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21 Cards in this Set
- Front
- Back
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Total body water distribution
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50-60% body weight
2/3 intracellular 1/3 extracellular (1/4 of which is in vasculature) |
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Volume regulation:
Sensors Effectors |
EABV sensed by baroreceptors
AII, catechols, aldosterone retain/excrete NaCl from kidneys |
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Osmolality regulation:
Sensors Effectors |
Osmolality sensed by hypothalamic osmoreceptors
ADH/AVP/vasopressin released to retain water from kidneys Thirst |
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Physical exam findings of EABV
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Orthostatic changes in pulse/BP: dec EAV
JVD, edema, ascites, pulmonary congestion: inc EAV Skin turgor, dry mucosa, sunken eyes: dec EAV |
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Lab findings of EABV
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FE Na/Cl: low = dec EAV; high = inc EAV
BUN, uric acid: inc = dec EAV (high ratio = dec EAV) |
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Effective vs. Ineffective osmols
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Effective (tonicity): Na, glucose, mannitol
Ineffective: Urea, alcohols, acetone |
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Calculating osmolality
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Plasma osm = 2 x Na + glucose/18 + BUN/2.8
Plasma tonicity = 2x Na + glucose/18 |
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ADH response to osm or EAV
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Inc osm: sensitive, linear inc ADH
Dec EAV: less sensitive inc ADH |
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ADH pathways
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Inc vascular tone (V1)
Inc H2O resorption and release vWF (V2) H2O resorption via Gs, inc cAMP, PKA, aquaporin insertion into the collecting duct |
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Pseudohyponatremia
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High triglycerides/protein levels leading to "diluted" measurement
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Primary polydipsia
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Excess H2O consumption
Urine osmolality is appropriately dilute Corrects with fluid restriction HYPOnatremia |
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SIADH
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Inc urine osmolality but normal EAV
Inappropriate ADH secretion by the CNS HYPOnatremia |
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Volume depletion
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Diarrhea, diuretics
Inc urine osm, low EAV and low extracellular fluid volume HYPOnatremia |
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Edematous disorders
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CHF, cirrhosis, nephrosis
Inc urine osm, low EAV, normal extracellular fluid volume HYPOnatremia |
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Hypertonicity with dec volume
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Renal loss (osmotic diuresis, diuretics)
Extrarenal loss (resp, skin, GI) |
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Central DI
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CNS ADH secretion is inhibited (trauma, tumors, infection, genetic)
Corrects with ADH administration but not with fluid restriction |
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Nephrotic DI
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ADH resistance
Urinary obstruction, kypokalemia, hypercalcemia, amyloidosis, sickle cell disease, PCKD, drugs, genetic Does not respond to ADH or fluid restriction |
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Hypertonicity with inc volume
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Iatrogenic administration of hypertonic solutions
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Effects and treatment of HYPOnatremia
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Acute: cerebral edema
Chronic: cells dec osm to accommodate for dec osm of plasma Correct slowly (0.5 mEq/L/hr) to avoid central pontine myelinolysis |
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Effects of HYPERnatremia
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Acute: cells shrink
Chronic: cells import/synthesize solutes to inc osm Correct slowly to avoid cerebral edema (correct volume depletion first if present) |
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Approach to polyuria/polydipsia
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U osm: inc = osmotic diuresis; dilute - fluid deprivation
Fluid dep: inc U osm = primary polydipsia; dilute - ADH admin ADH: inc U osm = central DI; dilute = nephrogenic DI |
