Pediatric emergency medicine trisk 499

Phylum Coelenterata (Cnidaria) The phylum is divided into three large classes: Hydrozoa (hydras, Portuguese man-of-war), Scyphozoa (true jellyfish), and Anthozoa (soft corals, stone corals, anemones) Coelenterata have tentacles with specialized organelles called nematocysts, which are used for entangling, penetrating, anchoring, and poisoning prey ( Fig 90.15 ) When the tentacles touch an object, the nematocysts fire, releasing toxin-coated, barbed threads The severity of envenomation is related to venom toxicity, number of nematocysts discharged, and general condition of the victim Stings from sessile forms are generally not as severe as stings from free-floating forms Jellyfish venoms affect autonomic nervous systems via several mechanisms Paralysis and CNS effects appear to be related primarily to toxic proteins and peptides Burning pain and urticaria are caused by the release of various mediators of inflammation, including serotonin and histamine FIGURE 90.15 Marine invertebrate causing human sting Class Hydrozoa Feathered hydroid (Pennaria tiarella ) is found from Maine to Florida and along the Texas coast just below the low-tide line They attach to solid objects, including pilings and floats They cause a mild sting that may be treated with local care Portuguese man-of-war (Physalia physalis ) is a hydrozoan colony, although it is commonly erroneously considered a jellyfish The float can be up to 30 cm in length, with tentacles hanging from the float that may reach more than 75 ft in length and contain about 750,000 nematocysts each This open-sea animal is often driven ashore by storms along the Atlantic coast Tentacles on the skin should be fairly easy to recognize as the cause of symptoms Releasing one of the most powerful marine toxins, the nematocysts of the Portuguese man-of-war may discharge even when it is dead and washed up on the beach Because of the length and transparency of the tentacles in the water, swimmers are often stung without seeing the animal The toxin contains polypeptides and degradative enzymes Local effects include pain and irritation Systemic reactions include headache, myalgias, fever, abdominal rigidity, arthralgias, nausea, vomiting, pallor, respiratory distress, hemolysis, renal failure, and coma Death may occur if the area stung is extensive in relation to the size of the victim The unexploded nematocysts are inactivated with topical application for 30 minutes with vinegar (3% acetic acid), a slurry of baking soda, or meat tenderizer (papain) Papain should not be left on for more than 15 minutes Vinegar is generally the best disarming agent for hydrozoan stings; however, for Portuguese man-of-war, vinegar may be ineffective and may sometimes paradoxically activate the nematocysts The affected area should be washed with seawater or normal saline and if Portuguese man-of-war sting is suspected it should be dipped in hot seawater (40° to 45°C [104° to 113°F]) for 20 minutes The affected limbs should be immobilized There is no antivenin available for Physalia or the scyphozoans, with the exception of the sea wasp, Chironex fleckeri, of Australia Shock may require cardiorespiratory support General supportive measures for systemic reactions include antihistamines, corticosteroids, and opiates for pain Muscle spasms have been treated with 10% solution of calcium gluconate 0.1 mL/kg (10 mg/kg) given intravenously, although the efficacy is controversial Local dermatitis should be treated with a topical corticosteroid cream, and topical treatment with 1% lidocaine is effective in pain control Class Scyphozoa The common purple jellyfish (Pelagia noctiluca ) is only mildly toxic Local skin irritation is the major clinical manifestation Sea nettle (Chrysaora quinquecirrha ) is a common jellyfish found along the Atlantic coast Clinical manifestations are the same as those for purple jellyfish Lion’s mane (Cyanea capillata ) is a highly toxic creature that can reach a width of 244 cm, with tentacles as long as 61 cm The animal is found along both coasts Contact with the tentacles produces severe burning Prolonged exposure causes muscle cramps and respiratory failure Treatment of scyphozoan stings is the same as above for hydrozoan stings Class Anthozoa The anemones found within United States tidal zones are only mildly toxic Coral cuts and stings can be a problem for swimmers off the Florida coast The stinging ability of stony corals is minor; coral cuts can be severe due to a combination of lacerations, nematocyst venom, foreign debris in the wound, and secondary bacterial infection The clinical picture is one of stinging sensation followed by wheal formation and itching If the wound is untreated, an ulcer with an erythematous base may form within a few days Cellulitis, lymphangitis, fever, and malaise may occur Treatment consists of cleaning the wound and irrigation with copious amounts of saline, removal of foreign particles, and debridement Marine bacteria that can inoculate wounds are generally heterotrophic, motile, and facultatively anaerobic, gram-negative rods Organisms include Vibrio species, Erysipelothrix rhusiopathiae, and Mycobacterium marinum Wounds should be left open Broadspectrum antibiotic therapy, particularly tetracycline, at a dosage of 40 mg/kg/day in four divided doses, has been advocated but should not be used routinely in children younger than years For children younger than years, cephalexin (50 mg/kg/day in four divided doses) or trimethoprim-sulfamethoxazole (10 mg TMP/kg/day divided in two doses) should be used Phylum Echinodermata Phylum Echinodermata includes starfish, sea urchins, and sea cucumbers Of the three classes, only the Echinoidea (sea urchins) have clinical relevance for U.S children The long-spined urchins (e.g., Diadema) are dangerous to handle They not appear to possess venom like tropical urchins, but the spines, composed of calcium carbonate, easily pierce the skin, wet suits, and sneakers and can lodge deep into flesh Most injuries occur during wading in shallow water Penetration of skin by spines is accompanied by intense pain followed by redness, swelling, and aching The venom has hemolytic, myonecrotic, hepatotoxic, and anticoagulant properties Complications include tattooing of the skin, joint arthritis, secondary infection, and granuloma formation Management All spines should be removed as completely as possible using local anesthetic if needed Radiography and ultrasound may be used for spine localization and removal Any spines not reachable will be absorbed in time, but granulomas from retained spine fragments may require excision Soaking in warm water may be helpful for pain Systemic antistaphylococcal antibiotics should be used if signs of infection develop In case of reactive neuropathy, systemic corticosteroids are recommended MARINE VERTEBRATES Stingrays