Irukandji Syndrome

Caused most commonly by the jellyfish Carukia barnesi (though other, similar small jellyfish can cause an “Irukandji-like” sting), most often in northern Australian waters. Causes delayed, severe generalised pain and — in a minority — significant cardiac involvement with cardiogenic shock and pulmonary oedema.

Clinical presentation

• Minimal initial local effects — the sting itself often goes unnoticed, especially in divers in deep water
• 20–30 minutes later, the patient develops severe generalised pain (back, abdomen, chest, muscles), tachycardia and hypertension, nausea/ vomiting, agitation and anxiety — often with a sense of impending doom
• Cardiac effects (only in severe cases): ECG changes (ST depression, T-wave inversion), elevated troponin, cardiogenic pulmonary oedema and cardiogenic shock — thought to relate to catecholamine release rather than direct cardiotoxicity

Treatment

• Transport to hospital — often requires admission for large doses of titrated opioid analgesia (e.g. IV fentanyl)
• Antiemetics (e.g. promethazine 10–25 mg) and benzodiazepines can help symptomatically; hypertension usually resolves with adequate analgesia and benzodiazepines
• All patients need an ECG and troponin — if abnormal, arrange an echocardiogram
• Cardiac monitoring, with careful evaluation for hypertensive emergencies (myocardial injury, pulmonary oedema, intracranial haemorrhage)

From Marine envenomations, Berling & Isbister, Australian Family Physician 44(1-2), 2015 (reprinted).