Poisoning - Cyanides

Notes
  • Cyanide binds to cytochrome oxidase hence it inhibits cellular respiration.
  • The cause of cyanide poisoning is hydrogen cyanide and soluble cyanide salts.
  • Poorly soluble salts of cyanide have delayed toxicity manifestations and the victims should be observed for at least 24hrs.
  • The commonest causes of cyanide poisoning are domestic or industrial fires and industrial accidents. Other causes include ingestion of toxic plants, drugs such as nitroprusside sodium, terror attacks and suicidal attempts.
Symptoms
  • General weakness
  • Malaise
  • Coma
  • Dizziness
  • Seizure
  • Hypotension
  • Cardiac arrest
  • Parkinson-like syndrome (delayed reaction)
  • Neuropsychiatric condition (delayed reaction)
Management
  • Oxygenation (the key agent)
  • Activated charcoal (in case ingestion of salts within the last 4 hrs).
  • Endotracheal intubation to facilitate oxygenation
  • Hydroxocobalamin (Vit B-12) IV [ at Img/mL amp in Kenya; the main challenge being too dilute]

*It binds cyanide to form cyanocobalamin that is nontoxic.

*Dose: 70 mg/kg IV infusion over 15 mins (max. total dose 10g).

  • Sodium thiosulphate IV [neither nor in the Kenyan market]

*It increases the rate of detoxification by formation of thiocyanate after the reaction with cyanide.

*Sodium nitrite [neither nor in the Kenyan market] is added to sodium thiosulphate IV to increase its potency but care is taken to ovoid excess hypotension.

*Dose: Sodium nitrite: 300mg IV at a rate of 2.5-5 mL/min

*Sodium thiosulphate: 12.5g  IV infusion over 10 mins after sodium nitrite

  • Sodium bicarbonate in case of marked lactic acidosis.
  • Anti-convulsants:
  • *Lorazepam [neither nor in the Kenyan market] OR if not available.
  • *Midazolam at Img/mL and  5mg/mL amp in Kenya]: 10mg IM once or 0.2 mg/kg IM once [Max. dose 10mg IM] OR if not available.

*Phenobarbitone at 120mg/2mL amp in Kenya]: 1.V at rate lower than 100mg/min [max. 15mg/kg]. 1.V at rate lower than 100mg/min [max. 15mg/kg].

  1. Monitor
  • Pulse oximetry
  • Monitor cardiac and respiratory functions.
  • Serum lactate concentration
  • Re-evaluate patients 7-10 days after discharge.
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