Answer: 2 – Irukandji Jellyfish (Carukia barnesi)

What is Irukandji Syndrome [1-4]?

• Irukandji Syndrome is a sensation of extreme pain and agitation and a feeling of impending doom following envenomation by the Irukandji jellyfish and associated species.
• This jellyfish is most commonly found in Northern Australia but the syndrome has been described throughout the tropics, including Hawaii and northern Florida.
• The jellyfish is small (5 mm body with up to 100 cm long tentacles) and may not be noticed by the swimmer.
• Its venom is delivered via nematocysts and is thought to cause toxic modulation of neuronal sodium channels leading to excessive catecholamine release.

What is the clinical presentation of Irukandji Syndrome [2-8]?

• A mild sting (which can easily go unnoticed), a latent period of 10-45 minutes, then a rush of systemic symptoms
• Local erythema and piloerection may be seen in the shape of the bell or tentacles.
• Excruciating chest, back, and abdominal pain with significant muscle spasms
• Nausea, vomiting, and anxiety
• A sense of impending doom
• Severe hypertension is almost universally present initially
• Cardiogenic shock may follow initial hypertension and require pressor support
• Life-threatening sequelae include pulmonary edema, toxic cardiomyopathy, and intracranial hemorrhage, with fatalities reported

What is the treatment of Irukandji syndrome [2,6,9-11]?

• Vinegar (acetic acid) can be applied to envenomation site to inactivate nematocysts that have not yet fired. This is followed by careful removal of any retained tentacles.
• Pain management often requires large doses of opioids.
• Supportive care for nausea, vomiting, anxiety.
• Antihypertensives may be required; titratable agents such as esmolol are preferred as shock may develop later.
• About half of patients may require admission, with some requiring ICU level care.
• Intravenous magnesium salts have been proposed as an adjunct treatment for severe Irukandji syndrome but research to date is equivocal.

Clinical Pearls

• Initially thought to be confined to the Northern Australian coast, Irukandji syndrome has been reported throughout the tropics.
• The syndrome begins with mild sting and a latent period followed by severe systemic symptoms of excruciating pain and sequelae of a catecholamine surge.
• First aid includes dousing in the site with vinegar (acetic acid) for 30 seconds and removing any tentacles.
• Treatment is ABCs, then pain control with IV opioids along with antiemetics, anxiolytics, and antihypertensives.
• May require admission and possible ICU level care for life-threatening complications.