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 standard treatment involves administering hydroxocobalamin (Cyanokit) at a dose of 5g intravenously over 15 minutes for adults, with a second dose if needed.

Some key points to consider in the treatment of cyanide poisoning include:

• Sodium nitrite is an appropriate alternative to hydroxocobalamin, particularly when carbon monoxide poisoning is not a concern, as it effectively treats cyanide poisoning 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.
• The use of 100% oxygen as therapy is reasonable, even with a normal partial pressure of oxygen, as cyanide impairs cellular respiration 1.
• Supportive care, including oxygen therapy, cardiac monitoring, and management of acidosis, is essential in the treatment of cyanide poisoning.

The American Heart Association guidelines also provide recommendations for the treatment of cyanide poisoning, including:

• Administering hydroxocobalamin for cyanide poisoning (Class I, LOE C-LD) 1.
• Administering sodium nitrite for cyanide poisoning when hydroxocobalamin is unavailable (Class I, LOE C-LD) 1.
• Administering sodium thiosulfate in addition to hydroxocobalamin or sodium nitrite for cyanide poisoning (Class IIa, LOE C-LD) 1.
• Administering 100% oxygen for cyanide poisoning (Class IIa, LOE C-EO) 1.

From the FDA Drug Label

Sodium Thiosulfate Injection is indicated for sequential use with sodium nitrite for the treatment of acute cyanide poisoning that is judged to be serious or life-threatening 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 Symptoms * 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 Treatment: The treatment for cyanide poisoning involves the sequential use of sodium nitrite and sodium thiosulfate.

• Key Considerations:
  • Treatment should not be delayed if clinical suspicion of cyanide poisoning is high.
  • Comprehensive treatment requires support of vital functions, including airway, ventilatory, and circulatory support, and oxygen administration.
  • The expert advice of a regional poison control center may be obtained by calling 1-800-222-1222.
• Administration:
  • Sodium nitrite should be administered first, followed immediately by sodium thiosulfate.
  • Blood pressure must be monitored during infusion in both adults and children.
  • The rate of infusion should be decreased if significant hypotension is noted.
• Dosing:
  • Adults:
    • Sodium Nitrite: 10 mL at the rate of 2.5 to 5 mL/minute
    • Sodium Thiosulfate: 50 mL immediately following administration of sodium nitrite
  • Children:
    • Sodium Nitrite: 0.2 mL/kg (6 mg/kg or 6-8 mL/m2 BSA) at the rate of 2.5 to 5 mL/minute, not to exceed 10 mL
    • Sodium Thiosulfate: 1 mL/kg of body weight (250 mg/kg or approximately 30-40 mL/m2 of BSA), not to exceed 50 mL total dose, immediately following administration of sodium nitrite. 2 3

From the Research

Causes and Symptoms of Cyanide Poisoning

• Cyanide poisoning can result from various exposures, including residential fires, industrial accidents, drug and plant intoxication 4
• Clinical features of cyanide poisoning include coma, respiratory arrest, and cardiovascular collapse, with lactic acidosis being a biological hallmark 4
• Symptoms of cyanide poisoning can occur rapidly, often within minutes of exposure, and may include anxiety, headache, giddiness, and mydriasis 5

Treatment of Cyanide Poisoning

• Conventional treatment of cyanide poisoning includes decontamination, supportive care, and specific antidotes 4
• Supportive care includes basic life support, such as oxygen administration and cardiopulmonary resuscitation, as well as advanced life support, including mechanical ventilation and sodium bicarbonate infusion 4
• Antidotes available for cyanide poisoning include hydroxocobalamin, sodium thiosulfate, and methemoglobin-forming agents, which work by complexing or transforming cyanide into non-toxic derivatives 4, 5
• Hydroxocobalamin is considered a safe and effective first-line antidote for cyanide poisoning, with a low risk of side effects 4, 5, 6

Combination Therapy for Cyanide Poisoning

• Combination therapy using hydroxocobalamin and sodium thiosulfate may be effective in treating massive cyanide poisonings, with potential synergistic effects between the two antidotes 6, 7
• The use of combination therapy may improve outcomes and reduce the risk of long-term neurological and visual sequelae 6
• Other combination therapies, such as hydroxycobalamin, sodium nitrite, and sodium thiosulfate, have also been reported to be effective in treating cyanide poisoning 8