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22 Cards in this Set
- Front
- Back
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What does the osmolarity of ECF and ISF compare at steady state?
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They are equal - isotonic
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How is the equality of osmolarity in ECF/ISF achieved?
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By shifting of water between the compartments, but no shifting os solutes (NaCl and mannitol)
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What is a key example of isosmotic volume expansion?
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Infusion of isotonic NaCl solution
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How does infusion of isotonic NaCl solution affect
-ECF vol -ICF vol -ECF osmolarity -Hct/Serum [Na] |
ECF vol - increases
ICF vol - no change ECF osmolarity - no change Hct - decreases Na conc - no change |
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What is a key example of Isosmotic volume Contraction?
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Diarrhea
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How does diarrhea affect
-ECF vol -ICF vol -ECF osmolarity -Hct/Serum [Na] |
ECF - decreases
ICF - no change ECF osmolarity - no change Hct - increases Na conc - no change |
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So the only 2 parameters affected by adding or removing ISOSMOTIC fluid are:
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-ECF volume
-Hematocrit |
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What is a key example of HYPERosmotic volume EXPANSION?
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High salt NaCl intake
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How does High NaCl intake affect
-ECF vol -ICF vol -ECF osmolarity -Hct/Serum [Na] |
ECF vol - increases
ICF vol - decreases ECF osm - increases Hct - decreases Na conc - increases |
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What are 3 examples of Hyperosmotic volume CONTRACTION?
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-Sweating
-Fever -Diabetes insipidus (lost in a desert - loss of water) |
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How does sweating/fever/Diab insipidus affect
-ECF vol -ICF vol -ECF osmolarity -Hct/Serum [Na] |
ECF vol - decreases
ICF vol - decreases ECF osm - increases Hct - no change Na conc - increases |
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Why doesn't water loss and hyperosmotic volume contraction affect the hematocrit?
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Because though the ECF volume is depleted, water has shifted from the RBCs to the ECF; the vol decrease offsets the concentrating effect of low ECF.
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What is a key example of Hyposmotic volume Expansion?
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siADH (anti-diuresis means retention of water)
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How does SIADH affect
-ECF vol -ICF vol -ECF osmolarity -Hct/Serum [Na] |
ECF vol - increases
ICF vol - increases ECF osm - decreases Hct - no change Na conc - decreases |
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Why is hematocrit unchanged in SIADH?
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Again because water shifts INTO RBC's, so even though they are diluted, their higher volume keeps the Hct normal.
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What is hematocrit?
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A measure of RBC VOLUME - not number of cells or just concentration within plasma.
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What is a key example of HYPOSMOTIC volume CONTRACTION?
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Adrenal insufficiency (not enough aldosterone)
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What is the result of low aldosterone?
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Not enough salt retention - the kidneys excrete more NaCl than water.
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So how does Adrenal insufficiency affect
-ECF vol -ICF vol -ECF osmolarity -Hct/Serum [Na] |
ECF vol - decreases
ICF vol - increases ECF osm - decreases Hct - increases Na conc - decreases |
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How does adrenal insufficiency affect blood pressure?
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It decreases
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What other fluid shift will lower blood pressure?
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Diarrhea
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What fluid shift will INCREASE blood pressure?
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Infusion of isotonic saline (isosmotic volume expansion)
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