CSL Antivenom Handbook

CSL Box Jellyfish Antivenom

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Basic Information

Used for neutralising envenoming by the major Australian box jellyfish (=sea wasp), Chironex fleckeri. It is made from sheep IgG. Each ampoule contains 20,000 units of neutralising capacity against the target venoms. Average volume per ampoule is 1.5-4mL. The immunising species is the box jellyfish, Chironex fleckeri.

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Information about the jellyfish covered by this antivenom

The species

Chirodropids (eg Chironex fleckeri) are large, tropical virtually transparent jellyfish, with an approximately square shaped body, with tentacles draping from each of the four corners. Each tentacle contains millions of individual stinging cells, nematocysts, each of which can deliver venom via an everting stinging device. A proportion of this venom may be injected into capillaries just beneath the skin surface. This explains the very rapid development of severe systemic envenoming in major box jellyfish stings. A number of other box jellyfish species occur in Australian coastal waters but none has been definitely associated with fatal envenoming.

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Chirodropids (eg Chironex fleckeri) are confined to tropical Australian waters, including offshore islands, where they are found year round, but are most commonly encountered in the summer months and near outflows from estuaries.

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Venom composition

The venom is multicomponent and difficult to collect, so is incompletely understood. It has components which can cause local pain and necrosis, and in high doses, components that can affect cardiac function and respiration.

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Clinical effects

The extent of envenoming by Chirodropids (eg Chironex fleckeri) is essentially dependent on the area of discharging tentacle contact. Involvement covering > 10% of total skin area is a potentially lethal envenoming especially in children. Systemic envenoming in such cases can occur within minutes of the sting, with cardiac dysfunction or arrest possible within 5 mins after a major sting. This emphasises the importance of rapid effective first aid.

At every point of skin contact with tentacles there will be immediate excruciating pain, usually with linear red whelts. These affected areas of skin may go on to develop blistering and/or necrosis. Incoherence due to pain may occur. Shortly after, in severe stings, there may be the cardiac problems mentioned earlier. Respiratory dysfunction may occur later, sometimes associated with pulmonary oedema, but a central respiratory depressant effect has also been suggested.

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When to use this antivenom, how much to use and how to give it

CSL Box Jellyfish Antivenom should be given as soon as possible if there is evidence of life threatening envenoming, such as collapse or cardiac dysfunction /arrest (3 vials recommended). See potential contraindications. It should ideally be given intravenously, through a drip set, but speed is of the essence in severe envenoming and it has proved efficacious and safe, given IM on the beach or in the ambulance, by paramedical staff. In a situation of persisting collapse or life threatening cardiac dysfunction/arrest, up to 6 vials of antivenom may be given consecutively IV (preferably diluted). Other indications for antivenom are severe pain, persisting despite cold packs and parenteral narcotics and a potential but unproven benefit to cosmetic outcome. Again, ideally, prior to commencing antivenom therapy, make sure everything is ready to treat anaphylaxis, should this occur. In practice, however, anaphylaxis has not yet resulted with this antivenom, and the need for early administration in severe cases may well outweigh the need to be fully prepared to treat anaphylaxis.

The use of adrenaline as pre-treatment when using antivenoms is still being debated. The risk of anaphylaxis varies from antivenom to antivenom. It is recommended that the Product Information be read before use and if necessary contact be made with a specialist in the field.

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What to do if there is an immediate untoward reaction to the antivenom

If there is either a sudden fall in blood pressure or bronchospasm, after starting the antivenom infusion and clearly due to an adverse reaction to antivenom rather than an effect of the venom, then temporarily stop the antivenom and give adrenaline by subcutaneous injection, give 100% O2 and IV fluids (Haemaccel®). Once the untoward antivenom reaction is thus controlled, cautiously recommence antivenom infusion.

If adrenaline is to be given (by subcutaneous injection), use a 1:1000 solution. For adults give 0.5mL (0.5mg) initially. For children give 0.01mg/kg initially. Repeat as necessary and try IM injection if no response to SC injection. If bronchospasm is the major problem, try nebulised adrenaline, 2mL of 1:1000 solution.

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What to do prior to discharge

Any patient who has received antivenom may develop serum sickness, from 4 to 14 days later. Before leaving hospital, they should be advised of the symptoms of serum sickness, such as rash, fever, joint aches and pains, malaise, and told to return immediately for review and probable commencement of oral steroid therapy. If there was major envenoming, organise follow up. This is usually not necessary for minor envenoming.

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