Question: The diagnosis of cyanide toxicity is generally a clinical one as blood cyanide levels are rarely if ever available quickly. Which readily available laboratory test may be helpful in the diagnosis cyanide toxicity in victims of smoke inhalation specifically?
Answer: The cited article notes: “Although blood cyanide concentration can be measured, it is not of use for diagnosis in the acute setting as few laboratories perform the assay and results cannot be obtained rapidly. Diagnosis is therefore clinical; however, plasma lactate has been found to correlate with the severity of cyanide toxicity due to lactic acidosis from the prevailing anaerobic metabolism. In victims of smoke inhalation with burns <15% total body surface area (TBSA), a plasma lactate level >10 mmol/L (90 mg/dL) has been found to be a sensitive indicator of cyanide toxicity suggesting blood cyanide levels >40 mmol/L (1.0 mg/L).” (MacLennan L and Moieman N. Management of cyanide toxicity in patients with burns. 2015 Burns 41:18-24)