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29 Cards in this Set

  • Front
  • Back
3 fluid compartments of the body
ECF (plasma & ISF)
percent of body weight equal to water
60% (TBW)
percent of TBW in ICF
percent of TBW in ECF
- plasma = 4%
- ISF = 16%
characteristics of ICF
high K, low Na & Cl (b/c pump)
little affect from change in Na
characteristics of ECF
high Na, low K
Na & water move freely
proteins do not
increase in water goes here first
changes in Na affect ECF first
changes in Na concentration affect...
ECF volume (compartment size)
concentration of Na in body
58 meq/Kg body weight
135-145 mM in ECF
normal osmolarity in body
290 mOSM
measure TBW
labeled water
long time to equilibrate
not used in clinic
measure ECF
infuse LOW CONC innulin or mannitol
(higher conc will cause vol shift)
measure plasma fluid volume
use labeled proteins
measure ICF
can't measure directly
diff between TBW & ECF
measure ISF
can't measure directly
diff between ECW & plasma volume
changes in water affect...
total body osmolarity
hyperosmotic expansion leads to
increased plasma osmolarity, plasma Na & EC volume
decreases IC volume
increase urine Na

(triggers compensatory mechs-water back in to cell)
Isoosmotic expansion leads to
expansion of ECF volume but not ICF
plasma os, plasma Na & IC volume remain the same
EC increases
increase urine Na
hypotonic expansion leads to
decreased plasma os & plasma Na
increased EC & IC
increase in urine Na

(triggers ionic mvt out of cell)
osmotic pressure
osmotic difference between compartments

depends on membrane characteristics & starling
estimate plasma osmolarity
Posm = (2xPNa) + [glucose]/18 + BUN/3

or 2xPNa
calculate dilution

sensing & response to volume changes
Baroreceptors: activate symp & RAS decrease Na excretion
increase ECFV

Osmoreceptor: activate ADH, decrease H2O out, increase ECFV w/decreased Posm

Atrial Stretch: activate ANP, increase Na out, decrease ECFV
Affect of diarrhea on body fluids
isotonic fluid loss
little effect on ICF or serum Na
Affect of sweating on body fluids
hypoosmotic water loss
like diarrhea BUT
also affects ICF & Serum Na
Affect of ADH on body fluids
hypotonic volume expansion
(opposite of diarrhea)
ICF expansion
synthesis in the kidney
1,25 Vit D
Affect of adrenal insufficiency on body fluids
loss of Na
ICF expands
TBW, ECF vol & Osm, & Serum Na decrease
factors affecting body fluid composition
Diarrhea- isotonic depletion
Sweating- hypotonic depletion
ADH- hypotonic expansion
Adrenal Insuff- Hypertonic depletion
Regulation of Extracellular fluid volume
-activate Symp & RAS
-affect Na excretion

-sense plasma osmolality
-activate ADH
-affect water excretion

Atrial stretch
-sense ECF volume
-affect Na excretion