Pediatric emergency medicine trisk 4577 4577
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Initial effects after mild to moderate exposures to chlorine include ocular and
nasal irritation, followed by cough, and progressing to a choking sensation and
substernal chest tightness. Bronchospasm often occurs, especially in patients with
a history of reactive airway disease. Pulmonary edema may develop within 30
minutes to 4 hours depending on the severity of exposure.
Mild to moderate exposures to phosgene may be initially asymptomatic with
only the perception of a pleasant odor of newly mown hay. Thus, lung-exposure
time may be significant before victims remove themselves from the affected area.
Pulmonary edema occurs after a considerable delay, typically 4 to 6 hours, but up
to 24 hours after low concentration exposures. In these cases, delayed-onset
shortness of breath or chest tightness precedes objective clinical or radiologic
findings. With high concentration exposures, early lacrimation may be followed
by cough, dyspnea, and pulmonary edema. The pulmonary edema may be so
severe as to result in hypotension from hypovolemia. The onset of shortness of
breath or chest tightness within the first 4 hours of exposure to phosgene portends
the eventual development of massive pulmonary edema and a grave prognosis.
Management of exposure to pulmonary agents is primarily supportive.
Removal to fresh air generally suffices for decontamination. Careful attention to
control of pulmonary secretions, bronchospasm, and pulmonary edema as well as
to aggressive treatment of secondary bacterial infection (often occurring 3 to 5
days after exposure) is required. Animal studies suggest a modest benefit of
steroid therapy in mitigating lung injury after chlorine inhalation; thus steroids
may be considered for patients with chlorine exposure, especially as an adjunct to
bronchodilators. In addition, some symptomatic relief has also been reported for
chlorine exposure with nebulized 3.75% sodium bicarbonate therapy, but the
impact of this regimen on pulmonary damage is unknown.
Cyanide
Compounds containing the cyanide ion (CN− ) have a long history as favored
agents for homicide and suicide, but their efficacy as CWAs is limited by their
volatility in open air and by their flammability. However, if released
nonexplosively in a crowded, closed room, they could have devastating effects.
Chemical agents containing cyanide include the liquids hydrocyanic acid
(hydrogen cyanide, HCN; NATO Code AC) and cyanogen chloride (ClCN;
NATO code CK), both of which rapidly vaporize after release.
Toxicology
Some cyanide is normally present in human tissues and several pathways exist for
its metabolism. For example, cyanide reacts reversibly with metals such as ferric
