Box jellyfish sting — OSCE

Station brief (8–10 minutes)

A 5-year-old girl is brought to a north Queensland emergency department ten minutes after wading at a beach in the stinger season. She has severe immediate pain and angry whip-like, cross-hatched skin lesions across both legs, with tentacle fragments still adherent. She is becoming pale and drowsy, with a weak pulse and a blood pressure that has fallen to seventy over forty. You are the registrar leading the resuscitation, with a skilled nurse and a junior doctor present. Run the first aid, give the correct antivenom, and resuscitate while retrieval is arranged. Name the source for each threshold. [9] [11]

Tasks for the candidate

1. State the immediate first aid for the adherent tentacles and name what must never be done. [9]
2. Describe the resuscitation of the cardiorespiratory compromise and the indication for box jellyfish antivenom. [9]
3. Distinguish this sting from the Irukandji syndrome and the bluebottle sting by first aid. [10] [11]
4. Outline the analgesia, monitoring and disposition after initial stabilisation. [12]
5. State the prevention advice for families in the tropical stinger season. [9]

Expected performance

Must hit. Recognises a box jellyfish (Chironex fleckeri) sting from the immediate agonising pain, the whip-like cross-hatched skin lesions and the tropical stinger-season setting. Douses the adherent tentacles with vinegar (four to six per cent acetic acid) for at least thirty seconds to deactivate undischarged nematocysts, then carefully lifts the tentacles off. States explicitly that the area is not rubbed and that fresh water is never used, because it triggers further nematocyst discharge. Runs the airway, breathing and circulation resuscitation — oxygen, bag-mask ventilation, cardiac monitoring, intravenous or intraosseous access, and a fluid bolus — and, because the child is hypotensive and drowsy with cardiorespiratory compromise, gives box jellyfish antivenom intravenously, considering magnesium for the failing heart, and continues high-quality cardiopulmonary resuscitation because the venom is cardiotoxic and recovery is possible. [9]

Merit. Contrasts the box jellyfish sting with the Irukandji syndrome, which presents twenty to forty minutes after a trivial carybdeid sting with severe generalised pain, sweating and hypertension, and which takes the same vinegar first aid but has no specific antivenom and is managed supportively with opioid analgesia and cardiac monitoring; and with the bluebottle, which takes hot water at about forty-five degrees for up to twenty minutes rather than vinegar. Anticipates troponin rise, pulmonary oedema and dysfunction, gives generous opioid analgesia, and arranges paediatric intensive care retrieval with the airway secured. Names the prevention advice — swim inside stinger nets, wear protective clothing, and heed the stinger-season warnings. [10] [11]

Fail. Uses fresh water or rubs the sting; uses hot water instead of vinegar for the box jellyfish; withholds box jellyfish antivenom in a child with cardiorespiratory compromise; fails to resuscitate or arrange intensive care; or confuses the box jellyfish with the Irukandji syndrome or the bluebottle. [9] [11]

Sample candidate structure

"This is a box jellyfish sting — the immediate severe pain, the whip-like cross-hatched skin lesions and the tropical stinger season make this the most venomous marine sting, capable of killing a small child within minutes. I douse the adherent tentacles with vinegar for at least thirty seconds to deactivate the nematocysts, then carefully lift them off — I do not rub and I never use fresh water. She is hypotensive and drowsy with cardiorespiratory compromise, so I give oxygen, bag-mask ventilation, a fluid bolus, and intravenous box jellyfish antivenom, with magnesium considered for the failing heart, and I continue high-quality cardiopulmonary resuscitation. I distinguish this from the Irukandji syndrome, which is delayed and catecholaminergic, and from the bluebottle, which takes hot water. I give opioid analgesia, monitor the troponin, and arrange paediatric intensive care retrieval, and I counsel the family on stinger-season prevention." [9] [12]