Table 1.

Treatment of early antivenom reactions and anaphylaxis consistent with the World Allergy Organization Anaphylaxis Guidelines

Mild immediate antivenom reactions: (rash, flushing, gastrointestinal effects)
Some mild reactions resolve with temporary cessation of the antivenom infusion and recommencing it at a slower rate.
Severe anaphylaxis (sudden hypotension, bronchospasm): Initial management
Suspend the antivenom infusion. Lie the patient flat (if not already), commence high flow or 100% oxygen and support airway and ventilate patient as required. Commence a rapid infusion of 1000 ml normal saline (20 ml kg–1 in children) over 2 to 3 min. Administer adrenaline i.m. into the lateral thigh, 0.01 mg kg–1 to maximum of 0.3 mg (alternatively, those experienced with i.v. adrenaline infusions may proceed directly to this, as below*).
Severe anaphylaxis: Unresponsive to initial management:
If hypotensive, repeat normal saline bolus as above (up to 50 ml kg–1 may be required). Commence i.v. infusion of adrenaline (0.5–1 ml kg–1 h–1, of 1 mg in 100 ml) and titrate according to response; monitor blood pressure every 3 to 5 min; beware that as the reaction resolves adrenaline requirements will fall, the blood pressure will rise and the infusion rate will need to be reduced. Consider nebulized salbutamol for bronchospasm, nebulized adrenaline for upper airway obstruction and i.v. atropine for severe bradycardia.

^*Envenomed patients may be severely coagulopathic, so it is important to be cautious when giving adrenaline to avoid blood pressure surges, which might lead to intracerebral haemorrhage.