Body Fluid Compartments - McCormick Flashcards
Total body water
0.6 x body weight
2/3 is ICF
1/3 is ECF
ECF
0.2 x body weight 2 compartments 1. Interstitial - 3/4 2. Plasma - 1/4 --> 80% is venous (2.8L) --> 20% is arterial (.7L)
Third space
Pathological third space in the ECF
ex. synovial, CSF, etc
Effects of hypovolemia on ECV ECF volume Plasma volume Cardiac output
D ECV
D ECF volume
D plasma volume
D cardiac output
Effects of heart failure on ECV ECF volume Plasma volume Cardiac output
D ECV
I ECF volume
I plasma volume
D cardiac output
Volume of distribution
Of a drug - pharmacology - important for loading doses
Vd < 3L in plasma only
Vd = 14L in drug and ECF
Vd = 40-45L drug occupies TBW
Vd > 45L distributed and bound in body tissues
Oncotic pressure
Generated by large proteins in solution that are impermeable
How to calculate total blood volume (TBV)?
Plasma volume / 1 - hematocrit
If you have TBW and ECF, how do you calculate ICF?
TBW - ECF
ICF + ECF = total body water
2 ways to estimate plasma osmolality?
[Na+] x 2
OR
[Na+] x 2 + glucose/18 + urea/2.8
Donnan effect
Negative charge of proteins within vasculature attracts positively charged Na and K ions
What establishes osmolarity in the ECF?
The presence of Na + Cl
-water follows Na
What establishes osmolarity in the ICF?
K+
Where does water and solutes go first?
The ECF
Why you look at the ECF first
Water moves between the two when an osmotic pressure gradient exists
Fluid distribution between plasma and interstitial fluid is maintained by?
Balance of hydrostatic and osmotic forces across capillaries
