Distribution And Measure Of Fluid Volumes

Question 1

ICF Volume is controlled by

Answer 1

ECF osmolarity not ECF volume

Question 2

Major principles

Answer 2

Cellular function influenced by changes of ECF
Most commonly measure ECF and ICF based on changes in ECF
Plasm is ECF (including glucose, hyperkalemia, serum)
Solute and fluids are gained and lost by passing through ECF

Question 3

Normal volumes of fluid compartments

Answer 3

Water is 60% of mass
⅔ of TBW is ICF (.4 x wt)
⅓ of TBW is ECF (.2 x wt)

Question 4

Effective osmolarity

Answer 4

Osmolarity = concentration of all solute particles in a solution

Effective osmolarity is under valued, evaluates on one solute

Question 5

Blood volumes

Answer 5

Blood volume averages 8%
Plasma is ECF
Rbc and wbc is ICF
Primarily it is interstitial fluid that bathes the cells
Most of ECF is in the tissues

Question 6

Measurement of fluid volumes

Answer 6

V = MC

VOD = (amount injected - amount removed from the body)/ concentration in the sample

Question 7

Measurement of ECFV

Answer 7

Measure ECFV need a substance that freely diffuses from the plasma into which it was injected into the interstitial fluid but is not taken up by the cells

Sodium Space
Sucrose: normally not present in blood but significantly metabolized
Inulin: not taken up by cells or metabolized but excreted into urine
Mannitol

Question 8

Measurement of total body water

Answer 8

Need a substrate that rapidly distributes throughout both extra cellular and intracellular space but also distributes passively and not accumulate in one of the other

Deuterated H2O
Antipyrine

Question 9

Measurement of ICF

Answer 9

ICFV = TBW - ECFV

Question 10

Plasma volume measurement

Answer 10

Remain with the ECF component of the blood that will not be taken up by rbc and will not leave blood vessels and become diluted in interstitial fluid

RISA
Evans blue dye

Question 11

Estimation of fluid volumes

Answer 11

1. At equilibrium, osmolarity in ECF and ICF are equal
2. When you add a fluid , you add it to the total fluids, but solute is added only to ECF
3. Water will distribute to equalize the osmolarities in the compartments

Question 12

How solve fluid distribution problems

Answer 12

1. List initial conditions
2. Add the volume of additional water to the total fluids
3. Add new solutes to total solutes
4. Calculate the total body osmolarity and record this in all compartments
5. Add the solutes to the ECF compartment
6. Using new osmolarity and new extra cellular solutes, calculate ECFV
7. Subtract ECF volume from the total volume to get ICFV