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Marine Envenomations

Mizuho Morrison, DO, Matthieu DeClerck, MD, and Aaron Bright, MD
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16:06

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Knowing management of types of marine envenomations is important. Matt Declerk Wilderness medicine expert discusses with us importance of wound care and management of common ocean water stings.

Pearls:

  • The sting of a jellyfish comes from venom released by the nematocyst.  Treatment is focused on inactivating and removing the nematocyst to prevent further release of venom.

  • Stingray stings cause two types of injuries: penetrating injury from the barb, and injury from the envenomation.

  • Inactivate stingray venom with hot water.

 

JELLY FISH

  • The stinging organelle of a jellyfish is called a nematocyst.  Each tentacle has thousands of microscopic nematocysts.  The nematocyst is a capsule with a venom sac and a tubule with a barb-laden end that is coiled up like a spring.  Externally there is a mechanical trigger.  When a fish or a your hand presses on the trigger, the barb shoots out into your skin releasing the venom very quickly.  

  • The type of venom varies depending on the species of jellyfish.  Some are cardiotoxic, neurotoxic, and some have dermatonecrotic compounds.  

  • Patients present after a jellyfish sting with a variety of complaints including pain, burning and itching, and skin findings including erythema, wheels, vesicular formations, hypo or hyperpigmentation and even superficial necrosis.

  • The pain of a jellyfish sting can last for days to weeks and patients can have a delayed hypersensitivity reaction.  

  • Patients can have minor dermatologic effects or systemic symptoms including tachycardia, hypotension, sweating, piloerection, agitation and, though uncommon, cardiac complications.  Severe anaphylactic reactions, though rare, are possible.  

  • Treatment:

    • After a sting, victims get out of the water and continue to have pain because the tentacles are very sticky and are still on the skin.  

    • The goal is to inactivate the remaining nematocysts before you remove them so that you don’t trigger them to fire and cause more pain as you remove them.

    • There are  many different types of jellyfish species and we do not have good evidence to guide our therapy.  People have historically tried acetic acid (vinegar), urine (also acidic), meat tenderizer, and countless other old wives tails.  

      • Li L, et al. Interventions for the symptoms and
        signs resulting from jellyfish stings. Cochrane Database Syst Rev. 2013 Dec 9;(12):CD009688. PMID: 24318773

        • Looked at 7 clinical trials with 433 participants.  

        • Hot water immersion was found to be superior to ice packs in achieving pain relief at 10 minutes and 20 minutes.  

        • Vinegar made the skin appearance worse.

    • If you have tentacles on you, and don’t have vinegar or hot water around to try, your best bet is probably to hose the tentacles off.  Brushing them off with your hand will cause your hand to be stung as well.  The pressure of the water will likely be enough to get the tentacles off, and the fresh water may be effective in inactivating the salt-water loving nematocysts.

    • Aftercare treatment is focused on pain control.  NSAIDS are usually sufficient, but severe stings may require opiates.  Topical steroids can decrease inflammation.  There is no need for prophylactic antibiotics unless an infection develops, but the nematocysts do not typically break the skin barrier and so these are not typically infection-prone wounds.  

 

STINGRAYS

  • There are about 2000 stingray stings in the US each year.

  • Stingrays like shallow water where it is warm and the most common sting sites are on the foot and ankle from stepping on a stingray in the sand.  

  • The stinger has several barbs that help it stick in the skin and a venom sack that gets injected.

  • This means that medical evaluation of stingray stings is twofold:

    • First, the penetrating injury.  How deep did it penetrate and what important structures are nearby?

    • Second, the envenomation.  It is possible to have an anaphylactic reaction to the venom, but this is rare.  Typically patients experience a localized, painful reaction.  

  • Treatment is also twofold:

    • Is the barb still inside? If it is, it is like any other foreign body and is at high risk for infection.  They can be radiopaque, so sometimes can be seen on x-ray.  If there is an infected sting site with no barb seen on x-ray, you may have to obtain an MRI to determine if there is a barb imbedded.  

    • The venom is protein-based and heat-labile, so will respond well to hot water.  Shoot for a temperature of about 55 degrees Celsius (122 degrees Fahrenheit).  Be careful about causing a second degree burn with too hot water.

This is a very infection prone wound, so consider prophylactic antibiotics, particularly if you are not sure if there is a barb remaining inside.    

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