What is the standard protocol for administering Antivenom Serum (ASV) in Normal Saline (NS)?

Administration of Antivenom Serum (ASV) in Normal Saline

The standard protocol for administering Antivenom Serum (ASV) is to dilute it in normal saline (NS) and administer as an intravenous infusion, with careful monitoring for infusion reactions.

Preparation of ASV

• ASV should be reconstituted according to manufacturer's instructions if in lyophilized (powder) form
• Dilute the required number of vials in 500 ml of normal saline for adults 1
• For pediatric patients, use a smaller volume of normal saline that is appropriate for the child's size
• Use sterile technique during preparation 1
• Ensure proper labeling of the infusion with drug name, concentration, and date 1

Administration Protocol

Initial Administration

1. Establish secure intravenous access, preferably with a large-bore cannula
2. Start infusion at a slow rate for the first 10-15 minutes (approximately 15-20 drops/minute)
3. Monitor patient closely during this initial period as most severe reactions occur within the first 10 minutes 1
4. If no reaction occurs, gradually increase the rate to complete the infusion over 1 hour

Monitoring During Administration

• Continuous monitoring of vital signs (blood pressure, pulse, respiratory rate, oxygen saturation)
• Observe for signs of hypersensitivity reactions:
  • Mild: Pruritus, flushing, urticaria, chest tightness
  • Moderate: Transient cough, shortness of breath, tachycardia, hypotension
  • Severe: Loss of consciousness, severe hypotension, airway angioedema 1

Management of Infusion Reactions

If a reaction occurs:

1. STOP the infusion immediately
2. Maintain IV access with normal saline at keep-vein-open (KVO) rate
3. Notify physician and perform physical assessment
4. Administer appropriate medications based on severity:

For Mild Reactions:

• Antihistamine (Diphenhydramine 25-50 mg IV/PO)
• Consider slowing infusion rate when restarted

For Moderate to Severe Reactions:

• Administer epinephrine 0.3-0.5 mg (0.3-0.5 ml of 1:1000) IM into the mid-outer thigh for adults
• For children: 0.01 mg/kg (maximum 0.3 mg) 2
• Position patient supine with legs elevated if hypotensive
• Administer IV fluids (NS bolus 1000-2000 ml) for hypotension
• Consider corticosteroids (Hydrocortisone 100-500 mg IV)
• For respiratory symptoms, consider albuterol nebulizer 1, 2

Special Considerations

• Keep emergency medications and equipment readily available during ASV administration
• For high-dose ASV administration (as may be required in severe envenomation), continue to use the same dilution protocol but monitor more frequently 3
• The total number of vials required depends on the severity of envenomation and clinical response
• In case of 76 vials (as mentioned in the question), divide into multiple infusions of 500 ml NS each to avoid fluid overload
• Recurrence of symptoms may occur after initial improvement, requiring additional ASV administration 4

Common Pitfalls to Avoid

1. Delayed administration: Early administration of ASV is critical for preventing irreversible venom effects 5
2. Inadequate dilution: Always dilute ASV properly in NS to reduce risk of reactions
3. Rapid infusion: Administering too quickly increases risk of severe reactions
4. Inadequate monitoring: Close observation is essential during the entire infusion
5. Premature discontinuation: Complete the full course even if symptoms improve
6. Failure to prepare for reactions: Always have epinephrine and resuscitation equipment ready

By following this protocol, ASV can be administered safely and effectively to manage snake envenomation while minimizing the risk of adverse reactions.