Vasculotoxic Snakebite: Treatment

Overview

• Local tissue destruction, edema, and necrosis
• Venom-induced consumption coagulopathy (VICC) / DIC
• Thrombocytopenia
• Hemolysis and hemoglobinuria
• Acute kidney injury (AKI)

Clinical Features

Extensive tissue necrosis and dry gangrene following vasculotoxic pit viper bite — demonstrates the importance of early antivenom.

First Aid (Pre-hospital)

• Immobilize the bitten limb below heart level (reduces venom spread)
• Remove rings, watches, tight clothing
• Do NOT: cut/suck the wound, apply tourniquet, apply ice, give aspirin/NSAIDs
• Transport urgently to a hospital with antivenom

Hospital Management

1. Antivenom (Cornerstone of Treatment)

• Coagulopathy (elevated PT/aPTT, low fibrinogen, thrombocytopenia)
• Active hemorrhage
• Progressive local swelling beyond the bitten limb
• Hemodynamic instability
• Hemolysis or hemoglobinuria

2. Coagulopathy Management

• Baseline labs: PT, aPTT, fibrinogen, platelet count, D-dimer, CBC, blood group
• Antivenom is the definitive treatment for VICC — not FFP alone
• Fresh Frozen Plasma (FFP) or cryoprecipitate: indicated for active bleeding with coagulopathy; do NOT give prophylactically without antivenom (replenished clotting factors are quickly consumed)
• Platelet transfusion: if platelets <20,000 with active bleeding
• Avoid: heparin (worsens bleeding), aspirin, NSAIDs

3. Fluid Resuscitation

• IV crystalloids (0.9% NaCl or Ringer's lactate) for hypotension/shock
• Urine output monitoring (target ≥0.5 mL/kg/hr) to prevent oliguric AKI

4. Renal Protection

• Aggressive hydration to prevent myoglobin/hemoglobin cast nephropathy
• Urinary alkalinization (sodium bicarbonate) if hemoglobinuria is present
• Dialysis (hemodialysis) if AKI with oliguria/hyperkalemia/uremia occurs

5. Local Wound Care

• Elevate the limb
• Monitor for compartment syndrome (tense compartments, pain on passive stretch) — requires fasciotomy (though debated; antivenom is preferred first)
• Debridement of necrotic tissue after stabilization
• Tetanus prophylaxis
• Antibiotics: only if secondary infection is confirmed (prophylactic antibiotics are not routinely recommended)
• Surgical amputation may be required in cases of extensive necrosis/gangrene (as illustrated above)

6. Monitoring

Special Situations

Common Vasculotoxic Snakes by Region

Anti-Snake Venom (ASV): Dosing & Duration

General Principles

• Dose is based on venom load, not patient body weight — children receive the same dose as adults
• The goal is to neutralize all circulating venom; undertreating is more dangerous than overtreating
• Antivenom should be species-specific (monospecific) or regionally appropriate (polyspecific)
• The treating physician at bedside must be present during infusion for early detection of anaphylaxis

Indian Polyvalent ASV (Most Widely Used in South Asia)

Initial Dose

WHO recommendation: Initial dose of 10 vials IV for systemic envenomation; reassess at 6 hours.

Repeat Dosing Criteria

• Coagulopathy not correcting (20-minute Whole Blood Clotting Test [20WBCT] still non-clotting)
• Ongoing active bleeding
• Progressive local swelling
• Worsening neurological signs
• Persistent hypotension/shock

20-Minute Whole Blood Clotting Test (20WBCT)

1. Place 2 mL of fresh venous blood in a clean, dry glass tube
2. Leave undisturbed at room temperature for 20 minutes
3. Tilt the tube:
   • Clot formed → coagulopathy resolved, no further ASV needed
   • No clot (non-clotting blood) → active VICC, repeat ASV dose

Crotalidae Polyvalent Immune Fab — CroFab (North American Pit Vipers)

North American Coral Snake Antivenom

• Dilute 3–5 reconstituted vials in 250–500 mL normal saline
• Infuse IV over 1 hour (provider must remain at bedside)
• If signs of envenomation progress despite initial dosing: repeat starting dose
• Up to 10 vials total may be required

Duration of ASV Treatment

Administration Protocol Summary

1. Pre-medicate: Adrenaline 0.25 mg SC (optional but widely practiced)
2. Dilute ASV in NS (250–500 mL)
3. Start infusion slowly (1 mL/min × 10 min)
4. Observe for anaphylaxis: urticaria, hypotension, bronchospasm
5. If no reaction → increase to full infusion rate over 60 min
6. Reassess at 6 hours with 20WBCT + clinical exam
7. Repeat dose if criteria met (see above)
8. Continue 6-hourly reassessment until stable

Anaphylaxis During Infusion

Key Points

• Never give ASV IM for systemic envenomation (absorption is unreliable)
• Pediatric dose = adult dose (same venom load regardless of body weight)
• FFP/cryoprecipitate should be given only after antivenom (otherwise clotting factors are rapidly consumed by residual venom)
• No upper limit is absolute — continue until clinical and laboratory endpoints are met