From the Guidelines
Cyanide poisoning presents with a combination of neurological, cardiovascular, and metabolic manifestations, and immediate treatment with hydroxocobalamin is crucial to prevent mortality and morbidity. Patients typically exhibit altered mental status ranging from confusion to coma, seizures, and respiratory depression. Cardiovascular signs include tachycardia initially, followed by bradycardia, hypotension, and eventually cardiovascular collapse. A key finding is the presence of bright red venous blood due to the inability of tissues to extract oxygen. Patients often have a bitter almond odor on their breath, though not everyone can detect this smell. Metabolic acidosis with an elevated anion gap and elevated lactate levels are characteristic laboratory findings, as noted in the 2020 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care 1.
The symptoms of cyanide poisoning develop rapidly after exposure, with death potentially occurring within minutes to hours without treatment. The toxicity of cyanide is predominantly due to the cessation of aerobic cell metabolism, as it reversibly binds to the ferric ion cytochrome oxidase in the mitochondria and stops cellular respiration and adenosine triphosphate production 1. Treatment involves administering hydroxocobalamin (Cyanokit) 5g IV over 15 minutes, which can be repeated once if needed, as it has a better safety profile compared to nitrites. Sodium thiosulfate (12.5g IV) can be given as an adjunct therapy to enhance the effectiveness of nitrites, although its role in patients treated with hydroxocobalamin is less certain 1.
Some key points to consider in the management of cyanide poisoning include:
- Immediate administration of hydroxocobalamin
- Supportive care including oxygen, ventilatory support, and management of seizures and hypotension
- Handling of the victim's clothes and body fluids with care, especially in cases of corrosive chemicals or substances that are easily absorbed through the skin or respiratory tract, as noted in the 1998 European Resuscitation Council guidelines for adult single rescuer basic life support 1
- The importance of prompt treatment to prevent life-threatening arrhythmias and neurological sequelae.
The most critical aspect of managing cyanide poisoning is prompt recognition and treatment, as delayed therapy can lead to increased morbidity and mortality. Therefore, it is essential to be aware of the signs and symptoms of cyanide poisoning and to have a plan in place for immediate treatment.
From the FDA Drug Label
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
The presentation of cyanide poisoning includes headache, confusion, dyspnea, chest tightness, nausea, altered mental status, seizures or coma, mydriasis, tachypnea/hyperpnea, bradypnea/apnea, hypertension/hypotension, cardiovascular collapse, and vomiting. Key indicators also include a plasma lactate concentration ≥ 8 mmol/L 2.
- Altered mental status and mydriasis are suggestive of true cyanide poisoning.
- Hypotension is highly suggestive of cyanide poisoning, but only present in a small percentage of cases.
- A plasma lactate concentration ≥ 10 mmol/L is also indicative of cyanide poisoning in smoke inhalation victims 2.
From the Research
Presentation of Cyanide Poisoning
The presentation of cyanide poisoning can be diffuse and lethal, requiring high clinical suspicion for diagnosis 3. The symptoms of cyanide poisoning include:
- Diffuse and lethal symptoms
- Arrest of aerobic metabolism
- Severe metabolic acidosis
- Coma with severe acidosis
- Cardiorespiratory arrests
- Deep metabolic acidosis
- Profound anion gap metabolic acidosis secondary to elevated lactate levels
Diagnosis and Treatment
Cyanide poisoning must be seriously considered in victims of smoke inhalation from enclosed space fires, and it is also a credible terrorism threat agent 4. The treatment of cyanide poisoning is empiric because laboratory confirmation can take hours or days. The available antidotes for cyanide poisoning include:
- Sodium thiosulfate
- Hydroxocobalamin These treatments act on different components of cyanide's metabolism 3. Hydroxocobalamin seems to be an appropriate antidote for empiric treatment of smoke inhalation and other suspected cyanide poisoning victims in the out-of-hospital setting 4.
Case Studies
Several case studies have reported the use of antidotes in the treatment of cyanide poisoning. For example, a combination of hydroxycobalamin, sodium nitrite, and sodium thiosulfate was used to treat a patient with acute cyanide intoxication, resulting in complete recovery in 48 hours 5. Another case study reported the use of antidote therapy in a teenager with cyanide poisoning, but the patient never recovered neurologic function and was declared brain dead 6.
Symptomatic Treatment
Symptomatic treatment is also important in the management of cyanide poisoning. This includes:
- Sodium bicarbonate
- Cardiac massage
- Assisted ventilation with 100% oxygen
- Supportive therapy Prompt recognition of the possibility of cyanide poisoning and early intervention with antidote therapy and symptomatic treatment can decrease the extent of morbidity and mortality 7.