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About Cyanide Poisoning

About Cyanide Poisoning

Sources of cyanide poisoning include hydrogen cyanide and its salts, cyanogenic plants, aliphatic nitriles, and prolonged exposure to sodium nitroprusside. Cyanide poisoning may result from inhalation, ingestion, or dermal exposure to various cyanide-containing compounds, including smoke from closed-space fires.1

Signs and Symptoms

Common signs and symptoms of cyanide poisoning include1:

  • Headache
  • Confusion
  • Dyspnea
  • Chest tightness
  • Nausea
  • Altered mental status (eg, confusion, disorientation)
  • Seizures or coma
  • Mydriasis
  • Tachypnea/Hyperpnea (early)
  • Bradypnea/Apnea (late)
  • Hypertension (early)/Hypotension (late)
  • Cardiovascular collapse
  • Vomiting
  • Plasma lactate concentration ≥8 mmol/L

Diagnosing cyanide poisoning may be difficult

The presence and extent of cyanide poisoning are often initially unknown. There is no widely available, rapid, confirmatory cyanide blood test. Treatment decisions must be made on the basis of clinical history and signs and symptoms of cyanide intoxication.1

Plasma lactate level could be monitored, as it increases proportionally with the degree of cyanide poisoning, but it is not a definite diagnostic tool. If cyanide poisoning is suspected, treatment should not be delayed to obtain a plasma lactate concentration.1,5,6

Where there’s smoke, there may be cyanide

Although carbon monoxide is a well-known toxin in fire smoke, cyanide can be an overlooked danger.2 Cyanide is often released when everyday items found in most homes and businesses combust, making smoke inhalation the most common cause of acute cyanide poisoning.10

With signs and symptoms similar to carbon monoxide poisoning, cyanide poisoning can be difficult to recognize. Despite the similarities, quick diagnosis is essential, and that’s often up to emergency personnel.1

Common signs and symptoms of cyanide and carbon monoxide poisoning1,17


  • • Chest tightness
  • • Hypotension
  • • Altered mental status (eg, confusion, disorientation)
  • • Mydriasis
  • • Tachypnea/Hyperpnea (early)
  • • Bradypnea/Apnea (late)
  • • Hypertension (early)/Hypotension (late)
  • • Cardiovascular collapse
  • • Plasma lactate concentration ≥8 mmol/L


  • • Headache
  • • Nausea
  • • Vomiting
  • • Confusion
  • • Dyspnea
  • • Coma
  • • Seizure


  • • Dizziness
  • • Vertigo
  • • Irritability
  • • Flu-like symptoms
  • • Fatigue
  • • Delirium
  • • Ataxia
  • • Loss of consciousness
  • • Chest pain
  • • Myocardial infarction
  • • Stroke

Recognizing cyanide poisoning in smoke inhalation victims

Cyanide poisoning should be suspected if the following manifestations are present*1,2:

  • Exposure to fire or smoke in an enclosed area
  • Soot around the mouth, nose, or back of mouth
  • Altered mental status (eg, confusion, disorientation)

*List may not be comprehensive.

Also indicative of cyanide poisoning is a plasma lactate concentration ≥10 mmol/L (a value higher than that typically listed in the table above of signs and symptoms of isolated cyanide poisoning because carbon monoxide associated with smoke inhalation also contributes to lactic acidemia).

If you suspect cyanide poisoning, administer CYANOKIT immediately.

About cyanide poisoning