Cyanide Toxicity Differential Diagnoses

Updated: Sep 12, 2023
  • Author: Inna Leybell, MD; Chief Editor: Michael A Miller, MD  more...
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Diagnostic Considerations

Multiple casualties may present after a fire or hazardous materials incident involving cyanides. In some cases, the individuals involved may be experiencing collective hysteria. If physical findings are absent, cyanide poisoning is unlikely. If lactic acidosis is not present, cyanide poisoning has not occurred. Provide supportive care (oxygen) to all individuals presenting because of the event until absence of cyanide poisoning can be verified.

The following conditions can be considered in the differential diagnosis of cyanide toxicity:

  • Acute coronary syndrome
  • Anaphylaxis
  • Angina pectoris
  • Myocardial infarction
  • Apnea
  • Gastroenteritis
  • Headache
  • Meningitis and encephalitis
  • Tachycardia
  • Hemlock poisoning
  • Pulmonary embolism
  • Cardiogenic shock
  • Ischemic stroke
  • Carbon monoxide toxicity
  • Hydrogen sulfide toxicity
  • Iron toxicity
  • Isoniazid toxicity
  • Nonsteroidal anti-inflammatory drug toxicity
  • Azide toxicity
  • Methanol toxicity
  • Strychnine toxicity

Consider the diagnosis of cyanide poisoning in patients with rapid collapse or seizures accompanied by metabolic acidosis and decreased oxygen consumption. Other agents that may have similar features in toxicity include the following [10] :

  • Arsine
  • Inert gases (simple asphyxiants)
  • Metformin
  • Monomethylhydrazine
  • Organophosphorus compounds
  • Phosphine

The Chemical terrorism agents and syndromes: signs and symptoms sheet (copyright University of North Carolina at Chapel Hill) provides a comparison of presentations seen with different chemical terrorism agents at different degrees and routes of exposure.

Differential Diagnoses