Pediatric emergency medicine trisk 4579 4579
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Management of cyanide poisoning begins with removal to fresh air. Dermal
decontamination is unnecessary if exposure has been only to vapor, but wet
clothing should be removed and the underlying skin should be washed with soap
and water. Attention to the basics of intensive supportive care is critical and
includes administration of 100% oxygen to all significantly symptomatic patients,
mechanical ventilation as needed, circulatory support with crystalloid and
vasopressors, correction of metabolic acidosis with IV sodium bicarbonate, and
seizure control. The cyanide-induced inhibition of cellular oxygen use might lead
to the expectation that supplemental oxygen would not be of use in cyanide
poisoning, but in fact, administration of 100% oxygen has been found to
empirically exert a beneficial effect, possibly by affecting the interaction of
cyanide with nitric oxide in mitochondria.
Symptomatic patients, especially those with severe manifestations, may further
benefit from specific antidotal therapy. Currently, two regimens are available in
the United States. The first, the original “cyanide antidote kit” utilizes a two-step
process. First, a methemoglobin-forming agent such as amyl nitrite or sodium
nitrite is administered. This causes dissociation of bound cyanide from the
cytochrome oxidase and restores aerobic energy production. Perhaps even more
importantly, nitrites generate nitric oxide, which antagonizes the inhibition of
cytochrome oxidase by cyanide. The second step of the cyanide antidote kit is
provision of a sulfur donor, sodium thiosulfate, which reacts irreversibly with
cyanide to generate thiocyanate and sulfites, both of which are excreted in the
urine.
Caution is warranted when using this cyanide antidote. Nitrites result in
vasodilation, which may enhance vital organ perfusion. However, too rapid
infusion may cause or exacerbate hypotension, and overproduction of
methemoglobin may compromise oxygen-carrying capacity. Thus, this therapy
should be avoided in conscious patients with minimal symptoms and used with
caution in patients, especially children, whose cyanide toxicity may be
complicated by carbon monoxide poisoning (e.g., smoke-inhalation victims).
However, a case study of adult smoke-inhalation victims treated with nitrites and
sodium thiosulfate showed no complications of the nitrite therapy, and smoke
inhalation should be regarded as a relative rather than an absolute
contraindication to nitrite use.
The nitrite risk–benefit ratio becomes more favorable in the context of a
severely intoxicated casualty of a terrorist cyanide vapor attack, and careful
attention to proper dosing and rate of administration should allow safe use of this
antidote. Pediatric nitrite dosing depends on body weight and hemoglobin
