UMEM Educational Pearls

Category: Toxicology

Title: Utility of lactic acid level for diagnosis of cyanide poisoning in smoke inhalation victims

Keywords: cyanide toxicity, lactic acid (PubMed Search)

Posted: 12/29/2016 by Hong Kim, MD (Emailed: 12/30/2016) (Updated: 12/30/2016)
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Smoke inhalation victims (house fires) are at risk of carbon monoxide (CO) and cyanide poisoning (CN). CO exposure/poisoning can be readily evaluated by CO - Oximetry but CN level can be obtained in majority of the hospital.

Lactic acid level is often sent to evaluate for CN poisoning.


Bottom line:

  1. Lactatic acid levels should be sent in all smoke inhalation victims.
  2. Elevate lactate > 10 mmol/L is highly suggestive of CN poisoning




In a manuscript published in 1991, N Engl J Med by Dr. FJ Baud is the source of this data.

CN blood levels were measured in 109 residetial fire victims in France prior to any treatment was initiated.

  • 43 fire victims who died had mean blood CN level of 116.4 micromol/L
  • 66 fire victims who survived had mean blood CN level of 21.6 micromol/L
  • Plasma lactate level correlated more closely with blood CN level than blood CO level.
  • Elevated lactate of 10 mmol/L was sensitive (87%) for CN level > 40 micromol/L (defined level of CN toxicity) with specificity of 94% and positive predictive value of 95%.




Baud FJ et al. Elevated blood cyanide concentrations in victims of smoke inhalation. N Engl J Med 1991;325:1761-6.