Case Definition: Cyanide

Clinical description

Inhalation of cyanide gas or ingestion of cyanide salts typically leads to confusion, headache, nausea/vomiting, dyspnea, tachypnea, tachycardia, and hypotension. In severe poisoning, additional signs and symptoms include bradypnea/apnea, bradycardia, seizure, coma, cardiovascular collapse, and death. Nonspecific laboratory findings include metabolic and lactic acidosis (1-3).

Laboratory criteria for diagnosis

  • Biologic: A case in which the whole blood cyanide concentration is elevated. Whole blood cyanide concentration can vary from 0.02 to 0.5 µg/mL in people without clinical manifestation of acute cyanide toxicity (3).

– OR-

  • Environmental: Detection of cyanide in environmental samples (4-7).

Case classification

  • Suspected: A case in which a potentially exposed person is being evaluated by health-care workers or public health officials for poisoning by a particular chemical agent, but no specific credible threat exists.
  • Probable: A clinically compatible case in which a high index of suspicion (credible threat or patient history regarding location and time) exists for cyanide exposure, or an epidemiologic link exists between this case and a laboratory-confirmed case.
  • Confirmed: A clinically compatible case in which laboratory tests have confirmed exposure.

The case can be confirmed if laboratory testing was not performed because either a predominant amount of clinical and nonspecific laboratory evidence of a particular chemical was present or the etiology of the agent is known with 100% certainty.

Additional resources

  1. Curry SC. Hydrogen cyanide and inorganic cyanide salts. In: Sullivan JB, Krieger GR, eds. Hazardous materials toxicology: clinical principles of environmental health. Baltimore, MD: Williams & Wilkins; 1992:698-710.
  2. Baskin SI, Brewer TG. Cyanide poisoning. In: Zajtchuk R, Bellamy RF, eds. Textbook of military medicine: medical aspects of chemical and biological warfare. Washington, DC: Office of the Surgeon General at TMM Publications, Borden Institute, Walter Reed Army Medical Center ; 1997:271-86.
  3. Kirk MA, Holstege CP, Isom GE. Nelson LS, Lewin NA, Howland MA, Hoffman RS, Goldfrank LR, Flomenbaum NE, eds. Goldfrank’s Toxicologic Emergencies. 9th ed. New York, NY: McGraw-Hill; 2011.
  4. NIOSH. NIOSH manual of analytical methods [online]. 2003. [cited 2013 Apr 5]. Available from URL:
  5. OSHA. Sampling and analytical methods [online]. 2010. [cited 2013 Apr 5]. Available from URL: icon.
  6. FDA. Food: Laboratory methods [online]. 2013. [cited 2013 Apr 5]. Available from URL: icon.
  7. EPA. Selected analytical methods: chemical methods query [online]. 2013. [cited 2013 Apr 5]. Available from URL: icon.
Page last reviewed: April 4, 2018