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26 Cards in this Set
- Front
- Back
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Does PaO2 refer to alveolar or arterial pressure?
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arterial
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Which binds O2, Fe+2 or Fe+3?
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Fe+2
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Cyanosis occurs when:
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SaO2 < 80%
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Methemoglobinemia: Definition, symptoms and treatment
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Fe+3 bound to heme
chocolate-colored blood, cyanosis Methylene blue (activates metHb reductase) and ascorbic acid (reduces Fe+3 to Fe+2) |
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Hypoxia or hypoxemia: low blood PO2
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hypoxemia
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Mechanism of adaptation to high altitude
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Hypoxemia --> peripheral chemoreceptors --> hyperventilation --> respiratory alkalosis --> alkalosis activates PFK --> increased 1,3-BPG --> 2,3-BPG --> right shift O2 curve
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Define: ischemia
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decreased arterial or venous blood flow
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Four causes of hypoxemia
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1. Respiratory acidosis (˄ PACO2 --> ˅ PaO2)
2. Ventilation defects (intrapulmonary shunt, 100% O2 does nothing) 3. Perfusion defects (dead space, 100% O2 ˄PaO2) 4. Diffusion defects |
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3 causes of respiratory acidosis
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depression of medullary respiratory center (barbiturates), paralysis of diaphragm, chronic bronchitis
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Example of ventilation defect
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Respiratory distress syndrome with collapse of the distal airways
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Example of perfusion defect
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Pulmonary embolus
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2 examples of diffusion defects
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interstitial fibrosis
pulmonary edema |
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Anemia - Definition, 4 causes
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˅[Hb] (~PaO2, ~SaO2)
˅Hb production (Fe def) ˄RBC destruction (hereditary spherocytosis) ˅RBC production (aplastic anemia) ˄RBC sequesteration (splenomegaly) |
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Methemoglobinemia - definition, 2 causes, treatment
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metHb is Hb bound to Fe+3 (can't bind O2). ~PaO2, ˅SaO2
1. oxidizing agents (nitro and sulfa drugs, eg nitroglycerin) 2. deficiency in metHb reductase (converts Fe3 to Fe2) methylene blue (activates metHb reductase) ascorbic acid (reduces Fe+3) |
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CO poisoning: symptoms, pathogenesis
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Headache (first symptom), Cherry-red discoloration of skin and blood, coma, necrosis of GP
- CO competes for binding sites on Hb --> ˅SaO2, ~PaO2, left shift OBC (since more cooperativity) - Also inhibits cytochrome oxidase in ETC |
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What can left shift OBC?
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˅2,3-BPG (glycolytic intermediate)
CO alkalosis metHb (Fe+3) fetal Hb hypothermia |
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CN poisoning: causes, pathogenesis, treatment
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drugs (eg nitroprusside), combustion of polyurethane
CN inhibits cytochrome oxidase in ETC amyl nitrite (makes metHb which binds CN) then thiosulfate (CN --> thiocyanate) |
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Uncoupling proteins
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thermogenin (brown fat in newborns), dinitrophenol (used in making TNT)
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2 agents that damage inner mitochondrial membrane
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alcohol, salicylate
leads to hyperthermia |
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subendocardial ischemia: causes, symptoms
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coronary artery atherosclerosis
increased myocardial O2 demand (exercise) with concurrent LV hypertrophy angina (chest pain), ST segment depression |
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Watershed area between blood supplies: define, 2 examples
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where blood supply from two vessels do not overlap
- between anterior and middle cerebral arteries - splenic flexure (between SMA and IMA) |
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areas prone to hypoxia
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watershed areas between blood supplies
subendocardial tissue (receives the least amount of O2 from coronary arteries) renal cortex: straight part of PT renal medulla: TAL |
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Reversible changes in hypoxic cell injury
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˅ATP synthesis
˄anaerobic glycolysis (low citrate + high AMP --> activation of PFK) impaired Na,K pump --> Na entry --> cellular swelling detachment of ribosomes --> ˅protein synthesis |
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Irreversible changes in hypoxic cell injury
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˅ATP --> ˅Ca-ATPase --> ˄[Ca] --> two things:
-enzyme activation ˄phospholipase --> ˄membrane permeability proteases --> damage cytoskeleton endonucleases --> karyolysis (fading of nuclear chromatin) -Ca enters mitochondria --> ˄mitochondrial membrane permeability --> release cyt c --> apoptosis |
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Damage caused by free radicals
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DNA fragmentation and dissolution
(Polyunsaturated) Lipid peroxidation in membranes |
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Sources of free radicals
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O2 (superoxide, hydroxyl, peroxides)
drugs (from liver cytochrome P-450. eg acetaminophen, CCl4) |
