- Clinical evidence of envenomation including neurotoxicity (paralysis and respiratory failure)
- Laboratory evidence of myotoxicity within 6 hours of the bite
- No absolute
- Increased Risk of anaphylaxis in patients previously treated with antivenom or those who are suspected of equine sera allergy
- Place the patient in a monitored area where anaphylaxis can be managed.
- Administer 1 ampoule diluted in 500ml of 0.9% saline IV over 20 minutes (the dose is the same for adults and paediatrics – snakes don’t envenomate less because its a child).
- If there is progressive neurological deterioration then 3 ampoules of antivenom should be given.
- Normally one ampoule is sufficient to halt the progression of the paralysis, careful observation is required following the initial dose including spirometry and peak flow measurements.
- Antivenom can be given as a rapid IV push in patients who are unstable or in cardiac arrest.
Adverse drug reactions:
- Anaphylaxis: Cease antivenom infusion, treat as per anaphylaxis with oxygen, IV fluids and IM adrenaline. Recommence antivenom infusion when anaphylaxis has resolved. Rarely will ongoing administration of adrenaline be required to complete the antivenom infusion.
- Serum Sickness: A benign and self limiting complication occurs 5-10 days after antivenom, symptoms include fever, rash, arthralgia and myalgia. Oral steroids for 5 days may ameliorate symptoms (e.g. prednisolone 50mg/day in adults and 1mg/kg in children). All patients should be warned about this complication who receive antivenom.
- The use of other antivenoms e.g. Polyvalent has been used historically but there is no data to support this practice.
- White J. A clinician’s guide to Australian venomous bites and stings: Incorporating the updated CSL antivenom handbook. Melbourne: CSL Ltd, 2012.