What are the symptoms and treatment of cyanide poisoning?

From the Guidelines

Cyanide poisoning should be treated with hydroxocobalamin as the primary recommended treatment, as it does not cause hypotension or exacerbate concerns about decreased oxygen-carrying capacity. This is based on the most recent guidelines from the American Heart Association, which recommend hydroxocobalamin for cyanide poisoning 1. The treatment involves administering hydroxocobalamin (Cyanokit) at a dose of 5g IV for adults or 70mg/kg for children, which may be repeated once if needed.

Key Considerations

• Sodium nitrite is an appropriate alternative to hydroxocobalamin, particularly when carbon monoxide poisoning is not a concern 1.
• Sodium thiosulfate enhances cyanide elimination when given with hydroxocobalamin or sodium nitrite, but its mechanism of action is too slow to be considered monotherapy in life-threatening poisoning 1.
• Administering 100% oxygen is reasonable, even with a normal partial pressure of oxygen, as it can help improve cellular respiration 1.

Treatment Approach

• Call emergency services immediately if cyanide poisoning is suspected.
• Administer hydroxocobalamin or sodium nitrite as soon as possible.
• Consider adding sodium thiosulfate to the treatment regimen.
• Provide supportive care, including 100% oxygen, management of seizures with benzodiazepines, and correction of metabolic acidosis.
• Early recognition of symptoms like bitter almond breath odor, bright red venous blood, metabolic acidosis, and rapid onset of unconsciousness is crucial for successful treatment 1.

From the FDA Drug Label

If clinical suspicion of cyanide poisoning is high, administer Sodium Thiosulfate Injection without delay. Comprehensive treatment of acute cyanide intoxication requires support of vital functions. Administration of sodium nitrite and sodium thiosulfate should be considered adjunctive to appropriate supportive therapies Airway, ventilatory and circulatory support, and oxygen administration should not be delayed in order to administer sodium nitrite and sodium thiosulfate 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.

Cyanide Poisoning Treatment:

• Sodium Thiosulfate and Sodium Nitrite should be administered without delay if clinical suspicion of cyanide poisoning is high.
• Treatment decisions should be based on clinical history and signs and symptoms of cyanide intoxication.
• Supportive therapies such as airway, ventilatory, and circulatory support, and oxygen administration should not be delayed.
• Key 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 2

From the Research

Symptoms and Treatment of Cyanide Poisoning

• Cyanide poisoning causes arrest of aerobic metabolism, leading to diffuse and lethal symptoms that require high clinical suspicion 3.
• The symptoms of cyanide poisoning can be remediated with quick treatment using a cyanide antidote, such as sodium thiosulfate or hydroxocobalamin 3, 4.
• Hydroxocobalamin is an effective and safe cyanide antidote that can be administered at the scene of a cyanide disaster, and it does not need to be reserved for cases of confirmed cyanide poisoning 4.

Antidotes for Cyanide Poisoning

• There are two widely accepted antidotes for cyanide poisoning: sodium thiosulfate and hydroxocobalamin, which act on different components of cyanide's metabolism 3.
• Hydroxocobalamin can be used as a first-line antidote, and its combination with sodium thiosulfate may have a positive effect on survival without long-term neurological and visual sequelae in cases of massive cyanide poisonings 5.
• Sodium thiosulfate can also be administered in the out-of-hospital setting, but its efficacy is based on individual case studies, and there are contradictory conclusions about efficacy in animal models 6.

Administration and Efficacy of Antidotes

• Hydroxocobalamin can be administered immediately, and its effects can be potentiated or synergized by sodium thiosulfate, which has a delayed but more persistent effect 5.
• The combination of hydroxocobalamin and sodium thiosulfate can prevent death and long-term damage in patients with acute cyanide poisoning, even in aged diabetic patients 7, 5.
• The onset of antidotal action of sodium thiosulfate may be too slow for it to be the only cyanide antidote for emergency use, making hydroxocobalamin a more suitable option for out-of-hospital treatment 6.