From the Guidelines
Cyanide poisoning is diagnosed through a combination of clinical symptoms, laboratory tests, and patient history, with treatment often initiated before laboratory confirmation due to its rapidly fatal nature. The diagnosis involves identifying characteristic signs such as rapid breathing, headache, dizziness, confusion, seizures, loss of consciousness, and a distinctive bitter almond odor on the breath, although not everyone can detect this smell 1. Laboratory confirmation is typically done by measuring blood cyanide levels, which is the most definitive test, but it is often not immediately available in emergency settings 1.
In emergency settings, physicians rely on arterial blood gas analysis showing metabolic acidosis with an elevated lactate level and an abnormally small difference between arterial and venous oxygen content, as well as elevated venous oxygen levels and an elevated anion gap, to support the diagnosis of cyanide poisoning 1. The patient's history of exposure to potential cyanide sources, such as fires involving burning plastics, industrial chemicals, certain foods like bitter almonds or cassava, or specific medications, also plays a crucial role in diagnosing cyanide poisoning 1.
Given the high morbidity and mortality associated with cyanide poisoning, initiating treatment with hydroxocobalamin or sodium nitrite, as recommended by the 2023 American Heart Association guidelines, is crucial even before laboratory confirmation 1. The administration of 100% oxygen and consideration of sodium thiosulfate as part of the treatment regimen are also supported by recent guidelines 1.
Key diagnostic features and considerations include:
- Clinical symptoms: rapid breathing, headache, dizziness, confusion, seizures, loss of consciousness
- Laboratory tests: blood cyanide levels, arterial blood gas analysis, lactate level, venous oxygen levels, anion gap
- Patient history: exposure to fires, industrial chemicals, certain foods, or specific medications
- Treatment initiation: often begins before laboratory confirmation due to the rapidly fatal nature of cyanide poisoning, with hydroxocobalamin or sodium nitrite as first-line treatments 1.
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
Cyanide poisoning is diagnosed based on clinical history and signs and symptoms of cyanide intoxication, as there is no widely available, rapid, confirmatory cyanide blood test.
- Common signs and symptoms of cyanide poisoning include:
- Headache
- Confusion
- Dyspnea
- Chest tightness
- Nausea
- Altered mental status
- Seizures or coma
- Mydriasis
- Tachypnea/hyperpnea
- Bradypnea/apnea
- Hypertension/hypotension
- Cardiovascular collapse
- Vomiting
- Plasma lactate concentration ≥ 8 mmol/L Treatment decisions should be made based on these factors, and treatment should not be delayed to obtain a plasma lactate concentration if cyanide poisoning is suspected 2.
From the Research
Diagnosis of Cyanide Poisoning
Cyanide poisoning can be diagnosed through various methods, including:
- Arterial blood gas analysis: This can help aid in the diagnosis of cyanide toxicity, as seen in a case report 3.
- Venous blood gases: An abnormally high pO2 in venous blood gases can be a clue to the diagnosis of cyanide poisoning 4.
- Electrocardiographic findings: These can range significantly, depending on the stage of the poisoning 3.
- Laboratory evaluation: This can reveal extreme anion gap metabolic acidosis, elevated lactate levels, and absent arteriovenous saturation difference 5.
- Clinical presentation: Symptoms such as seizures, apnea, and cardiovascular collapse can be indicative of cyanide poisoning 5.
Challenges in Diagnosis
Diagnosing cyanide poisoning can be challenging due to its rare occurrence and non-specific symptoms, which can mimic other disease processes 3. Additionally, anxiety and agitation are not reliable indicators of cyanide poisoning, as they can be caused by fear 6.
Importance of Prompt Diagnosis
Prompt recognition of cyanide poisoning is crucial for early intervention with antidote therapy and decreasing the extent of morbidity and mortality 5. Survival depends more on prompt medical care than on the accessibility to sophisticated antidotes 6.