Pediatric emergency medicine trisk 2000 2000
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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.
