UMEM Educational Pearls

Category: Toxicology

Title: Diagnosing Cyanide Poisoning with Lab Tests

Keywords: cyanide, lactate (PubMed Search)

Posted: 9/9/2010 by Bryan Hayes, PharmD (Updated: 12/9/2022)
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In the setting of acute cyanide poisoning, it is virtually impossible to obtain a timely cyanide level to help assess toxicity.  However, there are two diagnostic tests that can help confirm your diagnosis.

  1. Anion gap metabolic acidosis with elevated lactate
  2. Narrowing of the venous-arterial PO2 gradient

Remember cyanide halts cellular respiration meaning the cells cannot utilize oxygen.  Therefore, the venous PO2 should be about the same as the arterial PO2.  The cells then switch to anaerobic metabolism, thereby producing lactate.