Wilderness Medicine · Supplementary · from Wilderness Medicine

Case 3: Marine Envenomation (Box Jellyfish)

Patient Presentation

Demographics: 19-year-old male university student on spring break

Chief Complaint: "Something stung me in the water — my chest is tight and I can't breathe."

History of Present Illness: Mr. A.T. was swimming at a beach in northern Queensland, Australia at approximately 1400 hours when he felt immediate, excruciating pain across his right arm, right lateral chest, and right abdomen. He screamed and ran out of the water. Bystanders noted long, linear, erythematous, tentacle-pattern marks across the affected areas. Within 2-3 minutes, he developed severe chest tightness, dyspnea, nausea, and profuse diaphoresis. He became pale and felt like he was "going to die."

Lifeguards responded within 4 minutes and identified the injury as a probable major box jellyfish (Chironex fleckeri) sting based on the tentacle pattern, season (November — wet season/stinger season), and geographic location. They immediately doused the sting areas with household vinegar for 30 seconds, removed adherent tentacles using gloved hands, and called for ambulance paramedics. An EpiPen was administered by one lifeguard who suspected anaphylaxis, though the presentation was subsequently assessed as direct envenomation rather than allergic reaction.

En route to hospital (25-minute transport), the patient developed progressive hypotension, became obtunded, and developed a broad-complex tachycardia on the cardiac monitor. IV access was established and a 500 mL NS bolus administered. Box jellyfish antivenom was not available pre-hospital.

Past Medical History:

• No significant medical history
• No prior jellyfish stings
• No known allergies

Medications:

• None

Social History:

• University student studying marine biology (ironic context)
• Non-smoker
• Social alcohol (2-3 beers consumed earlier that day)
• Visiting from Melbourne (not familiar with local stinger dangers)
• No stinger suit worn despite posted warnings at beach

Family History:

• Non-contributory

Physical Examination

• Vital Signs (arrival to ED): BP 78/52 mmHg, HR 138 bpm (irregular, wide-complex), RR 28, SpO2 88% on 15L NRB mask, Temp 36.0°C, GCS 10 (E2V3M5)
• General: Obtunded, diaphoretic, marked pallor, in severe distress
• Skin/Envenomation:
• Linear, whip-like, erythematous-to-violaceous "frosted ladder" pattern tentacle marks across right forearm extending to right lateral chest wall and right upper abdomen
• Estimated sting surface area: ~20% of one arm plus ~10% of trunk = significant contact area (>4-5 meters of tentacle contact estimated)
• Cross-hatched "frosted" appearance typical of C. fleckeri nematocyst discharge pattern
• Surrounding skin edematous with early vesiculation
• No urticaria or angioedema (not anaphylaxis)
• Cardiovascular: Tachycardic, irregular; wide-complex rhythm on monitor (ventricular tachycardia); weak peripheral pulses; mottled extremities; capillary refill 5 seconds
• Pulmonary: Tachypneic; bilateral diffuse crackles; accessory muscle use; no wheeze (argues against anaphylaxis)
• Neurological: GCS 10; pupils 5 mm bilateral, reactive; no focal deficits; generalized agitation alternating with obtundation
• Abdomen: Guarding over right upper quadrant and flank at sting site; tender along tentacle tracks

Workup and Results

Laboratory Studies:

Imaging/Additional Studies:

• ECG: Wide-complex tachycardia (ventricular tachycardia) at 138 bpm; ST elevation in V1-V3 with reciprocal ST depression in lateral leads; peaked T-waves consistent with hyperkalemia
• Chest X-ray: Bilateral diffuse pulmonary edema (non-cardiogenic — venom-induced capillary leak)
• Point-of-care echocardiogram: Severely reduced LV function, estimated EF 25-30%; global hypokinesis; no pericardial effusion; IVC dilated with minimal respiratory variation
• Repeat ECG (post-treatment, 2 hours): Sinus tachycardia 110 bpm, narrow complex; ST changes resolving; QTc 490 ms

Clinical Image

Illustration showing the box jellyfish (Chironex fleckeri) tentacle nematocyst discharge mechanism, characteristic "frosted ladder" sting pattern on skin, and the cardiotoxic venom pathways leading to myocardial depression and cardiovascular collapse. Source: Educational illustration.

Diagnosis

Severe Chironex fleckeri (Box Jellyfish) Envenomation with Cardiovascular Collapse, Venom-Induced Cardiomyopathy, Hyperkalemia, and Non-Cardiogenic Pulmonary Edema

Key Diagnostic Criteria:

• Geographic and seasonal context: northern Queensland, Australia during wet/stinger season (October-May)
• Characteristic C. fleckeri sting pattern: linear "frosted ladder" tentacle marks with cross-hatched nematocyst pattern
• Extensive sting surface area (estimated >4-5 m tentacle contact — major envenomation)
• Cardiovascular collapse with cardiogenic shock (EF 25-30%, wide-complex tachycardia)
• Massively elevated troponin and CK-MB indicating severe myocardial injury
• Hyperkalemia (6.8 mEq/L) — venom-induced cell lysis and direct cardiac membrane toxicity
• Metabolic acidosis with elevated lactate — shock physiology

Treatment Plan

1. Immediate resuscitation (ED):

• Airway: RSI and intubation (GCS 10, pulmonary edema, impending respiratory failure); ketamine preferred induction agent (hemodynamic stability)
• Breathing: Mechanical ventilation with PEEP 10 cmH2O for pulmonary edema
• Circulation: IV crystalloid boluses (cautious in cardiogenic shock); vasopressor initiation: norepinephrine 0.1 mcg/kg/min titrated to MAP >65 mmHg

1. Box jellyfish antivenom (CSL Chironex fleckeri antivenom):

• 3 vials (60,000 units) IV diluted in 100 mL NS, infused over 15 minutes
• Repeat with additional 3 vials if no clinical improvement at 30 minutes (up to 6 vials total for severe envenomation)
• Monitor for anaphylaxis to antivenom (have epinephrine ready)

1. Hyperkalemia management (emergent):

• Calcium gluconate 10% — 30 mL IV over 5 minutes (cardiac membrane stabilization)
• Insulin 10 units IV + dextrose 50% 50 mL (intracellular potassium shift)
• Sodium bicarbonate 50 mEq IV (treats acidosis and shifts potassium)
• Continuous cardiac monitoring; repeat potassium at 30 and 60 minutes

1. Cardiovascular support:

• Dobutamine 5-10 mcg/kg/min for inotropic support (EF 25-30%)
• Magnesium sulfate 2 g IV (hypomagnesemia correction + antiarrhythmic)
• Amiodarone 150 mg IV if VT recurs (avoid in torsades; use Mg first)
• Serial echocardiography every 6-12 hours

1. Local wound management:

• Vinegar (4-6% acetic acid) was appropriately applied in field (inactivates undischarged nematocysts — specific to C. fleckeri)
• Do NOT apply fresh water, ice, or pressure bandage (can trigger nematocyst discharge)
• Gentle removal of remaining tentacle fragments with forceps
• Wound care: clean with saline, apply non-adherent dressings; monitor for necrosis

1. ICU management:

• Continuous invasive hemodynamic monitoring (arterial line, central venous catheter)
• Correct metabolic acidosis, hypocalcemia, hypomagnesemia
• DIC monitoring: serial coagulation studies, fibrinogen, platelet count
• Rhabdomyolysis protocol: aggressive IV fluids, maintain UOP >1 mL/kg/hr
• Pain management: IV morphine titrated (severe pain from sting sites)

1. Follow-up: ICU stay anticipated 3-7 days; echocardiography before discharge to document LV recovery (venom-induced cardiomyopathy is usually reversible); dermatology follow-up for sting site scarring; psychological support for acute traumatic event

Key Learning Points

• Chironex fleckeri (Australian box jellyfish) is the most venomous marine animal and one of the most venomous creatures on Earth; deaths can occur within 2-5 minutes of severe envenomation, primarily from cardiovascular collapse due to direct cardiotoxic venom effects
• The venom contains CfTX-1 and CfTX-2 — potent pore-forming toxins that create holes in cell membranes, leading to massive ion flux (potassium release, calcium influx), myocardial depression, and cardiovascular collapse; hyperkalemia is a major mechanism of death
• Vinegar (4-6% acetic acid) is the recommended first aid for C. fleckeri stings as it inactivates undischarged nematocysts; this is specific to box jellyfish — for other jellyfish species (e.g., Physalia/bluebottle), hot water immersion (45°C for 20 minutes) is preferred
• CSL Box Jellyfish Antivenom should be administered IV for severe envenomation; it neutralizes circulating venom but cannot reverse tissue damage already sustained; early administration is critical
• Prevention is paramount in endemic areas: stinger nets at beaches, full-body lycra stinger suits, awareness of seasonal risk (October-May in northern Australia), and heeding beach warning signs and closures

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