Snakebite and ASV Management Protocol

Evidence-Based Pearls

1. India's Snakebite Burden

The scale of it: The Million Death Study, which is the largest nationally representative estimate, puts it at about 45,900 snakebite deaths a year in India (99% CI 40,900 to 50,900). The figure of 58,000 still widely quoted is an earlier estimate. Either way India carries close to half the world's snakebite mortality. Of 310+ snake species here, 66 are venomous, and 4 of them account for 90% of envenoming: the Big Four.

WHO NTD Status: Snakebite envenoming was recognised as a Neglected Tropical Disease (NTD) by WHO in 2017.
Seasonality: Peak incidence during monsoon (June to September).
Krait Nocturnal Bites: ~65.7% of snakebite deaths are from Common Krait, which bites sleeping victims at night. The bite is often painless and may go unnoticed.

2. Venomous vs Non-Venomous Snakes: Key Differentiators

Teaching point: None of these features is reliable enough to decide treatment on, and the snake is rarely brought in anyway. Treat the syndrome in front of you, not the identification.

Feature	Typically Venomous	Typically Non-Venomous
Head shape	Triangular (Vipers); may be rounded (Elapids)	Usually rounded or oval
Pupil	Vertical slit (Vipers); round (Elapids)	Round
Fangs	Two prominent fangs	Rows of small, uniform teeth
Bite marks	1-2 puncture marks, spaced apart	Multiple small tooth marks (horseshoe pattern)

3. The "Big Four" Venomous Snakes of India

Key Fact: Indian polyvalent ASV is manufactured using venoms of these 4 species. It does NOT cover Hump-nosed Pit Viper (Hypnale hypnale), Banded Krait, or King Cobra.

Indian Spectacled Cobra (Naja naja)

Indian Spectacled Cobra with hood raised, showing the spectacle mark — Hood raised: spectacle mark on the back of the hood

Close-up of Indian Spectacled Cobra head showing round pupil — Head close-up: round pupil, no heat-sensing pit

Venom Type	Neurotoxic (post-synaptic) + cytotoxic
Clinical Signature	Rapid onset ptosis, descending paralysis, respiratory failure. Painful bite with severe local necrosis.

Common Krait (Bungarus caeruleus)

Common Krait showing steel blue-black body with narrow white crossbands — Body pattern: white crossbands on steel blue-black

Close-up of Common Krait head, small and barely distinct from the neck — Head close-up: small, barely wider than the neck

Venom Type	Neurotoxic (pre-synaptic; responds poorly to neostigmine)
Clinical Signature	Painless bite. Delayed onset paralysis, colicky abdominal pain. Mortality is high, because the respiratory failure comes on during sleep and is found late.

Russell's Viper (Daboia russelii)

Russell's Viper showing three rows of chain-like oval spots on a lighter background — Body pattern: three chains of oval, dark-bordered spots

Close-up of Russell's Viper head, triangular and distinct from the neck — Head close-up: broad and triangular, no heat-sensing pit

Venom Type	Haemotoxic + nephrotoxic (South Indian variants add neurotoxicity)
Clinical Signature	Extremely painful bite. Non-clotting 20WBCT, systemic bleeding, DIC, AKI, and profound local swelling.

Saw-Scaled Viper (Echis carinatus)

Saw-Scaled Viper showing a pale zigzag body pattern, much smaller than the other three — Body pattern: pale zigzag band, rarely over 60 cm

Close-up of Saw-Scaled Viper lateral scales, serrated and keeled — Serrated side scales: rubbed together to make the warning sound

Venom Type	Haemotoxic (potent pro-coagulant)
Clinical Signature	Severe coagulopathy, spontaneous bleeding. The snake makes a distinctive "sizzling" warning sound.

4. 20-Minute Whole Blood Clotting Test (20WBCT)

The bedside test that decides ASV: A pooled meta-analysis puts the 20WBCT at 91% specific and 84% sensitive for coagulopathy (defined as INR above 1.4), and it needs nothing from the laboratory. A clean dry glass tube and 20 minutes.

What the sensitivity means at the bedside: One clotted result on arrival does not rule out coagulopathy that has not yet declared itself.

Step 1: Collect 2 ml of freshly sampled venous blood.
Step 2: Place in a NEW, CLEAN, DRY glass tube. Do NOT use plastic tubes or injection vials.
Step 3: Leave UNDISTURBED for exactly 20 minutes.
Step 4: After 20 minutes, gently tilt the tube once. Do NOT shake.
Result: Blood runs out = POSITIVE. Firm clot = NEGATIVE.

5. ASV Dosing: Indian National Protocol

Paediatric Principle: ASV dose neutralises venom load, NOT body weight. A child receives the SAME dose as an adult.

Syndrome	Initial (Loading) Dose	Maximum
Haemotoxic	10 vials in 200 ml NS IV over 1 hour	25-30 vials
Neurotoxic	10 vials in 200 ml NS IV over 1 hour	20 vials

6. ASV Adverse Reaction Management

Reaction Type	Timing	Management
Early anaphylactic	10 min to 3 hr after starting	Inj. Adrenaline 0.5 mg IM (0.01 mg/kg in a child). Stop ASV temporarily. Oxygen. IV Hydrocortisone 200 mg. IV Chlorpheniramine 10 mg. Restart ASV slowly once stable.
Pyrogenic	1 to 2 hr after starting	Rigors, fever and hypotension from pyrogen contamination during manufacture, not from the venom or the antivenom protein itself. Treat exactly as for an anaphylactic reaction: adrenaline, oxygen, hydrocortisone, chlorpheniramine.
Late (serum sickness)	1 to 12 days after starting (mean 7)	Fever, itching, recurrent urticaria, joint and muscle pain, lymphadenopathy, and rarely immune complex nephritis or encephalopathy. Chlorpheniramine 2 mg IV every 6 hours for 5 days. If it has not settled in 24 to 48 hours, add prednisolone 5 mg every 6 hours for 5 days.

Premedication: Low-dose SC Adrenaline (0.25 mg) given 5 minutes before ASV reduces early adverse reactions.

7. Regional Considerations: Coastal Karnataka and South India

Hump-nosed Pit Viper, a small brown snake common in coastal Karnataka, not covered by Indian polyvalent ASV — Hump-nosed Pit Viper: the upturned snout is the marker

Olive Keelback, a common non-venomous snake near water that is frequently mistaken for a venomous species — Olive Keelback: non-venomous, common near water, often mistaken for one

Hump-nosed Pit Viper (Hypnale hypnale): Common in coastal Karnataka. Causes AKI and coagulopathy. Indian polyvalent ASV does NOT neutralise its venom. Management is strictly supportive.
South Indian Russell's Viper: Unique variant that causes both profound coagulopathy AND neuromuscular paralysis (ptosis). Tick the overlap checkbox on the Clinical Assessment tab if both are present.
Olive Keelback: Non-venomous, and very common near water bodies around Udupi. It is often mistaken for a venomous snake, which is a common reason for a frightened patient arriving with no envenoming at all.

8. What This Tool Does Not Print

A threshold for any laboratory value. The form takes the syndrome, the 20WBCT and the severity boxes, and no platelet count, INR or fibrinogen.
A compartment pressure. The result requires a confirmed pressure before fasciotomy and gives no number for it.
A manufacturer. The vial count is the same whichever Indian polyvalent product is on the shelf.