1. Cell Injury Flashcards
What do we use to measure oxygen in the body?
Hemoglobin, oxygen saturation (on the heme), partial pressure of arterial oxygen
What does it mean for oxygen saturation to be 100%?
All 4 spots on heme bound to oxygen
What is partial pressure of arterial oxygen?
Oxygen dissolved in PLASMA
What is the relationship between oxygen saturation and partial pressure of arterial oxygen?
Move in the SAME direction because oxygen saturation gets its oxygen from the oxygen dissolved in plasma
What is the most common cause of ischemia?
Thrombus in muscular artery
What is hypoxemia?
Decreased partial pressure of arterial oxygen
Whenever you have respiratory acidosis, what happens to partial pressure of O2?
Goes down - hypoxemia; there is always an inverse relationship between PCO2 and PO2
Patient with hypoxemia given 100% O2 and O2 doesn’t increase - what’s happening?
Shunt - perfusion but no ventilation (kids - hyaline membrane disease, adults - adult respiratory syndrome)
What happens when you give 100% O2 to someone with a perfusion defect?
O2 will increase because not every single alveoli is not perfused
Does anemia give you hypoxemia?
NO - it gives you decreased Hgb but PO2 and oxygen saturation are normal
You will have hypoxia (tissue lacks oxygen) but not hypoxemia (PO2 in the blood is normal)
Heater in the winter time, automobile exhaust, house fire - what should you think of?
CO poisoning
What else should you think of with house fire aside from CO poisoning?
Cyanide poisoning because of upholstery on furniture
What is the only lab value affected in CO poisoning?
Oxygen saturation is decreased because CO displaces O2 on the heme
How do we treat CO poisoning?
100% oxygen
What does cyanosis mean?
Decreased oxygen saturation
What is the first symptom of CO poisoning?
Headache
Why do we not see signs of cyanosis with CO poisoning?
It produces a cherry red pigment that can mask the blue
What is methemoglobin?
Hemoglobin with FE3+ instead of 2+ which makes it so that oxygen can’t bind - decreased oxygen saturation
Dude coming out of the Rocky Mountains, cyanotic, give him 100% O2 and he’s still cyanotic - diagnosis?
Methemoglobinemia because of drinking water with nitrites/nitrates which are oxidative agents
What is the main treatment for methemoglobinemia?
Methylene blue
What are 2 things that sulfa and nitro drugs (oxidizing agents) do?
- Produce methemoglobin
2. Produce hemolytic anemia in G6PD deficiency
Why do we see methemoglobinemia in HIV patients?
They are usually on TMP-SMX for treatment of PCP
What shifts hemoglobin curve to the right?
CADET: CO2, acidosis, 23BPG, Elevation (causes increase in synthesis of 23BPG), Temperature
What shifts hemoglobin curve to the left?
CO, HbF, alkalosis
What inhibits cytochrome oxidase?
CO and cyanide (think 3 C’s)
What does CO do?
- decreases O2 sat
- shifts hemoglobin curve to the left
- inhibits cytochrome oxidase
this is why CO is so bad
What is one of the complications of salicylate poisoning?
Hyperthermia because salicylates are uncoupling agents
Acute respiratory acidosis - what happens to Hgb, oxygen sat, PO2?
Hgb - nothing, Oxygen sat and PO2 - both decreased
What can you give in addition to methylene blue for methemoglobinemia?
Ascorbic acid
What are the biggest problems in tissue hypoxia?
- Decrease in ATP leading to anaerobic glycolysis and lactic acid build up
- ATPase pumps broken
3.
What does the build up of lactic acid do in a cell?
Denature proteins and enzymes –> coagulation necrosis (grossly: infarction)
Why are cells swollen in tissue hypoxia?
Decreased ATP –> Na-K pump stops working –> Na stuck in cell –> cell swells
What happens to calcium in tissue hypoxia?
Enters cell because Ca-ATPase pump stops working - once it’s in the cell calcium activates all kinds of enzymes (membrane damage, nuclear pyknosis)
When you have free radical damage what kind of pigment do you see in cells?
Lipofuchsin - can’t break down lipids all the way
What is the most common cancer that comes from radiation?
Leukemia
