Snakebite ASV Protocol

1. Initial Assessment

History

• Time of bite, snake description (color, size, hood/rattle)
• Symptoms onset: local vs. systemic

Examination — Identify Envenomation Syndrome

2. Indications for ASV

Definite Indications:

• Haematotoxicity: 20-minute whole blood clotting test (20WBCT) positive; spontaneous bleeding (gum, IV site, hematuria); thrombocytopenia
• Neurotoxicity: Ptosis, ophthalmoplegia, dysarthria, dysphagia, respiratory distress
• Cardiovascular: Hypotension, shock, abnormal ECG
• Renal: Oliguria/anuria, rising creatinine
• Local envenomation (severe): Rapidly progressive swelling involving >50% of limb, necrosis, finger/toe bites with any swelling

Note: A dry bite (no envenomation) does NOT require ASV. Local swelling alone (without progression) is a relative indication.

3. 20-Minute Whole Blood Clotting Test (20WBCT)

1. Place 2 mL fresh blood in a clean, dry glass tube
2. Leave undisturbed for 20 minutes at room temperature
3. Normal: Blood clots (tube can be tilted/inverted without spillage)
4. Abnormal (Venom-Induced Consumption Coagulopathy, VICC): Blood remains liquid → ASV indicated
5. Repeat every 6 hours during monitoring

4. ASV Administration

Antivenom Type

• India: Polyvalent ASV — covers Big Four: Russell's viper, Saw-scaled viper, Common krait, Indian cobra
• Produced from horse serum (IgG/F(ab')₂ fragments)
• Monospecific ASV if offending species clearly identified (Harrison's, p. 13049)

Route

• IV only (intramuscular is NOT recommended — unreliable absorption)

Preparation

• Dilute ASV in 100–250 mL normal saline (0.9% NS)

Dosing

• Infuse slowly over 30–60 minutes (first 10–15 min at slow rate, monitoring for reactions)
• Repeat dose: Give additional 10 vials if:
  • No clinical improvement after 1–2 hours
  • 20WBCT still positive at 6 hours
  • Neurotoxic signs progress

There is no maximum total dose — give as many vials as needed to achieve clinical neutralization.

Pediatric Dosing

• Same dose as adults (venom dose is independent of patient body weight)

5. Pre-medication (Controversial)

WHO 2010 does not routinely recommend prophylaxis due to lack of evidence; have adrenaline drawn up and ready at all times.

6. Monitoring for Antivenom Reactions

Early Anaphylactic Reaction (within 10–180 min)

• Urticaria, pruritus, fever, hypotension, bronchospasm
• Action: Stop ASV infusion → Adrenaline 0.5 mg IM → Antihistamine + hydrocortisone IV → Resume at slower rate once stabilized

Pyrogenic Reaction (within 1–2 hours)

• Fever, chills, rigors
• Action: Paracetamol; cool with tepid sponging

Serum Sickness (5–14 days later)

• Fever, rash, arthralgia, lymphadenopathy
• Action: Oral prednisolone 5 mg every 6 hours × 5–7 days; antihistamines

7. Adjunct Management

Neurotoxic Bites (Krait/Cobra)

• Neostigmine test: 1.5–2 mg neostigmine IM + 0.6 mg atropine IV — if improvement in ptosis within 30 min → continue neostigmine 0.5 mg every 30 min
• Monitor respiratory rate, SpO₂; early intubation if VC <15 mL/kg or SpO₂ falling
• Mechanical ventilation may be needed for days to weeks (krait bites)

Haemotoxic Bites

• Fresh frozen plasma (FFP) or fresh whole blood if bleeding uncontrolled and ASV already given
• Do NOT give FFP before ASV — it will be consumed by ongoing coagulopathy
• Platelet transfusion only if active bleeding + severe thrombocytopenia

Local Wound Care

• Clean with antiseptic; immobilize and keep below heart level
• Tetanus prophylaxis
• Antibiotics (amoxicillin-clavulanate or ciprofloxacin) only if signs of secondary infection
• Fasciotomy: Only if confirmed compartment syndrome (not just swelling); measure compartment pressure >30 mmHg

Renal Failure

• IV fluids to maintain urine output >0.5 mL/kg/hr
• Dialysis if oliguria persists despite ASV and fluids

8. Monitoring Schedule

9. What NOT to Do

• ❌ Tourniquet (causes ischemia, worsens necrosis)
• ❌ Incision and suction of bite site
• ❌ Ice application
• ❌ Electric shock therapy
• ❌ Pressure immobilization for cytotoxic/hemotoxic bites
• ❌ Intramuscular ASV
• ❌ ASV without confirmed envenomation

Pressure immobilization bandage is appropriate ONLY for neurotoxic bites (krait, cobra, sea snake) where local effects are minimal.

10. Discharge Criteria

• 20WBCT normal on ≥2 consecutive tests
• No neurotoxic signs for 24 hours
• Urine output normal, creatinine trending down
• Local swelling stable/decreasing
• Minimum observation: 24 hours after last ASV dose