Pediatric emergency medicine trisk 4580 4580
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concentration. The recommended initial pediatric dosage, assuming hemoglobin
concentration of 12 g/dL, is 0.33 mL/kg of the standard 3% sodium nitrite
solution, given slowly IV over 5 to 10 minutes; the initial adult dosage is 10 mL.
Thiosulfate itself is efficacious, relatively benign, and also synergistic with
oxygen administration. The initial thiosulfate dose for children is 1.65 mL/kg of
the standard 25% solution IV, and the initial adult dose is 50 mL. Second
treatments with one-half the initial dose of nitrite and thiosulfate may be given 30
minutes after the original dose if needed in severe cases.
The newer antidote available in the United States is hydroxocobalamin,
available in Cyanokit. This compound nonenzymatically and reversibly reacts
with cyanide to form cyanocobalamin (vitamin B12 ) which is subsequently
excreted. It does not induce hypotension (in fact, it predictably raises the blood
pressure) or methemoglobinemia and has been advocated as a replacement for the
cyanide antidote kit, especially for smoke-inhalation victims. However, the
cyanide antidote kit has a well-documented record of efficacy. Moreover,
hydroxocobalamin must be given via the IV route; amyl nitrite, included in the
cyanide antidote kit, can be given via inhalation to a patient without IV access.
The recommended initial dose of hydroxocobalamin is 5 g in adults or 70 mg/kg
in children, administered IV over 15 minutes (∼15 mL/min). A second 5-g dose
(70 mg/kg in children) may be repeated in severely affected patients, with the
second infusion rate ranging from 15 minutes to 2 hours based on the condition of
the patient. The medication is dark red in color, and treatment results in reddening
of skin and mucous membranes and red-colored urine that may last several days.
This phenomenon may also skew some common laboratory results that are based
on colorimetric tests, such as creatinine, bilirubin, and hepatic transaminases, as
well as cooximetry results.
To date, the superiority of one cyanide antidote over another has not been
clearly demonstrated. Newer compounds with oral availability are under
investigation and include cobinamide, a cobalamin precursor with high cyanide
affinity, and analogs of 3-methyl pyruvate, which like thiosulfate enhance
conversion of cyanide to thiocyanate. Because clinical distinction between
cyanide and nerve-agent casualties may be difficult, any patient thought to have
been exposed either to cyanide or to a nerve agent but who does not respond to
antidotal therapy specific for the suspected agent should be given a trial of the
antidotes for the other agent.
Riot-Control Agents
