Irukandji syndrome

Irukandji Syndrome (Carukia barnesi)

Irukandji syndrome is a distressing envenoming secondary to the sting of Carukia barnesi and other, as yet unidentified, jellyfish found in coastal waters of tropical Australia. It has also been reported in Hawaii, the Caribbean, Asia and Papua New Guinea. In a small number of cases, life‑threatening hypertension and pulmonary oedema may develop. Two fatalities have been attributed to this condition in Australia. Management is symptomatic and supportive. Antivenom has not yet been developed.

Toxin

The composition and mechanism of action of Irukandji venom has not been fully characterised but is thought to act as a pre-synaptic sodium channel agonist, inducing massive catecholamine release.

Clinical presentation and course

• The initial sting is usually not felt and there is a short delay to the onset of systemic symptoms. Local signs, such as welts or dermal markings, are minimal or absent
• Multiple systemic symptoms develop from 30–120 minutes after contact with the jellyfish. These include a sense of impending doom, agitation, dysphoria, vomiting, generalised sweating and severe pain in the back, limbs or abdomen. Hypertension and tachycardia are common.
• Symptoms usually settle within 12 hours
• Severe envenoming manifests within 4 hours with on‑going significant opioid requirements. These patients are at risk of toxic cardiomyopathy, cardiogenic shock and pulmonary oedema and may require intubation and mechanical ventilation
• Intracerebral haemorrhage occurred in two patients within 3–4hours of the sting, presumably due to uncontrolled hypertension.

Management

• Apply generous volumes of vinegar to all visible sting sites to inactivate all undischarged nematocysts (sting cells)
• Do not apply a pressure immobilisation bandage (PIB)
• Transport all patients with pain refractory to first‑aid, or systemic symptoms to a medical facility – this is a potentially life‑threatening emergency

Potential early life‑threats that require immediate interventions include:

• Severe hypertension
• Pulmonary oedema

Treatment

• Administer IV fentanyl (0.5–1.0 microgram/kg/dose) repeated every 10 minutes until appropriate analgesia is achieved. Large doses may be required (e.g. 200–300 microgram). Note: If fentanyl is not available, give morphine 0.1 mg/kg IV in titrated doses
• Treat nausea with IV promethazine (25 mg; 0.5 mg/kg in children)
• Control hypertension refractory to opioid analgesia with an intravenous infusion of glyceryl trinitrate (50 mg in 100 mL starting at 6 mL/minute; 1–4 microgram/kg/minute in children) titrated to achieve a systolic blood pressure <160 mmHg
• Manage pain refractory to opioids with IV magnesium (0.2 mmol/kg up to 10 mmol in adults) administered over 5–15 minutes. Seek expert advice

Antivenom

• None available.

Differential diagnosis

• Envenoming by the box jellyfish (Chironex fleckeri) is associated with immediate pain and obvious dermal markings (large welts). Tentacles may be seen adherent to the skin
• Bluebottle stings (Physalia species) are associated with immediate pain and dermal markings. The pain usually resolves within 1 hour and systemic symptoms are extremely rare
• Decompression illness may lead to generalised pain or collapse shortly after a diver has surfaced. Welts are not seen
• Redback spider envenoming (Latrodectus hasseltii) causes bite site pain and sweating, followed by more generalised pain, sweating and dysphoria. It is associated with contact with a spider on land.

Handy tips

• Clinical features of envenoming occur after the patient has left the water, so they may be unaware they have been stung
• Irukandji syndrome should be considered in any patient presenting with clinical features during or shortly after swimming in tropical coastal Australian waters
• Clinical features of dysphoria, severe generalised pain, sweating, hypertension and pulmonary oedema, in the absence of major dermal findings, is pathognomic of irukandji syndrome
• Patient controlled analgesia may be useful where there is an on‑going opioid requirement.

References

• Armstrong J, Pascu O. Irukandji Syndrome, Toxicology Handbook Australia 4e, Elsevier 2022; 501-503
• Jack Barnes and the Irukandji Enigma
• Tox Conundrum 008 – Irukandji case 1
• Tox Conundrum 009 – Irukandji case 2
• Nickson CP, Waugh EB, Jacups SP, Currie BJ. Irukandji syndrome case series from Australia’s Tropical Northern Territory. Ann Emerg Med. 2009 Sep;54(3):395-403.