How are red blood cell cyanide concentrations assessed in the diagnosis of cyanide toxicity?

Updated: May 30, 2020
  • Author: Inna Leybell, MD; Chief Editor: Michael A Miller, MD  more...
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Cyanide blood concentrations are not generally available in time to aid in the treatment of acute poisoning, but may provide subsequent confirmation. In cyanogen exposures, these tests provide documentation for therapeutic use, which may last several days.

The preferred test is a red blood cell cyanide concentration. With this method, mild toxicity is observed at concentrations of 0.5-1.0 μg/mL. Concentrations of 2.5 μg/mL and higher are associated with coma, seizures, and death. Blood cyanide concentrations may artificially increase after sodium nitrite (antidote) administration, because of in vitro release of cyanide from cyanomethemoglobin during the analytical procedure by strong acid used in analysis.

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