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Hot-Water Immersion or Ice Packs as First Aid for Cnidarian Envenomations?

An article from Toxins about the most effective treatments for cnidarian envenomations has been attracting attention in the first-aid community. You can download the article for free and read it for yourself:

Heated Debates: Hot-Water Immersion or Ice Packs as First Aid for Cnidarian Envenomations?

Abstract: Cnidarian envenomations are an important public health problem, responsible for more deaths than shark attacks annually. For this reason, optimization of first-aid care is essential. According to the published literature, cnidarian venoms and toxins are heat labile at temperatures safe for human application, which supports the use of hot-water immersion of the sting area(s). However, ice packs are often recommended and used by emergency personnel. After conducting a systematic review of the evidence for the use of heat or ice in the treatment of cnidarian envenomations, we conclude that the majority of studies to date support the use of hot-water immersion for pain relief and improved health outcomes.

Another paper, also from Toxins investigates the effects of vinegar on live tentacles:

Experimental Assays to Assess the Efficacy of Vinegar and Other Topical First-Aid Approaches on Cubozoan (Alatina alata) Tentacle Firing and Venom Toxicity

Abstract: Despite the medical urgency presented by cubozoan envenomations, ineffective and contradictory first-aid management recommendations persist. A critical barrier to progress has been the lack of readily available and reproducible envenomation assays that (1) recapitulate live-tentacle stings; (2) allow quantitation and imaging of cnidae discharge; (3) allow primary quantitation of venom toxicity; and (4) employ rigorous controls. We report the implementation of an integrated array of three experimental approaches designed to meet the above-stated criteria. Mechanistically overlapping, yet distinct, the three approaches comprised (1) direct application of test solutions on live tentacles (termed tentacle solution assay, or TSA) with single image- and video-microscopy; (2) spontaneous stinging assay using freshly excised tentacles overlaid on substrate of live human red blood cells suspended in agarose (tentacle blood agarose assays, or TBAA); and (3) a “skin” covered adaptation of TBAA (tentacle skin blood agarose assay, or TSBAA). We report the use and results of these assays to evaluate the efficacy of topical first-aid approaches to inhibit tentacle firing and venom activity. TSA results included the potent stimulation of massive cnidae discharge by alcohols but only moderate induction by urine, freshwater, and “cola” (carbonated soft drink). Although vinegar, the 40-year field standard of first aid for the removal of adherent tentacles, completely inhibited cnidae firing in TSA and TSBAA ex vivo models, the most striking inhibition of both tentacle firing and subsequent venom-induced hemolysis was observed using newly-developed proprietary formulations (Sting No More™) containing copper gluconate, magnesium sulfate, and urea.

First aid implications

Taken together, these two papers provide a two-step evidence-based update to cnidaria sting first-aid treatment:

  1. Vinegar rinse for live tentacle and shed cnidae removal. Vinegar safely prevents both chemically- and pressure-induced cnidae discharge and does not increase venom load, but decreases it, as demonstrated by a live red blood cell agar assay.
  2. Hot-water immersion for pain relief and improved health outcomes.

Further, evidence points to the efficacy of a new copper gluconate based cream to reduce venom based destruction of red blood cells and tissue.

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