Fluid Balance Flashcards
filtration
liquids moved by pressure (ex: COP, hydrostatic pressure)
normal serum osmolarity
275-295 mOsm/kg
hyperosmolarity
> 295 mOsm/kg
hypoosmolarity
<275 mOsm/kg
osmolarity affects
tonicity
osmotic pressure
pressure needed to prevent osmosis through a semipermeable membrane
-proportional to the osmolarity of a solution
hypotonic solutions
lower osmotic pressure than blood-fluid goes into the ICF and causes cell swelling
-1/2 normal saline
-2.5 dextrose
hypertonic solutions
higher osmotic pressure than blood-fluid goes into the ECF and causes cell shrinkage
-5% dextrose normal saline
-5% dextrose lactated ringer
fluid is balanced through:
thirst, RAAS, ADH, ANP
renin-angiotensin-aldosterone system (RAAS)
decreased perfusion to kidneys>kidneys release renin>renin and angiotensinogen makes angiotensin I>in lungs becomes angiotensin II>angiotensin II makes adrenal cortex (kidney) release aldosterone>aldosterone tells kidney to reabsorb Na+ and excrete K+>water follows Na+ into ECF
hyperaldosteronism causes:
too much water because of an excessive amount of Na+
antidiuretic hormone (ADH)
secreted by posterior pituitary from increased osmolarity in blood
-increases water retention/ECF water volume
atrial natriuretic peptide (ANP)
released by atria, decreases water retention
-inhibits renin secretion
-blocks secretion/action of aldosterone (less Na+ absorption, less water)
total gains/losses of fluid in body
2500mL in, 2500mL out
hypovolemia causes
excessive fluid losses
-ex: GI losses, hemorrhage, excessive NG suctioning,
inadequate fluid intake
-ex: dysphagia, unconsciousness, reduced thirst sensation, lack of fluids with tube feedings
third-spacing
ex: burns, intestinal obstruction, edema, ascites