cyanide toxicity

• causes
• infusion with nitroprusside
• smoke inhalation (MCC)
• 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 death
• signs & symptoms
• bitter almond-scented breath
• agonal respiration (seen at cerebral ischemia, hypoxia or anoxia = shallow, slow irregular breathing accompanied by irregular pauses)
• nausea and headache
• treatment
• amyl and sodium nitrite
• produces methemoglobin (metHb)
• metHb sucks up cyanide from the mitochondria
• iron in metHb (Fe3+) has stronger affinity for cyanide than 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