Fluid compartments, Calculations, Hct, RBF, RPF

Question 1

GFR =

RPF =

RBF =

Answer 1

GFR = Cl = ((inulin urine concentration)(urine flow))/(plasma concentration of inulin))

RPF = ((Urine PAH))(Urine flow)) / (plasma PAH) Note: underestimates true RPF by about 10%

RBF = ((RPF) / (1-Hct))

Question 2

Normal HCT ( calculation and alternative calculation)

Answer 2

RBC volume / blood volume = 2.8 / 6.2 = 45% alternatively –> HCT (%) = 3X(Hb) in g/dL

Question 3

RBC volume

Answer 3

2.8L ( PART OF intracellular fluid)

Question 4

blood constist of ( and volumes )

Answer 4

RBCs (2.8L ) and plasma (3.5L) –>6.2L

Question 5

Total body water ( TBW ) - proportion

Answer 5

60% of body mass

Question 6

Non water mass ( NWM) - proportion

Answer 6

40% body mass

Question 7

total body water mass and non water mass if Body mass is 70 Kg

Answer 7

-total body water –> 60 % of body mass= 42 kg = 42 L -non water mass–> 40% of body mass = 28kg

Question 8

Total body water ( TBW) is divided to … ( and proprotions)

Answer 8

1. extracellular fluid ( ECF) –> 1/3 2. intracellular fluid ( ICF) –> 2/3

Question 9

extracellular fluid (ECF) in a body mass 70 kg

Answer 9

1/3 of 60% body mass –> 20 % of body mass–> 14 kg —> 14L

Question 10

intracellular fluid ( iCF) in body mass 70 kg

Answer 10

2/3 of 60% body mass –> 40 % of body mass –> 28kg –> 28L

Question 11

extracellular fluid ( ECF) vs intracellular fluid ( ICF) according to proportion in body mass

Answer 11

extracellular fluid ( ECF) –> 20% intracellular fluid (ICF) –> 40%

Question 12

extracellular fluid ( ECF) is divided to ( proportions and L in body mass 70 kg)

Answer 12

1. interstitial fluid –> 75% ECF –>10.5 L 2. plasma –> 25% ECF –> 3.5 kg —> 3.5 L

Question 13

Plasma volume can be measured by

Answer 13

radiolabelling albumin or Evans blue ( it binds albumin )

Question 14

Extracellular volume can be measured by

Answer 14

inulin or manitol, sulfate

Question 15

osmolarity is the

Answer 15

measure of solute concentration, defined as the number of osmoles ( Osm ) of solute per litre (L) of solution

Question 16

osmolarity - normal range

Answer 16

285-295 mOsm/ kg H2O

Question 17

Nonwater mass accounts for ____% of total body weight, or ____ kg in a person weighing 70 kg.

Answer 17

40%; 28 kg

Question 18

What fraction of total body water is extracellular vs. intracellular? What fraction of extracellular fluid is plasma vs. interstitial?

Answer 18

Total body water = one third extracellular, two thirds intracellular; of extracellular fluid = one fourth plasma, three fourths interstitial

Question 19

In an experiment, radiolabeled albumin and, later, radiolabeled inulin are infused into a patient. What two variables are being measured?

Answer 19

Radiolabeled albumin may be used to measure plasma volume, and inulin may be used to measure extracellular volume

Question 20

• What is the 60-40-20 rule of (percentage of body weight) for the average person?

Answer 20

60% of total body weight is total body water, 40% is intracellular fluid (ICF), and 20% is extracellular fluid (ECF)

Question 21

A healthy patient’s plasma osmolarity is measured during a routine visit. It is found to be normal. What value do you expect to see?

Answer 21

285–295 mOsm/kg

Question 22

• Of the extracellular fluid, what percentage is interstitial fluid, and what percentage is plasma?

Answer 22

75; 25%

Question 23

• Of the extracellular fluid in a 70-kg man, what volume and mass is the interstitial fluid, and what volume and mass is the plasma?

Answer 23

10.5 L and 10.5 kg; 3.5 L and 3.5 kg

Question 24

• What is the volume of water contained within RBCs in the intracellular fluid of a 70-kg man?

Answer 24

2.8 L

Question 25

• What is the total blood volume of an average 70-kg man? Of this volume, what percentage is hematocrit (HCT)? How is HCT calculated?

Answer 25

6 L; 45%; HCT (%) ∼ 3 × [Hb] in grams per deciliter