Nematocysts

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Background

  • Jellyfish; box jellyfish is most deadly
  • Most toxic: Australia and other Indo-Pacific waters

Mechanism

Nematocyst stages of discharge
  • Physical contact or osmotic gradient causes discharge of nematocysts
  • A spring loaded venom delivery system
  • Once opened, a nematocyst releases all of its contained venom

Clinical Features

  • Isolated stinging
  • Severe
    • Respiratory paralysis
    • Cardiovascular collapse
    • Limb paralysis
    • Death

Irukandji syndrome

Differential Diagnosis

Marine toxins and envenomations

Evaluation

  • Generally a clinical diagnosis

Management

  • Remove tentacles and nematocysts
  • Hot salt water immersion (inactivates heat labile toxins)
  • Consider topical lidocaine
  • Consider oral or parenteral analgesia for severe pain
  • Acetic Acid may inhibit or trigger nematocyst discharge and thereby increase or decrease pain depending on species (can use fruit juice or other flavored sodas if vinegar not available)
  • Symptomatic treatment for Irukandji syndrome
  • Antivenom is available for severe box-jellyfish sting

Avoid

  • Urine, ethanol, ammonia
  • Fresh or tap water (causes nematocyst discharge via the osmotic gradient)

Disposition

See Also

References

  1. Ward NT, Darracq MA, Tomaszewski C, et al. Evidence based treatment of jellyfish stings in North America and Hawaii. Ann Emerg Med. 2012;60(4):339-414.
  2. Cegolon L, Heymann WC, Lange JH, et al. Jellyfish stings and their management: a review. Mar Drugs. 2013;11(2): 523-50