Dyshemoglobinemias Flashcards
What two components make up heme?
Iron + porphyrin
Ferrous state (Fe2+) carries O2
What is the only instance when the body’s CO levels will rise after removal from the source of carbon monoxide and how does this happen?
Methylene chloride is converted to CO in vivo
Why is CO so dangerous? Give 3 reasons
CO binds to Hgb with 200x’s the affinity of oxygen, which blocks O2 from binding. Also, CO binds to mitochondrial cytochrome oxidase and inhibits the ETC. CO also displces NO from platelets, which forms free radicals that can damage the CNS.
Your patient comes to the ED after being in a house fire. She is experiencing chest pain, blurred vision, dyspnea on exertion, tachycardia, tachypnea, and ataxia. What level of CO has she been exposed to? How would you treat? What would her Pulse Ox and ABG levels look like?
She has been exposed to a moderate amount of CO, and would treat with oxygen to enhance the clearance of CO. Her pulse ox would be falsely normal and her ABG co oximeter would be correct but the calculation would be falsely normal.
Describe the late effects of CO toxicity and the theory behind it. What attempts are made to prevent this?
Cognitive decline, movement disorders, and neuropathy due to reperfusion injury and free radical formation. Prevent with hyperbaric oxygen.
What are the indications for use of hyperbaric oxygen?
loss of consciousness, GCS < 15, CO level > 10%, and neurological signs
How does cyanide interfere with body’s function? (Why is it so good at being really really bad for us?)
Cyanide binds to cytochrome A3 on the ETC, which rapidly leads to multi-system organ failure since there is no ATP being made
James Bond has been captured! The Russians tried to get 007 to talk and threatened him with a cyanide pill. James took it like a champ, then used their distraction to escape and ran straight to you because he knows you can fix him up quickly. What did you give England’s favorite spy to counteract the cyanide and how does it work?
Give him hydroxycoblamin (vitamin B12a) because it binds with the cyanide to make cyanocobalamin (B12).
What can sodium thiosulfate be used for and how does it work?
Cyanide exposure; works by enhancing the normal metabolism of cyanide through the rhodanase enzyme
What is a good way to attract cyanide from the Fe3+ of the cytochromes to the Fe3+ in the Hgb and when should you absolutely not apply this approach?
Use nitrites, except for in concurrent CO poisoning (i.e. smoke inhalation)
What common drugs can cause the amount of methemoglobin in the blood to increase?
nitrites, local anesthetics
What is methylene blue used for and how does it work?
Used to treat methemoglobinemia, works by using NADPH as a cofactor to reduce methemoglobin to hemoglobin
At what levels of metHgb would you consider administering methylene blue and what patients is methylene blue ineffective for?
Use when metHgb >20-30% or the patient is experiencing symptoms. CANNOT use with patients that have G6PD deficiency.
