Irukandji Jellyfish

Irukandji Syndrome – originally a mystery was solved by some self experimentation of Dr Jack Barnes, his nine-year old son and local surf lifesaver. He proved that the thumbnail sized carybdeid (or four tentacled box jellyfish) could cause Irukandji syndrome but placing it on all three of them. A subsequent hospital admission was required for all three as severe abdominal pain and vomiting ensued. (For the full story follow this link).

Irukandji syndrome occurs once the person has left the tropical waters of either Australia, Hawaii, Caribbean, South East Asia or Papua New Guinea. It is characterised by dysphoria, severe generalised pain, sweating, hypertension and rarely pulmonary oedema. This is all with the absence of any dermal findings. 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.

Resus

Potential life threats include:

• Pulmonary oedema
• Severe hypertension, if refractory to opiate analgesia given an IV infusion of glyceryl trinitrate (50mg in 100 ml starting at 6 ml/minute; 1-4 microgram/kg/minute in children). Titrate to achieve a systolic blood pressure < 160 systolic

Risk Assessment

Typical symptoms include:

• Sting usually once leaving the water followed by systemic symptoms 30 to 120 minutes later. Usually there are no dermal signs
• Systemic features include a sense of impending doom, agitation, dysphoria, vomiting, sweating and severe pain in the back, limbs, abdomen. Hypertension and tachycardia are common. These symptoms usually settle within 12 hours
• Severe envenoming usually occurs within 4 hours and will require significant opiate requirements. These patients are at risk of developing cardiomyopathy, cariogenic shock and pulmonary oedema which may require intubation and ventilation
• Intracerebral haemorrhage has been noted in two patients, although they were on warfarin it is possible that uncontrolled hypertension precipitated their bleeds

Supportive Care

• 1. Analgesia Typically they will require IV fentanyl (0.5-1 microgram/kg) every 10 minutes until analgesia is achieved, this maybe in the realms of 300 micrograms. Fentanyl is thought to be the opioid analgesic of choice due to the potential additional effect mediated by sodium channel antagonism. Morphine can also be used in equivocal doses
• Vinegar Has been effective for controlling pain and stopping any further discharge from any remaining nematocysts – these should then be removed with a hard piece of plastic e.g credit card or sticky tape
• Do not apply a dressing as this can cause firing the nematocysts and promote systemic envenomation
• Blood pressure can be controlled with GTN as described in the resuscitation section
• Patients in cariogenic shock or refractory hypotension may require inotropic support. For pulmonary oedema non-invasive ventilation maybe used alongside a GTN infusion. It maybe necessary to intubate and ventilate if the patient is in severe cardiogenic shock and these measures are not working

Investigations

• 12 lead ECG for evidence of any ischaemia
• Laboratory investigations should selected in the context of trying to rule out other differentials. However, if the patient is haemodynamically unstable check FBC, EUC, magnesium, calcium, phosphate, CK and troponin every 8 hours
• Chest X-ray for signs of pulmonary oedema
• Echocardiography would be useful for those patients requiring inotropes and with pulmonary oedema or hypotension

Differential Diagnosis:

• Bluebottle stings also have immediate pain but the pain usually resolves within 1-2 hours, systemic features are rare and dermal markings are present
• Envenoming by the box jellyfish is associated with immediate pain but dermal markings are characteristic in these cases
• In a diver decompression illness can lead to severe pain and collapse skin markings will also be absent

Antivenom

• None available

Disposition

• Patients without evidence of envenomation at two hours can be discharged
• Patients who have received IV opiates will need 6 hours observation to observe for clinical resolution of symptoms
• Anyone who is symptomatic will need an admission until symptoms resolve. Patients with haemodynamic instability or pulmonary oedema will need HDU/ICU level of care

Controversies

• IV magnesium has been advocated for analgesia but there is no published evidence to support its use
• The best agent to control hypertension and tachycardia is yet to be decided
• Benzodiazepines may have some role to help reverse some of the effects of catecholamine release
• Recent laboratory work shows that already discharged nematocysts may release more venom with the application of vinegar. Therefore future first aid recommendations may change.

References and Additional Resources:

Additional Resources:

• Chris Nickson – Spiders and Stingers – SMACC podcast
• Mark Little – Dangers of the deep – SMACC podcast.
• The Jack Barnes and the irukandji Enigma – history of irukandji
• Tox Conundrum 008 – Irukandji case 1
• Tox Conundrum 009 – Irukandji case 2

References:

• Armstrong J, Pascu O. Irukandji Syndrome, Toxicology Handbook Australia 4e, Elsevier 2022; 501-503
• Barnes JH. Cause and effect in Irukandji stingings, Medical Journal of Australia 1964; 1:897-904
• Huynh TT, Seymour J, Pereira P et al. Severity of Irukandji syndrome and nematocyst identification from skin scrapping. Medical Journal of Australia 2003; 178:38-41
• Little M, Mulcahy RF. A year’s experience of ‘Irukandji’ jellyfish envenomation in far north Queensland. Medical Journal of Australia 1998; 169:638-641
• Little M, Pereira P, Carrette T et al. Jellyfish responsible for Irukandji syndrome. Quarterly Journal of Medicine 2006; 99:425-427
• Macrocanis CJ, Hall NJ, Mein JK. Irukandji syndrome in northern Western Australia: an emerging health problem. Medical Journal of Australia 2004; 181(11/12): 699-702
• McCullagh N, Pereira P, Cullen P et al. Randomised trial of magnesium in the treatment of Irukandji syndrome. Emergency Medicine Australasia 2012; 24(5):560-565
• Dickson CP, Waugh EB, Jacups SP et al. Irukandji syndrome case series from Australia’s tropical Northern Territory. Annals of Emergency Medicine 2009; 54(3):395-403