Australian snake bite with coagulopathy and collapse
The case
A 47-year-old sheep farmer from central New South Wales presents to a regional emergency department 50 minutes after being bitten on the right ankle at dusk. He felt two small punctures with mild local pain. On the way he developed nausea, vomiting and light-headedness, and the ambulance recorded an episode of collapse. Blood pressure is 82/50 mmHg, heart rate 110/min and respiratory rate 20/min; he is sweaty. There are two puncture marks with minimal swelling. Neurological examination is normal. INR is 3.1 (0.8–1.2), fibrinogen 0.7 g/L (2.0–4.0), platelets 140 × 10^9/L (150–400), creatinine 92 micromol/L and CK 220 U/L. What is the single best next step in management?
Options
- AGive intravenous antivenom without delay
- BObserve and repeat coagulation studies
- CGive neostigmine and atropine slowly
- DGive fresh frozen plasma to correct the INR
- EApply a proximal arterial tourniquet
Think it through before you read on. Which single option is best, and why are the other four wrong?
Show the answer and explanation
Answer
A. Give intravenous antivenom without delay
Why this is the right answer
This man has systemic envenoming. Collapse, hypotension and a consumptive coagulopathy (raised INR, very low fibrinogen) after a snake bite in rural New South Wales point to a brown snake, the commonest cause of serious envenoming and death in Australia. Venom-induced consumption coagulopathy can lead to fatal bleeding, and early collapse is a marker of severe envenoming.
Antivenom is the only treatment that neutralises circulating venom, and it should be given as soon as systemic envenoming is confirmed. Therapeutic Guidelines (Toxicology and Toxinology) and the Australian Resuscitation Council guideline are clear that antivenom must not be delayed for further tests once the diagnosis is made. In NSW, where the snake is unidentified, a venom detection kit on the bite site can guide the choice between brown and tiger snake antivenom; if the patient is critically ill, polyvalent antivenom or both monovalent antivenoms can be given. One vial is now considered sufficient for most envenomings.
Antivenom is given intravenously, diluted, over 15 to 30 minutes, with adrenaline (epinephrine), oxygen and resuscitation equipment ready in case of anaphylaxis.
Supportive care runs in parallel: intravenous fluids for hypotension, and monitoring for bleeding. Clotting factor replacement may be considered after antivenom in patients who are bleeding, but giving plasma first is pointless because the venom will consume it.
First aid for Australian snake bite is a pressure immobilisation bandage over the whole limb with the patient kept still. It is left on until antivenom is available. Arterial tourniquets are never used.
Why the other options are wrong
- B
Waiting to watch a trend in a shocked, coagulopathic patient risks fatal haemorrhage.
- C
Neostigmine has no established role in snake bite in this country, and it does nothing for coagulopathy or shock.
- D
Plasma given before antivenom is consumed by circulating venom; antivenom first, factors later if still bleeding.
- E
Tourniquets cause limb damage and are contraindicated; the correct first aid is a pressure immobilisation bandage.
High-yield takeaway
Systemic envenoming (collapse, coagulopathy, paralysis or myolysis) means intravenous antivenom now, with adrenaline drawn up; never delay it for repeat tests or plasma.
Reference: Therapeutic Guidelines: Toxicology and Toxinology, Snake bite (and ARC Guideline 9.4.8) (2023)
Common questions
What is the correct first aid for a snake bite?
A firm pressure bandage over the whole limb, splint it, and keep the patient completely still. No tourniquet, no washing the wound, no cutting.
Is fresh frozen plasma useful in snake envenoming?
Only after antivenom, and only if the patient is still bleeding. Given first, it is simply consumed by the venom.
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