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Thursday, March 22, 2007

Cyanide Toxicity

  • Causes
    • Infusion with Nitroprusside
    • Smoke Inhalation (MCC)
      • Combustion of polyurathane (found in mattresses – just look at the tag)
  • Effects
    • Inhibits cytochrome oxidase (cytochrome a/a3) of the electron transport chain
      • NOT cytochrome C (commonly mistaken)
      • Blocks the use of oxygen → tissue hypoxia and rapid death
  • Si/Sx
  • Treatment
    • Amyl and Sodium Nitrite
      • Produces methemoglobin (met-HB)
        • note: nitrates used for anginal therapy do not cause formation of cy
      • Met-HB sucks up CN from the mitochondria
        • Iron in met-HB (Fe3+) has stronger affinity for CN than does cytochrome oxidase’s iron
      • Results in formation of cyanomethemoglobin
    • Sodium Thiosulfate
      • Converts cyanomethemoglobin into:
        • Thiocyanate
          • less toxic & easier to excrete than cyanomethemoglobin
        • Methemoglobin
          • Methemoglobinemia is treated with methylene blue

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