CSL Antivenom Handbook

CSL Sea Snake Antivenom

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Basic Information

Used for neutralising systemic envenoming by all species of sea snakes. It is made from horse IgG. Each ampoule contains 1000 units of neutralising capacity against the target venoms. Average volume per ampoule is 15-35mL. The immunising species are the beaked sea snake, Enhydrina schistosa and the Australian tiger snake, Notechis scutatus. The antivenom has been shown to be effective, to varying degrees, in neutralising a wide variety of sea snake venoms, including olive sea snake Aipysurus laevis, Stoke's sea snake Astrotia stokesii, olive headed sea snake Disteira (Hydrophis) major, banded sea snake Hydrophis cyanocinctus, elegant sea snake Hydrophis elegans, Daudin's sea snake Hydrophis nigrocinctus, narrow banded sea snake Hydrophis spiralis, Gunther's sea snake Hydrophis stricticollis, spine-bellied sea snake Lapemis hardwickii, banded sea krait Laticauda semifasciata and needle-headed sea snake Microcephalophis gracilis.

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Information about the snakes covered by this antivenom

 The species

There are 31 species of sea snake in northern Australian waters alone. All are possibly dangerous to humans, but relatively few of these have caused bites of significance. Sea snakes are closely related to the venomous Australian land snakes of the family Elapidae, but are currently classified in a separate family, Hydrophiidae. Two subfamilies have been listed in the past, the sea kraits, Laticaudinae, and the true sea snakes, Hydrophiinae, though recent work suggests this subfamilial division may be inappropriate. All spend some (sea kraits) or all (sea snakes) of their life in the sea. Most are fish eaters. They may be inquisitive but are not usually aggressive unless threatened, such as when caught in a fishing net. A description of all species is clearly beyond the scope of this publication.

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Sea snakes are found predominantly in the northern waters of Australia, though storms may carry the occasional specimen southward, with authenticated bites from Sydney. They are not likely to be found in waters off the southern coast of Australia, where alleged sea snake bites are essentially always due to some other organism, usually an eel.

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Venom composition

Sea snake venoms have been the subject of much research, because of their post synaptic neurotoxins, many of which have been sequenced. The other important component of some sea snake venoms is myotoxin, which may dominate the clinical picture.

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Clinical effects

Sea snake bite is usually felt, with small but distinct teeth marks visible, which may be multiple, mostly from non-fang teeth. Pain at the bite site is not a major feature, nor swelling. The important effects, seen in only some cases, are systemic, either paralysis and/or myolysis. If envenoming has occurred, then one of these latter two effects may be expected within 6 hours in most cases, manifested as either early paralysis (eg ptosis, ophthalmoplegia, limb or respiratory weakness) or myolysis (eg myoglobinuria, muscle pain and weakness). Secondary kidney damage may occur if there is major myolysis and there may also be severe hyperkalaemia. Coagulopathy is not seen.

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

As with most antivenoms, CSL Sea Snake Antivenom should only be given if there is clear evidence of envenoming. See potential contraindications. It should be given intravenously, through a drip set. If possible, dilute antivenom up to 1 in 10, with an isotonic crystaloid solution (eg saline, Hartmans or dextrose). In general, each ampoule/dose should be run over 15-30 minutes. Prior to commencing antivenom therapy, make sure everything is ready to treat anaphylaxis, should this occur. Specifically, have adrenaline ready to give. If there is an infusion pump available, have this set up to run through a side arm of the drip set, with a solution of dilute adrenaline (eg 6mg adrenaline in 100mL of saline or 5% dextrose, or equivalent dilution). Clearly mark this pump, so that it is not accidentally started.

The use of adrenaline as pre-treatment when using antivenoms is still being debated. The risk of anaphylaxis varies from antivenom to antivenom. People who have had previous exposure to equine derived products may be at greater risk. It is recommended that the Product Information be read before use and if necessary contact be made with a specialist in the field.

If there is evidence of either paralysis or myolysis then the patient should receive antivenom. CSL Sea Snake Antivenom is the first choice, starting with an initial dose of 1 to 3 vials, depending on the severity and rapidity of onset of envenoming. Up to 10 vials have been used in severe cases. If CSL Sea Snake Antivenom is either not available, or inadequate stocks are to hand, then CSL Tiger Snake Antivenom may be used; as a rough guide, 1 vial of CSL Sea Snake Antivenom is equivalent to 2 to 4 vial of CSL Tiger Snake Antivenom. CSL Polyvalent snake antivenom may be used if no sea snake or tiger snake antivenom is available.

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

(This section is common to most antivenoms)

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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. If several bottles of antivenom have been given to the patient (eg >2) it may be useful to give a 5 day course of oral steroids as prophylaxis for serum sickness (eg 30-50mg daily of prednisolone, for adults).

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