How to administer Anti-Snake Venom (ASV)

Administration of Anti-Snake Venom (ASV)

Anti-snake venom should be administered intravenously as an initial dose of 4-6 vials as soon as possible after envenomation, followed by additional doses until initial control of symptoms and laboratory parameters is achieved. 1

Initial Assessment and Preparation

• Activate emergency services immediately for any person bitten by a venomous or possibly venomous snake
• Rest and immobilize the bitten extremity to minimize venom spread
• Remove constricting objects (rings, jewelry) from the bitten extremity to prevent further injury as swelling progresses

ASV Administration Protocol

Pre-administration Testing

• Skin testing is NOT recommended before ASV administration due to poor predictive value for allergic reactions 2
• Studies of equine-derived antitoxins show that skin testing has low positive predictive value (averaging 32%) for immediate-type hypersensitivity reactions 2

Dosing Guidelines

1. Initial Dose:

   • Administer 4-6 vials of ASV intravenously as soon as possible after envenomation 1
   • For severe envenomation with incoagulable blood, consider higher initial doses of 10-20 vials 3, 4

2. Subsequent Dosing:

   • Continue administration until initial control of symptoms is achieved
   • Monitor coagulation parameters (clotting time) every 6 hours 4
   • Additional doses of 50-100ml (typically 5-10 vials) may be required if coagulation abnormalities persist 4

3. Total Dosage:

   • Total ASV requirement correlates with severity of initial coagulation dysfunction 4
   • Recent studies suggest that low-dose regimens (total of 4-7 vials) may be as effective as high-dose regimens (≥10 vials) with comparable outcomes and fewer adverse effects 5, 6

Administration Technique

1. Preparation:

   • Use a 1-mL syringe with a 26- to 27-gauge half-inch non-removable needle for administration 2
   • ASV should be given intravenously (IV) for snake envenomation

2. Administration Method:

   • Administer by slow IV infusion after dilution in 100-200ml of normal saline
   • Monitor vital signs closely during administration
   • Have emergency medications and equipment ready to treat potential allergic reactions

Monitoring and Follow-up

• Monitor for recurrence of coagulation dysfunction even after initial correction (occurs in approximately 35% of cases) 4
• Continue clotting time monitoring every 6 hours for at least 24-48 hours after normalization
• Monitor for development of acute kidney injury, which may occur in 10-20% of patients 6

Management of Adverse Reactions

• Allergic reactions to ASV occur in approximately 1-2% of patients 2
• If allergic reaction occurs:
  • Stop ASV infusion immediately
  • Administer epinephrine 0.01 mg/kg of 1:1000 solution (maximum: 0.3-0.5 mg) IM 2
  • Consider antihistamines and corticosteroids as adjunctive therapy
  • After stabilization, consider resuming ASV at a slower infusion rate with close monitoring

Special Considerations

• Timing is critical: Early administration of ASV (within the "golden hours") is essential to prevent irreversible venom-mediated effects 7
• Location of administration: ASV should ideally be administered in a healthcare facility with capacity to manage potential adverse reactions 2
• Pediatric dosing: Children receive the same dose of ASV as adults, as the amount of venom injected by the snake is the same regardless of the victim's size

Pitfalls to Avoid

• Do not delay ASV administration for skin testing, as this has poor predictive value and wastes critical time 2
• Do not apply tourniquets, ice, electric shock, or suction devices to the bite site 2, 1
• Do not use pressure immobilization bandaging for North American pit viper bites 2, 1
• Do not administer ASV intramuscularly as this can lead to unpredictable absorption and potential tissue damage

Early administration of appropriate doses of ASV remains the cornerstone of treatment for venomous snakebites, with evidence suggesting that both the timing of administration and appropriate dosing are critical factors in determining outcomes.