Snakebite envenomation

Red Flags

Systemic envenomation (neurotoxic paralysis, ptosis, dysphagia, respiratory distress; haemotoxic bleeding; rhabdomyolysis; AKI) — emergency ASV; intubation if respiratory failure; ICU^[1]
Anaphylactic reaction to ASV (urticaria, hypotension, bronchospasm) — adrenaline 0.5 mg IM; pause and recommence ASV at slower rate after stabilisation^[1]
Krait bite (often nocturnal, painless local site, progressive paralysis 6–12 h post-bite) — high suspicion even without local signs; do NOT use atropine-neostigmine challenge in confirmed krait^[1]
Compartment syndrome from severe local swelling (cobra, Russell's viper) — measure compartment pressures; surgical decompression if intra-compartment pressure >40 mmHg or clinical features^[1]

First-line treatment

Interventions

First aid — reassurance, immobilisation, transport^[1]
Reassure; immobilise limb with splint; remove tight clothing/jewellery; transport to ASV-equipped facility immediately. Avoid tourniquets, incisions, suction, ice, traditional remedies — all cause harm and delay
Hospital initial assessment^[1]
ABCDE; secure airway if respiratory compromise; IV access ×2; bloods; 20WBCT; mark progression of swelling with skin marker; serial neurological assessment; observe minimum 24 h before discharge if asymptomatic
Polyvalent ASV indications^[1]
Systemic envenomation (incoagulable 20WBCT, neurotoxicity, rhabdomyolysis, AKI, haemodynamic instability) OR severe progressive local envenomation. Initial dose 10 vials in 100 mL normal saline IV over 30–60 min; repeat 10 vials every 6 h until 20WBCT normalises and neurology improves
Pre-medication and reaction management^[1]
Adrenaline 0.25 mg SC or 1:1000 IM 5 min before ASV (national programme practice; some protocols selective); IV antihistamine and hydrocortisone; have full anaphylaxis kit ready; if reaction occurs, pause ASV, treat anaphylaxis, restart at slower rate
Atropine-neostigmine for cobra envenomation^[1]
Indicated for cobra envenomation (post-synaptic neurotoxicity); atropine 0.6 mg IV + neostigmine 1.5 mg IV; reassess at 30 min; repeat if response. AVOID in krait envenomation (presynaptic neurotoxicity does not respond)
Supportive care for haemotoxic envenomation^[1]
Fluid resuscitation; blood products only after ASV given (giving FFP/platelets without ASV is futile and risks transfusion reaction); haemodialysis for AKI; avoid NSAIDs and other nephrotoxins
Tetanus prophylaxis and wound care^[1]
Tetanus toxoid booster if last dose >5 years; tetanus immunoglobulin if not fully immunised; clean wound; do not debride routinely; antibiotic only if cellulitis or bite contamination evident

First-line drug therapy

Drug	Class	Adult	Paediatric	Notes
Indian Polyvalent Anti-Snake Venom (ASV)^[1]	Equine F(ab')2 / IgG anti-venom	10 vials reconstituted in 100 mL 0.9% saline IV over 30–60 min; repeat 10 vials every 6 h until 20WBCT coagulable and neurology improving (max ~30 vials)	Same dose as adults — venom dose is fixed, not weight-based	Covers four species (Russell's viper, cobra, krait, saw-scaled viper) in Indian polyvalent preparation; check expiry; reconstitute correctly; pre-medication and reaction monitoring
Adrenaline (anaphylaxis prophylaxis / treatment)^[1]	Sympathomimetic	Pre-ASV: 0.25 mg SC or 1:1000 IM 5 min before ASV. Treatment of anaphylaxis: 0.5 mg IM repeated every 5 min as needed	10 µg/kg IM (max 0.5 mg)	Subcutaneous pre-medication per Indian programme; full anaphylaxis kit and IV access at all times during ASV administration
Atropine + neostigmine (cobra envenomation)^[1]	Anticholinergic + acetylcholinesterase inhibitor	Atropine 0.6 mg IV + neostigmine 1.5 mg IV; assess at 30 min; repeat as response	Atropine 50 µg/kg + neostigmine 0.04 mg/kg IV	Cobra envenomation neuroparalysis (post-synaptic); not effective in krait; combines with ASV; adequate atropinisation prevents bradycardia from neostigmine
Hydrocortisone + chlorphenamine (reaction)^[1]	Glucocorticoid + antihistamine	Hydrocortisone 100 mg IV; chlorphenamine 10 mg IV	Hydrocortisone 4 mg/kg IV; chlorphenamine 0.2 mg/kg IV	Adjunct to adrenaline in delayed reactions; not substitute for adrenaline in anaphylaxis; serum sickness 7–10 days after ASV warrants oral steroid

Indian Polyvalent Anti-Snake Venom (ASV)^[1]

Equine F(ab')2 / IgG anti-venom

Adult: 10 vials reconstituted in 100 mL 0.9% saline IV over 30–60 min; repeat 10 vials every 6 h until 20WBCT coagulable and neurology improving (max ~30 vials)
Paediatric: Same dose as adults — venom dose is fixed, not weight-based

Covers four species (Russell's viper, cobra, krait, saw-scaled viper) in Indian polyvalent preparation; check expiry; reconstitute correctly; pre-medication and reaction monitoring

Adrenaline (anaphylaxis prophylaxis / treatment)^[1]

Sympathomimetic

Adult: Pre-ASV: 0.25 mg SC or 1:1000 IM 5 min before ASV. Treatment of anaphylaxis: 0.5 mg IM repeated every 5 min as needed
Paediatric: 10 µg/kg IM (max 0.5 mg)

Subcutaneous pre-medication per Indian programme; full anaphylaxis kit and IV access at all times during ASV administration

Atropine + neostigmine (cobra envenomation)^[1]

Anticholinergic + acetylcholinesterase inhibitor

Adult: Atropine 0.6 mg IV + neostigmine 1.5 mg IV; assess at 30 min; repeat as response
Paediatric: Atropine 50 µg/kg + neostigmine 0.04 mg/kg IV

Cobra envenomation neuroparalysis (post-synaptic); not effective in krait; combines with ASV; adequate atropinisation prevents bradycardia from neostigmine

Hydrocortisone + chlorphenamine (reaction)^[1]

Glucocorticoid + antihistamine

Adult: Hydrocortisone 100 mg IV; chlorphenamine 10 mg IV
Paediatric: Hydrocortisone 4 mg/kg IV; chlorphenamine 0.2 mg/kg IV

Adjunct to adrenaline in delayed reactions; not substitute for adrenaline in anaphylaxis; serum sickness 7–10 days after ASV warrants oral steroid

Safety-net

Avoid tourniquets, incisions, suction, ice, and traditional remedies — they cause harm and delay reaching definitive treatment^[1]
Most bites are without envenomation ('dry bites') — observation for 24 h is essential as venom effects can be delayed (especially krait bites)^[1]
After discharge, watch for delayed bleeding, weakness recurring, dark urine, or decreased urine — return immediately for re-evaluation^[1]

Referral criteria

Suspected systemic envenomationEmergency department with ASV; ICU on respiratory or haemodynamic compromise^[1]
Refractory neurological deficit despite ASV and atropine-neostigmineTertiary toxicology / critical care for prolonged ventilation; consider repeat ASV^[1]
AKI requiring dialysisNephrology and ICU^[1]
Compartment syndrome of bitten limbOrthopaedics / vascular for fasciotomy after compartment pressure measurement^[1]

Clinical summary

First aid, recognition of systemic envenomation, anti-snake venom administration, and supportive care for snakebite in adults and children.

References

1.MoHFW Standard Treatment Guideline — Management of Snakebite (2021); WHO Guidelines for the Management of Snakebites in South-East Asia (2016, updated 2024) (2024)