Nematocysts

Background

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

  • Coral reef

  • Portuguese Man-O-War {Physalia physalis)

  • A selection of various sea anemones


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

Skin lesion after contact with the cubomedusa Chiropsalmus quadrumanus jellyfish

==Irukandji syndrome==[1]

  • Usually develops within 2 hours of envenomation & can last up to 2 days
  • Rare but potentially fatal complication can manifest in diverse ways:
    • Myalgias
    • Back pain
    • Chest pain
    • Abdominal pain
    • Nausea and vomiting
    • Diaphoresis
    • Hypertensive crisis
    • Cardiogenic pulmonary edema
    • Intracranial hemorrhage
    • Death

Differential Diagnosis

Marine toxins, envenomations, and bites

Evaluation

  • Generally a clinical diagnosis

Management

  • Remove tentacles and nematocysts
  • Hot salt water immersion (inactivates heat labile toxins), submerging the area in 45 ℃ water for 20 minutes has been shown to provide significant pain relief[2]
  • Consider topical lidocaine
  • Consider oral or parenteral analgesia for severe pain
  • In general, avoid acetic acid (vinegar) since it mostly increases the firing of nematocysts and therefore increases pain.[3]
    • Some evidence that it does inhibit nematocyst discharge in the Australian Box Jellyfish species [4]
      • Box Jellyfish: 4-5% acetic acid solution should be applied to the injured area for at least 30 seconds.[5]
  • Symptomatic treatment for Irukandji syndrome
  • Antivenom is available for severe box jellyfish sting

Avoid

  • Urine, ethanol, ammonia,
  • Acetic acid/vinegar (unless box jellyfish) [6]
  • 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
  1. ↑ Hauglid, C., Kiel, J., & Schmidt, A. (2021, April 23). Emergen-Sea Medicine: Overview of Marine Envenomations - Page 4 of 5. ACEP Now. https://www.acepnow.com/article/emergen-sea-medicine-overview-of-marine-envenomations/4/.
  2. ↑ #Isbister GK, Currie BJ. Hot water immersion v icepacks for treating pain of Chironex fleckeri stings: a randomised controlled trial. Med J Aust. 2017 Oct 16;207(8):362. PubMed PMID: 29020913.
  3. ↑ Hauglid, C., Kiel, J., & Schmidt, A. (2021, April 23). Emergen-Sea Medicine: Overview of Marine Envenomations - Page 4 of 5. ACEP Now. https://www.acepnow.com/article/emergen-sea-medicine-overview-of-marine-envenomations/4/.
  4. ↑ Yanagihara AA, Wilcox CL. Cubozoan Sting-Site Seawater Rinse, Scraping, and Ice Can Increase Venom Load: Upending Current First Aid Recommendations. Toxins (Basel). 2017;9(3):105. Published 2017 Mar 15. doi:10.3390/toxins9030105
  5. ↑ Hauglid, C., Kiel, J., & Schmidt, A. (2021, April 23). Emergen-Sea Medicine: Overview of Marine Envenomations - Page 4 of 5. ACEP Now. https://www.acepnow.com/article/emergen-sea-medicine-overview-of-marine-envenomations/4/.
  6. ↑ Hauglid, C., Kiel, J., & Schmidt, A. (2021, April 23). Emergen-Sea Medicine: Overview of Marine Envenomations - Page 4 of 5. ACEP Now. https://www.acepnow.com/article/emergen-sea-medicine-overview-of-marine-envenomations/4/.
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