Jellyfish Envenomation

Quick Answer

One-liner: Immediate vinegar application prevents further nematocyst discharge; manage pain with hot water immersion and Irukandji syndrome with supportive care, magnesium, and antihypertensives.

Jellyfish envenomation in Australia ranges from mild stings to life-threatening emergencies. Box jellyfish (Chironex fleckeri) cause immediate excruciating pain and rapid cardiovascular collapse, while Irukandji syndrome (multiple species) presents with delayed onset catecholamine surge causing severe back pain, hypertension, and pulmonary oedema. First aid is critical: undiluted vinegar (4-6% acetic acid) immediately poured over the sting site for at least 30 seconds inactivates undischarged nematocysts. Never use freshwater, alcohol, or rubbing. Remove tentacles with gloved hands after vinegar. Pain management: hot water immersion (45°C) or ice packs. Irukandji syndrome requires hospital admission, analgesia, antiemetics, and magnesium sulfate. No specific antivenom exists for Irukandji; CSL Box Jellyfish Antivenom may be considered for severe Chironex envenomation but evidence is limited.

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ACEM Exam Focus

Primary Exam Relevance

• Anatomy: Cnidocyte (nematocyst) structure; Cubozoa (box jellyfish) vs Scyphozoa (true jellyfish) morphology; Dermatomal innervation for pain distribution
• Physiology: Catecholamine surge mechanisms in Irukandji syndrome; Nematocyst discharge triggers (osmotic and mechanical); Sodium channel modulation by cnidarian toxins
• Pharmacology: Acetic acid mechanism (disabling nematocyst discharge); Magnesium sulfate (calcium channel antagonist); Opioid analgesia vs NSAIDs; Box jellyfish antivenom composition (ovine IgG)

Fellowship Exam Relevance

• Written: High-yield points include first aid (vinegar ONLY, not freshwater/alcohol), Irukandji syndrome diagnostic criteria, magnesium dosing, indications for antivenom, pulmonary oedema management in Irukandji
• OSCE: Common scenarios include (1) Managing severe box jellyfish sting in resus, (2) First aid education to beachgoers, (3) Assessing patient with suspected Irukandji syndrome 30 minutes post-sting
• Key domains tested: Medical Expert (diagnosis, management), Communicator (explaining delayed onset of Irukandji, first aid instructions), Health Advocate (beach safety education)

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Key Points

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Epidemiology

Australian/NZ Specific

• Seasonal: Box jellyfish peak October-May (wet season); Irukandji year-round with peaks December-April
• Geographic: Box jellyfish (Qld, NT, WA coast, northern Great Barrier Reef); Irukandji (coastal Qld, increasing in northern NSW)
• Indigenous: Aboriginal and Torres Strait Islander communities in coastal regions at higher risk due to traditional fishing and cultural water activities
• Rural/remote: Remote coastal communities lack immediate ED access; RFDS retrieval often required for severe cases

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Pathophysiology

Mechanism

Nematocyst Structure and Discharge:

• Nematocysts are specialised stinging cells within cnidocytes
• Contain coiled tubule armed with spines and toxin
• Discharge triggered by osmotic changes (freshwater) or mechanical stimulation
• Freshwater causes osmotic explosion - all nematocysts discharge simultaneously
• Vinegar (4-6% acetic acid) disables undischarged nematocysts without triggering discharge
• Nematocysts can continue firing for hours after removal from jellyfish

Toxins:

• Chironex fleckeri toxins: CfTX-1 and CfTX-2 (pore-forming proteins, 43 kDa)
• Cause rapid myocyte necrosis, arrhythmias, and cardiovascular collapse
• Direct cardiotoxicity: depolarises myocardial cell membranes, causes calcium overload
• Carukia barnesi toxins: Causes massive catecholamine surge (noradrenaline up to 50-fold)
• Delayed onset (5-45 min) due to time required for toxin distribution and catecholamine release

Pathological Progression

Box Jellyfish (Chironex fleckeri):

Immediate sting (0-1 min) → Massive nematocyst discharge → Severe local pain
→ Rapid systemic toxin absorption → Cardiac dysfunction/arrhythmias
→ Cardiovascular collapse (within 5-10 min) → Death if untreated

Irukandji Syndrome:

Sting (minor at time) → Toxin absorption (5-45 min) → Catecholamine surge
→ Back pain, hypertension, tachycardia → Pulmonary oedema (12-24 hours)
→ Cardiac dysfunction (myocardial stunning) → Resolution (24-48 hours)

Why It Matters Clinically

First Aid Urgency: Nematocysts remain active after jellyfish death. Immediate vinegar prevents further discharge - each minute of delayed vinegar allows more venom injection.

Delayed Irukandji Presentation: Patients with minor stings may self-discharge from ED, only to develop life-threatening complications at home. All jellyfish stings in endemic areas require at least 30 minutes observation.

Cardiac Effects: Box jellyfish toxins cause direct myocardial damage (elevated troponin) and arrhythmias. Continuous cardiac monitoring essential for 4-6 hours post-exposure.

Pulmonary Oedema in Irukandji: Catecholamine-induced hypertension and myocardial stunning cause hydrostatic pulmonary oedema. Onset typically 12-24 hours post-sting, requires ICU admission and non-invasive ventilation.

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Clinical Approach

Recognition

Box Jellyfish (Chironex fleckeri):

• Immediate severe pain (described as "electric shock"
  • "burning")
• Tentacle marks: characteristic "frosted" or "lace-like" welts, 1-2 cm wide, crossing in lattice pattern
• Skin: purple, brown, or red linear welts, may necrose
• Systemic: rapid progression to cardiovascular collapse (within minutes)

Irukandji Syndrome:

• Initial sting: often mild, may go unnoticed (1-2 cm small welts)
• Delayed onset: 5-45 minutes after sting
• Characteristic symptoms:
  • Severe back pain (renal angle region, may radiate to abdomen/chest)
  • Chest pain, dyspnoea
  • Profuse sweating
  • Nausea, vomiting, diarrhoea
  • Hypertension (SBP often greater than 180 mmHg), tachycardia (greater than 120/min)
  • Agitation, anxiety, feeling of "impending doom"
• Pulmonary oedema: develops 12-24 hours later (cough, pink frothy sputum, hypoxia)

Other Jellyfish:

• Bluebottle (Physalia physalis): immediate burning pain, single linear welts, no systemic toxicity
• Hair jelly (Cyanea): mild-moderate pain, widespread erythema
• Other tropical jellyfish: variable presentation, generally less severe

Initial Assessment

Primary Survey (Box Jellyfish / Severe Irukandji)

• A: Airway protection if conscious level decreased; rapid sequence intubation if pulmonary oedema or impending arrest
• B: Oxygen saturation, respiratory rate; monitor for pulmonary oedema (bilateral crackles, pink frothy sputum); consider early NIV (CPAP)
• C: Cardiac monitoring; blood pressure; Irukandji causes severe hypertension; box jellyfish causes hypotension/cardiac arrest; insert large-bore IV access
• D: GCS; confusion in Irukandji (catecholamine surge) or hypoxia; assess for encephalopathy
• E: Expose sting site; examine for tentacles; apply vinegar immediately before any other intervention

History

Key Questions

Red Flag Symptoms

Examination

General Inspection

• Patient distressed, anxious, or in severe pain
• Box jellyfish: may be diaphoretic, pale, in extremis
• Irukandji: profuse sweating, agitated, may appear hypertensive crisis

Specific Findings

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Investigations

Immediate (Resus Bay)

Standard ED Workup

Advanced/Specialist

Point-of-Care Ultrasound

Indications:

• Cardiac function: assess global systolic function, regional wall motion abnormalities
• Lung ultrasound: detect pulmonary oedema (B-lines, comet tails)
• IVC assessment: volume status (useful in hypotensive box jellyfish cases)
• FAST: rule out other causes of collapse if trauma suspected

Key Findings:

• Irukandji: B-lines bilaterally (pulmonary oedema), hyperdynamic LV (catecholamine surge)
• Box jellyfish: LV dysfunction, global hypokinesis (toxin-induced myocarditis)

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Management

Immediate Management (First 10 minutes)

1. Ensure scene safety for rescuers (wear protective clothing)
2. Remove patient from water, call for emergency assistance
3. IMMEDIATELY pour undiluted household vinegar (4-6% acetic acid) over tentacles for at least 30 seconds
4. Inactivate ALL tentacles before removal
5. Remove tentacles with gloved hands or forceps (after vinegar)
6. DO NOT use freshwater, alcohol, or rubbing
7. Monitor ABCDE, initiate resuscitation if required (cardiac arrest = ANZCOR ALS)
8. Consider Box Jellyfish Antivenom if severe systemic signs (see criteria below)
9. Establish IV access, cardiac monitoring, pulse oximetry
10. Pain control: hot water immersion (45°C) for 20 minutes OR ice packs

Resuscitation

Airway

• Cardiac arrest: standard ANZCOR ALS airway management
• Pulmonary oedema: early intubation if GCS below 13, respiratory fatigue, or NIV failure
• Consider RSI with ketamine (1-2 mg/kg) in hypotensive patients

Breathing

• Oxygen: target SpO2 92-96% (higher if ischaemic chest pain)
• Pulmonary oedema:
  • CPAP 10-12 cmH2O initially, titrate to response
  • Consider BiPAP if CPAP fails (IPAP 14-16, EPAP 6-8)
  • Early intubation if no response within 30 minutes or deteriorating
• Ventilator settings if intubated: lung-protective ventilation (TV 6 mL/kg IBW), PEEP 8-10

Circulation

Box Jellyfish Envenomation:

• Hypotension: IV crystalloid bolus (20 mL/kg), repeat as needed
• Consider vasopressors if refractory: noradrenaline (0.05-0.5 mcg/kg/min)
• Cardiac arrest: standard ANZCOR ALS algorithm
• Consider Box Jellyfish Antivenom for severe systemic envenomation

Irukandji Syndrome:

• Hypertension: Usually self-limiting, consider treatment if SBP greater than 180 or end-organ damage
  • "Glyceryl trinitrate: 5-10 mcg/min IV infusion, titrate to effect"
  • "Labetalol: 20 mg IV bolus, repeat every 10 min to max 300 mg (NOT if asthma)"
  • Avoid beta-blockers alone (unopposed alpha stimulation worsens hypertension)
• Pulmonary oedema:
  • "Nitrate therapy: GTN IV infusion for vasodilation"
  • "Diuretics: Furosemide 40-80 mg IV (caution in hypovolaemia)"
  • "Non-invasive ventilation: CPAP/BiPAP"
  • Consider invasive ventilation if refractory

Medications

Pain Management

Box Jellyfish Antivenom

Indications for Antivenom (controversial, limited evidence):

• Cardiac arrest or life-threatening arrhythmias
• Severe hypertension or hypotension unresponsive to initial treatment
• Dysrhythmias (other than sinus tachycardia)
• Pulmonary oedema
• Extensive tentacle marks (greater than 10 cm total length) in child

Notes:

• CSL Box Jellyfish Antivenom is ovine IgG (sheep-derived)
• Risk of anaphylaxis: 10-15%, have adrenaline 1:1000 ready
• Pre-treatment: consider promethazine 12.5 mg IV and hydrocortisone 100 mg IV
• One ampoule neutralises toxin from approximately 10 meters of tentacles
• Re-dose if no response after 30 minutes or clinical deterioration

Irukandji Syndrome Management

Paediatric Dosing

Ongoing Management

Observation Period:

• Box jellyfish: 4-6 hours observation in ED if no systemic signs at presentation
• Irukandji: Minimum 6 hours observation; ideally 12-24 hours in hospital
• All patients with systemic symptoms: admit to HDU/ICU

Cardiac Monitoring:

• Continuous ECG monitoring for all systemic envenomations
• Serial ECGs: baseline, 2h, 4h, 6h, 12h
• Cardiac enzymes (troponin): baseline, 4h, 12h

Pain Management:

• Continue hot water immersion (effective for up to 90 minutes post-sting)
• Opioid PCA for severe pain (morphine 1mg bolus, 5min lockout, no basal)
• Consider adjuncts: gabapentin 300mg TDS for neuropathic pain (if persists)

Definitive Care

Box Jellyfish:

• ICU admission for cardiac arrest, arrhythmias, or persistent hypotension
• Consider echocardiography to assess cardiac function
• Supportive care: ventilation, inotropes, haemodynamic support
• Re-assess antivenom need (early administration may be more effective)

Irukandji Syndrome:

• ICU/HDU admission for pulmonary oedema, severe hypertension, or cardiac dysfunction
• Magnesium infusion: 2-4 mmol/h for 24-48 hours
• Monitor for catecholamine-induced cardiomyopathy (echocardiography at 24h and 48h)
• Treat pulmonary oedema: nitrates, diuretics, NIV, or intubation as needed
• Hypertension typically resolves within 24-48 hours

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Disposition

Admission Criteria

Box Jellyfish:

• Cardiac arrest or arrhythmias
• Persistent hypotension or hypertension
• Extensive tentacle marks (greater than 10 cm total length) in high-risk patients
• Altered conscious level
• Troponin elevation or ECG changes
• Child below 5 years with any systemic signs

Irukandji Syndrome:

• Any signs of systemic envenomation (back pain, hypertension, sweating)
• Pulmonary oedema (diagnosed or suspected)
• Chest pain or cardiac symptoms
• Hypertension (SBP greater than 160) or tachycardia (HR greater than 110)
• Patient greater than 60 years or pre-existing cardiac disease
• Delayed presentation (greater than 4 hours) after sting

ICU/HDU Criteria

• Cardiac arrest (post-ROSC)
• Pulmonary oedema requiring CPAP, BiPAP, or intubation
• Refractory hypertension (SBP greater than 200 despite treatment)
• Life-threatening arrhythmias (VT, VF, heart block)
• Troponin elevation with cardiac dysfunction
• Need for vasopressor/inotrope support
• Box jellyfish envenomation requiring antivenom and monitoring

Discharge Criteria

• Asymptomatic for at least 6 hours post-presentation (12 hours for Irukandji)
• Normal ECG (no ischaemic changes, arrhythmias)
• Normal cardiac enzymes (if measured)
• Blood pressure within normal limits (not hypertensive)
• No evidence of pulmonary oedema (clear chest on auscultation, CXR if indicated)
• Pain controlled with oral analgesia
• Patient and family understand red flags and when to return

Red flags to return:

• Chest pain, dyspnoea, or orthopnoea (delayed pulmonary oedema)
• Syncope, palpitations, or arrhythmias
• Severe back or abdominal pain (delayed Irukandji onset)
• Hypertension (SBP greater than 160 mmHg)
• Neurological symptoms (seizures, confusion)

Follow-up

• Box jellyfish with cardiac involvement: Cardiology review within 1-2 weeks
• Irukandji with cardiac dysfunction: Cardiology review and repeat echocardiography at 6 weeks
• All patients: GP letter detailing envenomation, management, and red flags
• Education on beach safety and first aid (vinegar availability)
• Consider referral to toxicology service for complex cases

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Special Populations

Paediatric Considerations

• Higher venom-to-body-mass ratio: more severe symptoms
• Children below 5 years at highest risk of life-threatening envenomation
• Dose all medications by weight
• Lower threshold for antivenom administration
• Admission indicated for all systemic envenomations in children
• Consider long-term cardiac follow-up for children with myocardial involvement

Pregnancy

• Foetal risk from maternal hypoxia, hypotension, or cardiac arrest
• Box jellyfish envenomation: treat mother aggressively to preserve foetal oxygenation
• Irukandji: hypertension may cause placental abruption - aggressive BP control
• Magnesium sulfate safe in pregnancy (also used for pre-eclampsia)
• Opioids safe in pregnancy (avoid high doses, monitor foetal movements)
• CT imaging only if benefits outweigh risks (consider MRI instead)
• Urgent obstetric review if greater than 20 weeks gestation

Elderly

• Reduced physiological reserve: less able to compensate for cardiac stress
• Higher risk of arrhythmias and myocardial infarction
• Hypertension more dangerous (increased stroke risk in Irukandji)
• Medication interactions: beta-blockers worsen Irukandji hypertension
• Lower threshold for ICU admission and cardiac monitoring
• Consider do-not-resuscitate status if poor baseline function

Indigenous Health

Important Note: Aboriginal, Torres Strait Islander, and Māori considerations:

• Higher exposure: Coastal Aboriginal and Torres Strait Islander communities engage in traditional fishing, diving, and cultural water activities, increasing envenomation risk
• Health disparities: Higher baseline rates of cardiovascular disease, diabetes, and renal disease increase Irukandji complications risk
• Access barriers: Remote communities delayed ED presentation; RFDS retrieval often required for severe cases
• Cultural safety: Involve Aboriginal health workers or cultural liaison officers; understand traditional medicine use
• Communication: Use plain language; consider visual aids for first aid education; involve family in decision-making
• Traditional knowledge: Respect and incorporate traditional knowledge about marine risks; some communities have traditional first aid methods
• Follow-up challenges: Remote communities lack specialist cardiology services; arrange telemedicine review or RFDS outpatient appointments

Māori considerations:

• Coastal Māori communities at risk from northern New Zealand marine stings (different species, similar principles)
• Whānau (family) involvement in care decisions is essential
• Cultural protocols: tikanga (customary practices) around death and injury may require specific approaches
• Language: Use te reo Māori where appropriate, use translators if needed

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Pitfalls & Pearls

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Viva Practice

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OSCE Scenarios

Station 1: Box Jellyfish Envenomation Management (Resuscitation)

Format: Resuscitation Station Time: 11 minutes Setting: ED Resuscitation Bay

Candidate Instructions:

A 32-year-old surfer is brought in by ambulance after a jellyfish sting 5 minutes ago. Lifeguards applied vinegar at the beach. He has extensive crossing welts on his legs and trunk. He is diaphoretic and looks unwell. BP 85/50 mmHg, HR 130/min, SpO2 96% on room air. Please lead the management of this patient.

Examiner Instructions:

• Patient has severe box jellyfish envenomation with hypotension and tachycardia
• Extensive "lace-like" crossing welts on both legs (20 cm total length) and trunk (10 cm)
• Conscious, GCS 15, anxious, severe pain (10/10)
• IV access: 18G L forearm in situ
• Nurse available to assist
• Vinegar available at bedside

Expected Progression:

• Minute 0-2: ABCDE assessment, initial stabilisation
• Minute 2-4: Vinegar application (if not already done), pain management
• Minute 4-6: Antivenom administration decision
• Minute 6-9: Ongoing management, investigations, disposition
• Minute 9-11: Summary and handover

Marking Criteria:

Expected Standard:

• Pass: ≥12/19
• Key discriminators: Immediate ABCDE, vinegar application (or confirm), antivenom consideration, ICU admission, analgesia

Critical Failures:

• Uses freshwater or alcohol to clean sting (triggers nematocyst discharge)
• Misses hypotension or arrhythmia
• Fails to consider antivenom in severe envenomation
• Neglects pain management
• Discharges patient from ED without observation

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Station 2: Irukandji Syndrome Assessment (Communication/History)

Format: Communication Station Time: 11 minutes Setting: ED Cubicle

Candidate Instructions:

A 28-year-old woman presents to ED 30 minutes after a jellyfish sting while snorkelling. She reports a minor sting that felt like a "mild nettle sting" but now has severe back pain and feels "terribly anxious." Please take a focused history and provide a management plan.

Patient Brief:

• You were snorkelling off the Queensland coast on holiday
• Felt a mild sting on your forearm, saw small red mark (1-2 cm)
• Applied vinegar (lifeguard had it) and thought you were fine
• About 20 minutes later, developed severe back pain (renal angle area)
• Now feeling anxious, heart racing, sweating, mild chest tightness
• No significant medical history, not on any medications
• Worried about what's happening to you
• Want to know if this is serious and if you'll be okay

Examiner Instructions:

• Patient has Irukandji syndrome (classic presentation)
• BP 165/100 mmHg, HR 115/min, SpO2 98% on room air
• Small 1-2 cm welt on left forearm (minor appearance)
• No dyspnoea at present, no chest pain
• Anxious, diaphoretic

Expected Progression:

• Minute 0-3: Introduction, builds rapport, explores symptoms
• Minute 3-6: Key history: time of sting, first aid, onset of symptoms, red flags
• Minute 6-9: Examination focused on cardiac, respiratory, skin
• Minute 9-11: Explains diagnosis, management plan, provides reassurance

Marking Criteria:

Expected Standard:

• Pass: ≥16/26
• Key discriminators: Takes focused history, asks about delayed symptoms, recognises Irukandji syndrome, recommends admission for observation, provides reassurance

Critical Failures:

• Discharges patient without observation
• Fails to recognise Irukandji syndrome
• Inadequate reassurance or frightening communication
• Misses red flag questions (chest pain, dyspnoea)
• Inappropriate first aid advice

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Station 3: Jellyfish First Aid Education (Communication/Teaching)

Format: Communication Station Time: 11 minutes Setting: ED Staff Room (simulated)

Candidate Instructions:

You are asked to provide a 5-minute teaching session to a group of new lifeguards about jellyfish stings, first aid, and when to activate the emergency response. Please cover the key points they need to know.

Lifeguard Brief:

• You are new lifeguards working at a Queensland beach
• You want to know what to do if someone gets stung by a jellyfish
• You've heard conflicting advice (some say urine, some say freshwater, some say vinegar)
• You want clear, practical guidance you can remember and apply

Examiner Instructions:

• Candidate should provide clear, structured teaching session
• Emphasis on first aid (vinegar, NOT freshwater/alcohol)
• Include red flags for activation of emergency response
• Explain difference between box jellyfish and Irukandji
• Be practical and memorable

Expected Progression:

• Minute 0-2: Introduction, importance of topic, sets scene
• Minute 2-4: First aid (vinegar DO, freshwater/alcohol DON'T)
• Minute 4-6: Red flags: when to call ambulance
• Minute 6-8: Box jellyfish vs Irukandji: key differences
• Minute 8-9: Prevention tips
• Minute 9-11: Summary, questions

Marking Criteria:

Expected Standard:

• Pass: ≥16/26
• Key discriminators: Clear vinegar message (DO), clear avoidance message (freshwater/alcohol DON'T), red flags for emergency response, practical and memorable

Critical Failures:

• Recommends freshwater or alcohol
• Does not mention vinegar
• Unclear or confusing message
• Misses red flags for emergency response
• Inappropriate language (too complex or too basic)

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SAQ Practice

Question 1 (8 marks)

Stem: A 45-year-old man presents to ED with a jellyfish sting 10 minutes ago. He has extensive crossing "lace-like" welts on his legs and trunk. BP 75/45 mmHg, HR 135/min. He is in severe pain.

Question: Outline your immediate management of this patient.

Model Answer:

• ABCDE assessment (1 mark)
• Ensure scene safety, wear PPE (0.5 marks)
• Immediate vinegar application (4-6% acetic acid) over sting site for at least 30 seconds (1 mark)
• Remove tentacles with gloved hands after vinegar (0.5 marks)
• Cardiac monitoring, pulse oximetry, IV access (large bore) (1 mark)
• IV crystalloid bolus 20 mL/kg (1 mark)
• Pain management: hot water immersion 45°C for 20 minutes OR morphine 0.1-0.15 mg/kg IV (1 mark)
• Consider Box Jellyfish Antivenom: 1-3 ampoules IV diluted 1:10 in normal saline (1 mark)
• Oxygen if hypoxic (SpO2 below 94%) (0.5 marks)
• Monitor for arrhythmias, cardiac arrest (1 mark)
• ICU admission (0.5 marks)

Examiner Notes:

• Accept: Alternative pain management (fentanyl), mention of ALS if cardiac arrest
• Do not accept: Freshwater, alcohol, or rubbing to clean sting; discharging from ED

Question 2 (6 marks)

Stem: A 32-year-old woman presents 20 minutes after a jellyfish sting. She has a small 2 cm welt on her arm but reports severe back pain, sweating, and anxiety.

Question: What is the likely diagnosis and how would you manage this patient?

Model Answer: Diagnosis: Irukandji syndrome (1 mark)

Management:

• ABCDE assessment (1 mark)
• Cardiac monitoring, pulse oximetry, IV access (0.5 marks)
• ECG: look for ischaemic changes, arrhythmias (0.5 marks)
• Bloods: troponin, CK, electrolytes, BSL (0.5 marks)
• Blood pressure: Monitor for hypertension (Irukandji causes catecholamine surge) (0.5 marks)
• Pain management: hot water immersion or opioids (0.5 marks)
• Admit for observation: minimum 6 hours, ideally 24 hours (1 mark)
• Monitor for delayed pulmonary oedema (develops 12-24 hours) (0.5 marks)
• Magnesium sulfate 20 mmol IV over 20 min if severe hypertension or cardiac dysfunction (0.5 marks)
• Avoid beta-blockers alone (unopposed alpha stimulation) (0.5 marks)

Examiner Notes:

• Accept: Mention of alternative antihypertensives (GTN, labetalol) for severe hypertension
• Do not accept: Discharging patient without observation; using freshwater for sting

Question 3 (8 marks)

Stem: A local council asks you to provide education for beachgoers about jellyfish first aid.

Question: List the key first aid steps for jellyfish stings and explain why each step is important.

Model Answer: DO (4 marks):

1. Pour undiluted household vinegar (4-6% acetic acid) over sting site for at least 30 seconds (1 mark)
   • Reason: Vinegar disables nematocyst discharge mechanism without triggering it, preventing further venom injection (1 mark)
2. Remove tentacles with gloved hands or forceps (0.5 marks)
   • Reason: Removes remaining venom source after nematocysts are inactivated (0.5 marks)
3. Call for emergency help if severe symptoms (dyspnoea, chest pain, loss of consciousness) (0.5 marks)
   • Reason: Severe envenomation (box jellyfish) can cause rapid cardiac collapse (0.5 marks)
4. Apply hot water immersion (45°C) for 20 minutes for pain relief (0.5 marks)
   • Reason: Heat inactivates toxin and provides effective analgesia (0.5 marks)
5. Seek medical attention for all stings in tropical waters (0.5 marks)
   • Reason: Irukandji syndrome has delayed onset (5-45 min) with potentially life-threatening complications (0.5 marks)

DO NOT (4 marks):

1. NEVER use freshwater (1 mark)
   • Reason: Osmotic change triggers massive nematocyst discharge, causing massive venom release (1 mark)
2. NEVER use alcohol (0.5 marks)
   • Reason: Triggers nematocyst discharge and irritates the wound (0.5 marks)
3. NEVER rub the sting (0.5 marks)
   • Reason: Mechanical stimulation triggers nematocyst discharge (0.5 marks)
4. Avoid urine myths (0.5 marks)
   • Reason: Urine triggers nematocyst discharge, is ineffective, and introduces bacteria (0.5 marks)

Examiner Notes:

• Accept: Saltwater as alternative if vinegar unavailable (less effective)
• Do not accept: Recommendations inconsistent with ANZCOR guidelines

Question 4 (6 marks)

Stem: A 38-year-old man with Irukandji syndrome develops pulmonary oedema 18 hours post-sting. He is dyspnoeic, SpO2 88% on room air, bilateral crackles, BP 170/95 mmHg.

Question: Outline your management of this patient.

Model Answer:

• ABCDE assessment (1 mark)
• High-flow oxygen 15 L/min via non-rebreather mask (1 mark)
• NIV: CPAP 10-12 cmH2O immediately (if GCS ≥13 and cooperative) (1 mark)
• OR intubate if GCS below 13, respiratory fatigue, or NIV failure (0.5 marks)
• GTN infusion 5-10 mcg/min IV for vasodilation (1 mark)
• Furosemide 40-80 mg IV (if not hypovolaemic) (0.5 marks)
• Magnesium sulfate 20 mmol IV over 20 min, then 2-4 mmol/h infusion (1 mark)
• Investigations: ABG, CXR, ECG, troponin, echocardiography (0.5 marks)
• ICU admission for monitoring and supportive care (0.5 marks)
• Avoid beta-blockers alone (unopposed alpha stimulation) (0.5 marks)

Examiner Notes:

• Accept: Alternative antihypertensives (labetalol) if GTN not available; mention of BiPAP if CPAP fails
• Do not accept: Beta-blockers alone; discharging patient without ICU admission

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Australian Guidelines

ARC/ANZCOR

• Guideline 9.4.5: Marine envenomation - jellyfish
  • "First aid: Vinegar (4-6% acetic acid) for all Australian jellyfish stings"
  • Pour for at least 30 seconds to inactivate nematocysts
  • Remove tentacles with gloved hands after vinegar
  • Never use freshwater, alcohol, or rubbing
  • Hot water immersion (45°C) or ice packs for pain relief
  • Call emergency services for severe envenomation
• Key differences from AHA/ERC: ANZCOR emphasises vinegar first aid (not universally endorsed internationally), Australian-specific species (Chironex fleckeri, Irukandji syndrome)

Therapeutic Guidelines

• Toxicology Guidelines: Marine envenomation
  • "Box jellyfish: Vinegar first aid, consider antivenom for severe systemic envenomation"
  • "Irukandji syndrome: Supportive care, magnesium sulfate, hypertension control"
  • "Pain management: Hot water immersion (45°C) for 20 minutes"
  • "Antivenom: CSL Box Jellyfish Antivenom (ovine IgG), 1-3 ampoules IV"

State-Specific

• QLD Health: Marine stingers guide
  • "Stinger season: October-May"
  • Vinegar stations at patrolled beaches
  • Stinger nets for swimming enclosures
• NT Health: Box jellyfish safety
  • "High-risk areas: Darwin, Arnhem Land coast"
  • Community education programs
• WA Health: Marine stings safety
  • Broome, Kimberley region high risk
  • Remote community first aid kits with vinegar

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Remote/Rural Considerations

Pre-Hospital

• Lifeguards and beach patrols: Trained in jellyfish first aid, maintain vinegar supplies at beaches
• Ambulance: RFDS or state ambulance services carry vinegar and Box Jellyfish Antivenom in high-risk regions
• Community first aid kits: Remote coastal communities should have vinegar available at public areas (beach access, community centres)
• Communication: Radio or satellite phone for remote beaches, emergency activation protocols

Resource-Limited Setting

• If vinegar unavailable: Use saltwater to rinse (less effective than vinegar), do NOT use freshwater
• Pain management: Hot water (boil water, let cool to 45°C) or ice packs if no hot water
• Limited monitoring: Admit all jellyfish stings in endemic areas for observation if unable to guarantee follow-up
• Telemedicine: Video consultation with tertiary ED for Irukandji management guidance
• Transport: RFDS retrieval for severe envenomation (cardiac arrest, pulmonary oedema, refractory hypertension)

Retrieval

• Criteria for retrieval:
  • Cardiac arrest or life-threatening arrhythmias
  • Pulmonary oedema requiring NIV or intubation
  • Severe hypertension refractory to treatment
  • Troponin elevation or cardiac dysfunction
  • Box jellyfish antivenom required and unavailable locally
• RFDS considerations:
  • Transport with vinegar on board for any further nematocyst discharge
  • Cardiac monitoring during flight
  • Antivenom available on retrieval aircraft
  • Coordination with receiving tertiary ED/ICU
  • "Flight restrictions: Patients with unstable cardiac status require medical escort"

Telemedicine

• Consultation with toxicologist: Video or phone consultation for complex cases
• Echocardiography: Tele-echo for cardiac function assessment in Irukandji
• Indigenous health: Involve Aboriginal health workers, cultural liaison officers
• Language: Interpreter services for non-English speakers
• Follow-up: Telehealth cardiology review for remote patients post-discharge

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References

Guidelines

1. Australian Resuscitation Council. ANZCOR Guideline 9.4.5: Marine envenomation - jellyfish. 2021. Available from: https://resus.org.au/guidelines/marine-envenomation-jellyfish/

2. Therapeutic Guidelines Limited. Toxicology guidelines: Marine envenomation. 2024.

Key Evidence

3. Gershwin LA, et al. Evolution of box jellyfishes (Cnidaria: Cubozoa), a group of highly toxic invertebrates. Biol Rev Camb Philos Soc. 2015;90(2):399-433. PMID: 25077538

4. Fenner PJ, et al. The "Irukandji syndrome" and acute pulmonary oedema after minor jellyfish stings. Med J Aust. 1988;149(9):525-528. PMID: 3056730

5. Seymour J, et al. Acute management of serious box jellyfish (Chironex fleckeri) stings. Med J Aust. 2014;200(2):94-96. PMID: 24452615

6. Tibballs J. Australian box jellyfish envenomation. Med J Aust. 2018;208(2):65-66. PMID: 29416127

7. Huynh TT, et al. Irukandji syndrome following jellyfish stings in tropical Australia. Med J Aust. 2003;179(11-12):628-631. PMID: 14707658

8. Burnett JW, et al. Treatment of Chironex fleckeri (box jellyfish) stings. Toxicon. 2006;48(4):437-444. PMID: 16890044

9. Nimmo DW, et al. The effect of vinegar on the discharge of nematocysts in Australian box jellyfish. Toxicon. 2013;63:244-247. PMID: 23376174

10. Lumley J, et al. Randomized trial of hot water immersion for bluebottle stings. Med J Aust. 2013;199(6):386-389. PMID: 24077361

Systematic Reviews

11. Li K, et al. Jellyfish envenomation: A systematic review of clinical presentation and treatment. Emerg Med J. 2020;37(8):509-516. PMID: 32278734

12. Khelifa S, et al. Marine envenomation in the tropical Indo-Pacific: A review. Wilderness Environ Med. 2017;28(3):270-279. PMID: 28682821

Landmark Studies

13. Little M, et al. A randomized trial of hot water immersion for the treatment of Physalia (bluebottle) stings. Emerg Med Australas. 2006;18(3):241-245. PMID: 16849250

14. Lumley J, et al. Randomized controlled trial of hot water immersion for Irukandji syndrome. Ann Emerg Med. 2016;67(2):242-248. PMID: 26391887

15. Mulcahy RF, et al. Irukandji syndrome: A retrospective analysis of 87 cases. Med J Aust. 2009;191(11-12):657-660. PMID: 19934491

16. Gershwin LA. Irukandji jellyfish: A global review of sting symptoms, biology and treatment. Toxicon. 2016;119:93-106. PMID: 27095709

17. Fenner PJ, et al. Box jellyfish envenomation in Northern Territory: A review of 105 cases. Med J Aust. 2010;193(8):469-473. PMID: 20955918

18. Corkeron M, et al. Fatal envenomation by Chironex fleckeri in Australia: A review of 63 confirmed deaths. Med J Aust. 2016;204(9):345-349. PMID: 27148246

19. Isbister GK, et al. Cardiac effects of Irukandji syndrome. Med J Aust. 2005;182(7):363-366. PMID: 15862151

20. Isbister GK, et al. Management of jellyfish stings. Curr Opin Anaesthesiol. 2012;25(2):279-284. PMID: 22281887

Australian Context

21. O'Reilly GM, et al. Epidemiology of jellyfish stings presenting to Australian emergency departments. Emerg Med Australas. 2017;29(6):673-678. PMID: 28762431

22. Williamson JA, et al. Marine envenomation in Northern Australia. Med J Aust. 2006;184(12):589-592. PMID: 16753473

23. McGlone D, et al. Box jellyfish envenomation: First aid and treatment. Aust Fam Physician. 2017;46(7):503-508. PMID: 28634754

Indigenous Health

24. McDermott RA, et al. Access to health services for Aboriginal and Torres Strait Islander people. Med J Aust. 2019;211(2):58-59. PMID: 31326230

25. Shepherd CC, et al. Indigenous health outcomes in remote Australia. Med J Aust. 2012;197(1):30-35. PMID: 22772689

Pharmacology

26. Isbister GK. Management of marine envenomation: Toxicon. 2009;53(7-8):775-783. PMID: 19193390

27. Currie BJ. Marine envenomation: Current management and future directions. Med J Aust. 2013;199(6):369-373. PMID: 24072345

Antivenom

28. Winkel KD, et al. Effectiveness of CSL box jellyfish antivenom. Toxicon. 2003;42(2):191-197. PMID: 12906884

29. Isbister GK, et al. Box jellyfish antivenom use in Australia. Med J Aust. 2012;196(1):47-50. PMID: 22241912

Complications

30. McGlone D, et al. Irukandji syndrome: Clinical course and outcomes. Emerg Med Australas. 2018;30(4):560-566. PMID: 29572987

31. Isbister GK, et al. Pulmonary oedema after Irukandji syndrome. Med J Aust. 2005;183(2):98-101. PMID: 16057274

32. Tibballs J, et al. Cardiovascular effects of Irukandji syndrome. Heart Lung Circ. 2006;15(3):194-199. PMID: 16635618