Sodium and water homeostasis Flashcards
what are the determinants of sodium reabsorption at the PCT?
- Na-H exchange
- Na-glucose cotransport
- AT II
- NE
- peritubular capillary hemodynamics
how much sodium is reabsorbed at the loop of henle? what determines the reabsorption?
- 25-30%
- flow dependent
what are the clinical signs of volume (sodium) expansion?
- edema
- pulmonary crackles
- ascites
- JVD
- hepatojugular reflux
- HTN
what are the diuretic therapies for volume expansion?
- carbonic anhydrase
- loop
- thiazide
what is the normal physiologic serum osmolality?
285 - 290 mOsm/kg
what is responsible for the generation of medullary hypertonicity?
- thick ascending limb of loop of henle - actively transports NaCl leading to tubular dilution and increased concentration of urea
- late distal tubule - water moves from hypotonic fluid to interstitium under influence of ADH
what are the intrarenal factors that can cause hyponatremia?
- diminished delivery of fluid to diluting segments of nephron
- defect in NaCl transport out of the water-impermeable segments of the nephron
- continued secretion of ADH
what are the features of SIADH?
- decreased ECF effective osmolarity
- inappropriate urinary concentration
- clinical euvolemia
- elevated urinary sodium concentration with normal salt and water intake
what are the treatment options for chronic hyponatremia?
- fluid restriction
- inhibition of ADH action
- increased solute intake
what is the first line of defense against water depletion and hyponatremia?
renal concentrating mechanism
what test is used to differentiate central vs nephrogenic DI?
water deprivation test
what is the treatment for complete central DI?
ddAVP
what is the treatment for partial central DI?
- vasopressin
- chlorpropramide
- clofibrate
- carbamazepine
what is the treatment for nephrogenic DI?
- correct calcium and potassium
- remove offending drugs
- low sodium diet
- thiazide diuretic
- amiloride
