What is the recommended dose of Anti-Snake Venom (ASV) vials for treating a snake bite?

Recommended Dosage of Anti-Snake Venom (ASV) for Snake Bite Management

The initial recommended dose of Anti-Snake Venom (ASV) is 4-6 vials, followed by additional doses until initial control of envenomation is achieved. 1

Initial Management and Dosing

• The definitive treatment for snake envenomation is antivenom, which is only available in hospital settings
• Initial dosing should be:
  • 4-6 vials administered as soon as possible after envenomation
  • Additional doses should be given until initial control of symptoms is achieved
  • Dosing should be guided by clinical severity and response to treatment

Dosing Based on Envenomation Severity

The appropriate ASV dosage varies based on the severity of envenomation:

1. Mild Envenomation:

   • Lower doses may be effective (approximately 130 ml or 13 vials) 2
   • Continuous infusion regimens may be more efficient than intermittent bolus dosing

2. Moderate to Severe Envenomation:

   • Higher doses are typically required
   • For neurotoxic envenomation, the national protocol recommends a maximum dose of 200 ml (20 vials) 3
   • For hemotoxic envenomation, doses ranging from 180-230 ml (18-23 vials) may be required 2

Administration Methods

Two approaches to ASV administration have been studied:

1. Conventional High-Dose Intermittent Bolus Method:

   • Initial bolus of 100 ml (10 vials)
   • Followed by 50 ml (5 vials) every six hours until coagulation normalizes
   • May require higher total ASV amounts (up to 430 ml or 43 vials in severe cases) 2

2. Low-Dose Continuous Infusion Method:

   • Initial loading dose of 30-70 ml (3-7 vials)
   • Followed by continuous infusion of 30 ml (3 vials) every six hours
   • Continues until clinical parameters normalize
   • May reduce total ASV requirements while maintaining efficacy 2

Important Considerations

• ASV should be stocked in sufficient quantities to treat at least one 100-kg patient for 8-24 hours 4
• Hospitals in areas endemic for venomous snakes should consider stocking larger quantities based on local risk assessment 4
• The type of snake and venom (hemotoxic vs. neurotoxic) affects dosing requirements and clinical approach
• Some patients with neurotoxic envenomation may require very high doses of ASV for symptom reversal 5

Monitoring and Follow-up

• Monitor for:
  • Coagulation parameters
  • Neurological symptoms
  • Renal function
  • Signs of allergic reactions to ASV
• Recurrence of venom effects may occur due to continued venom absorption, requiring additional ASV doses 6
• Mechanical ventilation may be required in cases of neurotoxic envenomation (76.4% of cases in one study) 3

Pitfalls to Avoid

• Avoid ineffective and potentially harmful first-aid techniques such as:
  • Arterial tourniquets
  • Ice application
  • Wound incisions
  • Electric shock
  • Pressure immobilization bandaging (for North American pit vipers) 1, 7
• Do not delay ASV administration when indicated, as it is the definitive treatment
• Be aware that recurrence of symptoms may occur even after initial improvement, requiring continued monitoring and potentially additional ASV

The evidence suggests that lower-dose continuous infusion regimens may be as effective as high-dose intermittent bolus regimens while using less total ASV, but treatment should always be guided by clinical response and local protocols.