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 8 years. For children younger than 8 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
do 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