours
• Fresh whole blood or FFP if severe bleeding (blood bank ASV cannot undo damage already done)
• Monitor renal function closely - snakebite accounts for >70% of AKI in some South Asian regions
• Manage hypotension: IV fluids, plasma expanders; dopamine 2.5-5 mcg/kg/min for refractory shock
• Dialysis (peritoneal or haemodialysis) if oliguria fails to respond to conservative management
• Heparin is NOT effective and may worsen bleeding - never use in snakebite
• Antifibrinolytic agents are NOT effective

Renal Failure (Common with Russell's Viper)

• Maintain hydration; cautious rehydration + diuretics + low-dose dopamine for oliguria
• Peritoneal dialysis or haemodialysis when uraemia develops
• Monitor for hyperkalaemia (from rhabdomyolysis)

Surgical Management

• Early surgery is generally NOT recommended in the acute phase, especially in coagulopathic/hypotensive patients
• Fasciotomy is controversial and rarely needed; measure compartment pressures before performing (most "compartment syndrome" signs are from the envenoming itself, not true elevated pressures)
• Blisters and bullae: leave intact; aspirate only if large and at risk of rupture (fine needle aspiration)
• Wound care: prophylactic antibiotics (penicillin or erythromycin; add gentamicin or cefuroxime if wound was tampered with); tetanus toxoid booster
• Debridement: indicated at earliest signs of established necrosis; requires adequate anaesthesia (tissue damage often far more extensive than surface appearance suggests)
• Split-skin grafting recommended immediately after debridement
• Amputation: last resort; every effort should be made to preserve limb

Complications

Referral Criteria

• Requiring mechanical ventilation
• AKI needing dialysis
• Refractory shock
• Severe coagulopathy/haemorrhage
• Extensive necrosis requiring advanced surgical management

Prevention

• Wear boots and protective clothing in agricultural fields
• Use a torch when walking at night
• Sleep on raised beds (not on floor, especially in krait territory)
• Do not reach into dark holes or under logs
• Snake-bite should be made a notifiable disease in India
• Snakebite programme: standard treatment guidelines, training, adequate ASV supply at all health levels

• KS Narayan Reddy's Essentials of Forensic Medicine & Toxicology, 36th Ed. (2026)
• Pye's Surgical Handicraft, 22nd Ed.
• Park's Textbook of Preventive & Social Medicine
• Goldman-Cecil Medicine, International Ed.
• NHM India Standard Treatment Guidelines - Snakebite
• India National Action Plan for Snakebite Envenoming (NAPSE)
• Bhaumik S et al. Core outcome set for snakebite envenomation in South Asia. Inj Prev 2026 [PMID: 39266207]