Sea wasp sting

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Box jellyfish (Chironex fleckeri)
Nematocyst stages of discharge
  • Chironex fleckeri, commonly known as sea wasp
  • Large form of box jellyfish, found mostly off the coast of northern Australia to the Philippines
  • Extremely deadly, often considered one of the most poisonous jellyfish
  • Identification: Often difficult to distinguish in environment, as animal is transparent. Pale blue bell, often the size of a basketball, with 15 tentacles emerging from lower corners up to 3 meters in length. Has been described as having an eerie similarity to a human skull
  • Tentacles contain millions of stinging cells known as cnidocytes

Clinical Features

  • Sting is extremely painful, described as burning, and can cause death as quickly as 3-5 minutes
  • Can cause significant hypotension, hypertension, cardiac arrhythmia, and cardiac arrest
  • Most stings are mild and are self-limiting
  • Deaths most commonly occur in children
  • Venom causes cells to become leaky, causing hyperkalemia

Differential Diagnosis

Marine toxins and envenomations


  • Assess/manage ABCs
  • ECG (look for arrhythmia, blocks, ischemia)
  • CXR
  • CBC, BMP, troponin/CK
  • Consider:
    • ABG, echo, nematocyst sampling


  • Address ABCs (e.g. CPR, fluid resuscitation, vasopressors, intubation as needed]]
  • Remove tentacles!!!
    • Nematocysts can continuing firing and delivering more venom if tentacles still attached
    • If available, pour lots of vinegar over tentacles first to inactivate
  • Do NOT apply pressure dressing/immobilization (triggers nematocysts to fire)
  • Box Jellyfish antivenom, if available
    • Cardiac arrest: 6 ampules IV push
    • Systemic envenomation with hypotension, collapse, or significant arrhythmia: 3 ampules in 100mL NS over 20m
    • Pain refractory to opioids: 1 ampule in 100mL NS over 20m
  • Magnesium sulfate: 10 mmol (~2-3g) IV if hemodynamically unstable


See Also