Pediatric emergency medicine trisk 500

Current evidence. Stingrays are the most important group of venomous fishes,
accounting for an estimated 1,000 attacks per year in North America. Stingrays
are bottom feeders that bury themselves in sand or mud of bays, shoal lagoons,
and river mouths. They are found along the Atlantic, Pacific, and Gulf coasts and
range from several inches in diameter to more than 14 ft in length. Six different
species are represented in North American waters. Envenomations usually occur
when an unsuspecting swimmer steps on the back of the animal and causes it to
hurl its barbed tail upward into the victim as a reflex defense response. Most
injuries are confined to the lower extremities, although wounds to the chest and
abdomen have been reported.
The venom apparatus consists of a serrated, retropointed, dentinal caudal spine
located on the dorsum of the tail. Spines vary in length, depending on the size of
the ray, but may reach a length of 122 cm in some species. The spine is encased
in an integumentary sheath that contains specialized secretory cells that hold the
venom. When the stingray’s barb strikes the victim, it easily penetrates the skin,
rupturing the integumentary sheath over the spine and causing the venom to pass
along the ventrolateral grooves of the barb, into the wound. The barb is
retropointed, so the wound it produces is a combination of puncture and
laceration. Wounds may vary in length from 3.5 to 15 cm. Life-threatening
puncture wounds may occur that require immediate resuscitation. The venom is a
heat-labile toxin that depresses medullary respiratory centers, interferes with the
cardiac conduction system, and produces severe local pain.
The sting is followed immediately by pain, which spreads from the site of
injury during the next 30 minutes, peaks within 90 minutes, and lasts up to 48
hours. Syncope, weakness, nausea, and anxiety are common complaints due to
effects of the venom and the vagal response to the pain. Vomiting, diarrhea,
sweating, and muscle fasciculations of the affected extremity may also occur.
Generalized cramps, paresthesias, hypotension, arrhythmias, and death may
occur. The wound often has a jagged edge that bleeds profusely, and the wound
edges may be discolored. Discoloration may extend several centimeters from the
wound within hours after injury and may subsequently necrose if untreated.

Often, parts of the stingray’s integumentary sheath contaminate the wound.
Treatment is aimed at treating shock, direct pressure to control bleeding,
preventing complications of the venom, alleviating pain, and preventing
secondary infection. At the scene, the wound should be irrigated with cold
saltwater as this can remove much of the venom. Remnants of the integumentary
sheath should be removed if it can be seen in the wound. The extremity should be
placed in hot water (40° to 45°C [104° to 113°F]) for 30 to 90 minutes. After


soaking, the wound should be reexplored, debrided again if necessary, and
potentially closed, although delayed primary closure is preferred. Imaging can be
obtained to rule out retained spines. Pain relief is best achieved with morphine,
local anesthetic infiltration, or a nerve block. Tetanus prophylaxis should be
considered, but antibiotics are reserved for wounds that become secondarily
infected.

Sharks
Shark attacks may be preceded by one or more “bumps,” which may cause
extensive abrasions from the rough denticles of the shark’s skin. Two types of bite
wounds are described: tangential injury and a definitive bite. Tangential injury,
caused by the slashing movement of the open mouth as the shark makes a close
pass, causes severe lacerations, incised wounds, and loss of tissue. Definitive bite
wounds cause lacerations, loss of soft tissue, amputations, and comminuted
fractures. Most injuries involve only one or two bites and are confined to the
extremities.
Hypovolemic shock is the immediate threat to life in shark attacks. Bleeding
should be controlled at the scene with direct compression, and intravascular
volume should be replaced with crystalloid until blood products are available.
The victim should be kept warm and given oxygen when being transported to an
ED. Wounds should not be explored in the field. Tetanus immunization should be

considered, and prophylactic antibiotics with a third-generation cephalosporin or
trimethoprim-sulfamethoxazole is recommended.

Scorpaenidae
The 80 species found in the Scorpaenidae family include the zebra fish, scorpion
fish proper, and stonefish. In California, the sculpin is commonly involved.
Scorpaenidae are generally found in shallow water, around reefs, kelp beds, or
coral. They are nonmigratory, slow swimming, and often buried in sand. The
venom apparatus consists of a number of dorsal, anal, and pelvic spines covered
by integumentary sheaths containing venom glands that lie within anterolateral
grooves. The venoms are unstable, heat-labile compounds. Most often
envenomation occurs when the fish are handled during fishing excursions.
Severe pain at the site of the wound is the first and primary clinical sign for all
species. The wound and surrounding area becomes ischemic and then cyanotic.
Paresthesia and paralysis of the extremity may occur. Other clinical signs include
nausea, vomiting, hypotension, tachypnea proceeding to apnea, and myocardial
ischemia with electrocardiographic changes. In cases of serious envenomation,


pain can persist for hours or even days and the emergency provider should
provide adequate analgesia.
Treatment involves irrigating the wound with sterile saline. The injured
extremity is then immersed in very hot water (40° to 45°C [104° to 113°F]) for 30
to 60 minutes or until the agonizing pain is completely relieved. Pain relief is best
achieved with morphine 0.1 mg/kg IV, IM, or SC. The patient should be
monitored carefully for cardiotoxic effects and respiratory depression. Antivenin
is available only for the stings of the stonefish of Australia.

Catfish
The catfish is a popular food and sport fish found in many lakes and rivers

throughout the United States. The venom apparatus consists of a number of
spines located in the dorsal and pectoral fins. The integumentary sheaths covering
the spines contain venom glands. The venoms are unstable, heat-labile
compounds.
Injuries can be a combination of puncture wounds and lacerations, foreignbody reactions, and the effects of venom. The spines may become imbedded in
flesh, causing soft tissue swelling, infection, or foreign-body reaction. The venom
produces a local inflammatory response with local intense pain, edema,
hemorrhage, and tissue necrosis.
Treatment involves irrigating the wound with sterile saline. The injured
extremity is then immersed in hot water (40° to 45°C [104° to 113°F]) for 30 to
60 minutes or until pain is relieved. Pain relief is best achieved with morphine.
The wound should be explored, spines removed and debrided if needed. Systemic
antibiotics to cover gram-negative organisms are recommended. Wounds may be
closed by using a delayed primary closure.

TERRESTRIAL INVERTEBRATES
Phylum Arthropoda
The arthropods make up the largest phylum in the animal kingdom. All
arthropods have an exoskeleton with jointed appendages. The phylum is divided
into two subphyla: the Chelicerata, which includes scorpions, spiders, ticks, and
mites, and the Mandibulata, which includes insects.
Scorpions
There are 650 known scorpion species (class Arachnida), but only a limited
number are dangerous to humans. In the southwest United States, Centruroides
sculpturatus is the potentially lethal inhabitant. Although C. sculpturatus and


Centruroides exilicauda have been considered separate species in the past, more
recent taxonomic classification treats the two as one species. It has two pinching
claws anteriorly and a tail or pseudoabdomen that ends in a telson ( Fig. 90.16 ),

that houses a pair of poison glands and a stinger. The animals are nocturnal;
during the day they seek shelter under stones and debris. They often crawl into
sleeping bags, shoes, and unoccupied clothing.
The scorpion produces a neurotoxin and a local cytotoxin. The neurotoxin (αtoxin) inhibits the inactivation of the voltage-gated sodium channels, which leads
to prolonged depolarization and neuroexcitation affecting the autonomic and
skeletal neuromuscular system. Scorpion α-toxins also result in massive
endogenous release of catecholamines and vasoactive peptide hormones, such as
neuropeptide Y and endothelin-1. An estimated 10% of stings result in severe
systemic envenomation. Common symptoms include local pain, restlessness,
hyperactivity, roving eye movements, and respiratory distress. Other associated
signs may include convulsions, drooling, wheezing, hyperthermia, cyanosis,
abdominal pain, vomiting, GI hemorrhage, and respiratory failure. Death may
result from respiratory paralysis, pulmonary edema, or cardiogenic shock. The
diagnosis may be difficult because history of a sting may not be forthcoming
especially since most bites involve children <10 years old. There is no laboratory
test for confirmation of scorpion envenomation.
Treatment begins with general supportive care. Cryotherapy at the site of the
sting has been advocated to reduce swelling and local induration. Anascorp is the
first ever FDA-approved scorpion antivenom that is available in the U.S. market.
Although the use of antivenom remains controversial, clinical studies have shown
that in children it reverses signs of scorpion envenomation and length of
hospitalization. Prazosin (an α1 -blocker) has also been used, and dobutamine
might be beneficial to patients with cardiodepressive effects. Calcium gluconate
(0.1 mL/kg [10 mg/kg] of the 10% solution) has been given intravenously to
reduce muscular contractions and associated pain, but benefit has not been
proven. Sedative anticonvulsants, in particular, phenobarbital (5 to 10 mg/kg) or
benzodiazepines (midazolam 0.05 to 0.1 mg/kg) intravenously are used to treat
persistent hyperactivity, convulsions, and/or agitation. A continuous infusion of
midazolam may optimize treatment in extreme cases (start at 0.1 mg/kg/hr and
titrate to relief of symptoms). Corticosteroids and antihistamines have little, if

any, proven benefit. There are only limited data about the safety of antivenom in
pregnant women, and it should be used with caution and only in those patients
with systemic symptoms.