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