From the Guidelines
Cyanide poisoning diagnosis should be based on a combination of clinical suspicion, exposure history, and symptom recognition, with immediate treatment initiation when suspicion is high, using hydroxocobalamin as the first-line treatment, as recommended by the 2023 American Heart Association guidelines 1. Diagnosing cyanide poisoning requires a high index of suspicion, particularly in patients with a history of potential exposure, such as industrial accidents, fires, or ingestion of certain substances. Key clinical signs and symptoms include:
- Altered mental status
- Metabolic acidosis
- Elevated lactate levels
- Rapid onset of symptoms like headache, confusion, seizures, and cardiovascular collapse
- Bright red venous blood due to decreased oxygen extraction
- Bitter almond odor on the breath (detectable by 60% of people)
- Cherry-red skin coloration Laboratory tests should include:
- Arterial blood gases showing metabolic acidosis with elevated anion gap
- Elevated lactate levels (often >8 mmol/L)
- Decreased central venous oxygen saturation While blood cyanide levels can confirm poisoning, results are rarely available quickly enough to guide emergency treatment. The 2023 American Heart Association guidelines recommend administering hydroxocobalamin for cyanide poisoning, with sodium nitrite as an alternative when hydroxocobalamin is unavailable 1. Additionally, it is reasonable to administer 100% oxygen for cyanide poisoning, as well as sodium thiosulfate in addition to hydroxocobalamin or sodium nitrite 1. Treatment should never be delayed for laboratory confirmation when clinical suspicion is high, as prompt intervention is critical to improving outcomes in cyanide poisoning.
From the FDA Drug Label
If clinical suspicion of cyanide poisoning is high, administer Sodium Thiosulfate Injection without delay. 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. Table 1. Common Signs and Symptoms of Cyanide Poisoning SymptomsSigns Headache Confusion Dyspnea Chest Tightness Nausea Altered Mental Status (e.g., 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
Diagnosis of Cyanide Poisoning is based on clinical history and signs and symptoms of cyanide intoxication, as there is no widely available, rapid, confirmatory cyanide blood test.
- Key signs and symptoms include:
- Altered mental status
- Mydriasis
- Plasma lactate concentration ≥ 8 mmol/L
- Tachypnea/Hyperpnea
- Hypertension/Hypotension
- Treatment decisions should be made without delay if clinical suspicion of cyanide poisoning is high 2.
From the Research
Diagnosis of Cyanide Poisoning
- Cyanide poisoning should be considered in victims of smoke inhalation from enclosed space fires and as a credible terrorism threat agent 3
- Laboratory confirmation of cyanide poisoning can take hours or days, making empiric treatment necessary 3
- Symptoms of cyanide poisoning can include cardiorespiratory arrests, deep metabolic acidosis, and coma with severe acidosis 4
Treatment of Cyanide Poisoning
- Sodium thiosulfate and hydroxocobalamin are proposed as antidotes for cyanide poisoning, with hydroxocobalamin being a potentially safer and more effective option 3, 5
- Sodium nitrite can also be used, but it may cause hypotension and methemoglobinemia, and its use should be avoided in certain situations 5
- A combination of hydroxycobalamin, sodium nitrite, and sodium thiosulfate has been shown to be effective in treating acute cyanide intoxication 6
- Sodium nitrite and sodium thiosulfate can be administered by intramuscular injection, making them more practical for out-of-hospital use 7
Important Considerations
- Prompt medical care is crucial for survival in cases of cyanide poisoning, and symptomatic treatment with sodium bicarbonate, cardiac massage, and assisted ventilation with 100% oxygen should be prioritized 4
- The efficacy of different antidotes can vary depending on the situation, and the choice of treatment should be based on the specific circumstances of the poisoning 3, 5