1. Body fluids compositions, and their measurements
By: DR QAZI IMTIAZ RASOOL

2. OBJECTIVES
a)Discuss the distribution of total body H2O (TWB) in the body
b) List the ionic composition of different body compartments
c) Explain the principles of measurements

3. Body as an open sytem Body exchanges materials and energy with its surroundings

4. Regulatory influences
Route
Range (l/day)
Regulatory influences
Insensible - lungs
Atmospheric vapor pressure (temperature)
Insensible - skin
10x increase in burn victims
Sweat
0.1-2 (per hour)
Temperature, exercise
Feces
Diarrheal disease
Urine
Body fluid composition

5. FACTORS AFFECTING Total Body H2O varies depending on body fat:
Infant: 73-80%
Male adult: 60%
Female adult: 40-50%
Effects of obesity
Old age 45%
Climate Level of physical activity

6. PERCENTAGE OF H2O IN TISSUES

7. PLASMA INTERSTITIAL TRANSCELLULAR
FLUID COMPARTMENTS
EXTRA CELLUAR INTRA CELLULAR
FLUID (cytosol)FLUID
PLASMA INTERSTITIAL TRANSCELLULAR
FLUID FLUID
CSF
Intra ocular
Pleural
Peritoneal
Synovial
Digestive Secretions

8. % is important in fluid therapy
PERCENTAGE OF WATER IN TISSUES
Average 70 kg person total body weight
42 litres total H2O %
28 l. Intracellular fluid (ICF) %
14 l. Extracellular fluid (ECF) %
% is important in fluid therapy
divided into ¾ ISF and ¼ plasma water
10.5 l. Interstitial fluid (ISF) %
3.5 l. Plasma water %

9. Regulation of H2O Intake
The hypothalamic thirst center is stimulated:
By a decline in plasma volume of 10%–15%
By increases in plasma osmolality of 1–2%
Via baroreceptor input, angiotensin II, and other stimuli

11. Net Osmotic Force Development
Semipermeable membrane
Movement some solute obstructed
H2O (solvent) crosses freely
End point:
H2O moves until solute concentration on both sides of the membrane is equal
OR, an opposing force prevents further movement
H2O 34 34

12. Solutes – dissolved particles
Electrolytes – charged particles
Cations – positively charged ions
Na+, K+ , Ca++, H+
Anions – negatively charged ions
Cl-, HCO3- , PO43-
Non-electrolytes - Uncharged
Proteins, urea, glucose, O2, CO2

13. APPROXIMATE IONIC COMPOSITION OF THE
BODY H2O COMPARTMENTS

14. Summary of Ionic composition
Interstitial
H2O
Plasma
H2O
Cell
H2O 32 32

15. Intra-ECF H2O Redistribution Plasma vs. Interstitium
Balance of Starling Forces acting across the capillary membrane
osmotic forces
hydrostatic forces
Plasma vs Interstitial Space
-Balance between Hydrostatic and Colloid Osmotic forces across the capillary membranes
Intracellular vs Extracellular
Osmotic effect (e.g. electrolytes)
ICFV is NOT altered by: iso-osmotic changes in extracellular fluid volume. 50 50

16. Plasma Osmolarity Measures ECF Osmolarity
Plasma is clinically accessible
Dominated by [Na+] and the associated anions
Under normal conditions, ECF osmolarity can be roughly estimated as: POSM = 2 [Na+]p mOSM 54 54

17. Net Osmotic Force Development
Ionic composition very different
-Total ionic concentration very similar
-Total osmotic concentrations virtually identical
Semipermeable membrane.
Movement some solute obstructed.
H2O (solvent) crosses freely.
End point:
H2O moves until solute concentration on both sides of the membrane is equal.
OR, an opposing force prevents further movement. 34 34

18. Disorders of H2O Balance: Dehydration
Cells lose H2O to ECF by osmosis; cells shrink 1
Excessive loss of H2O from ECF 2
ECF osmotic pressure rises 3
(a) Mechanism of dehydration

19. Primary Disturbance: H2O moves out of cells
ECF Osmolarity ?
ECF Osmolarity ?
H2O moves out of cells
ICF Volume decreases (Cells shrink)
ICF Osmolarity increases
Total body osmolarity remains higher than normal
H2O moves into the cells
ICF Volume increases (Cells swell)
ICF Osmolarity decreases
Total body osmolarity remains lower than normal 52 52

20. CRITERIA FOR A SUITABEL DYE.
BODY FLUID MARKER
Must mix evenly throughout the compartment
Non toxic, no physiological activity
Even mixing
Must have no effect of its own on the distribution of H2O or other substances in the body
Either it must be unchanged during the experiment or if it changes , the amount changed must be known.
The material should be relatively easy to measure.

21. Inject x gm of marker into compartment
DILUTION PRINCIPLE
Principle of mass conservation
Based on using a marker whose concentration can be measured.
Inject x gm of marker into compartment
measure concentration at equilibrium (y gm/L)
Since concentration = mass/ volume
Volume = mass / concentration = x/y L
C1V1=C2V2

22. Measuring Compartment Size Indirect METHOD – INDICATOR (DYE) DILUTION TECHNIQUE (Law of Mass Conservation)
Based on concentration in a well-mixed substance that distributes itself only in the compartment of interest.
Compartment
Amount of
Tracer Lost
From
Compartment
(E)
Volume (V)
Amount of
Tracer Added
(A)
Tracer Concentration (C)
Concentration = Amount Injected
Volume of Distribution
Amount of Tracer Remained in Compartment = A - E
Compartment Volume = (A – E)/C

23. Indicators used for measuring plasma volume, ECF volume and total body H2O
Compartment
Criterion
Indicators
Plasma
Substance should not cross capillaries
Evans blue dye;
radioiodinated fibrinogen;
radioiodinated albumin
ECF volume
Substance should cross capillaries but not cross cell membranes
Isotonic solutions of sucrose, inulin, mannitol, NaCl
Total body H2O (TBW)
Substance distributes evenly in ICF & ECF
Heavy H2O, tritiated H2O, aminopyrine, antipyrine

24. Total Body H2O (TBW) Deuterated H2O (D2O) Tritiated H2O (THO)
Antipyrine 44 44

25. Blood volume /Markers used
Obtained from plasma volume and hematocrit
Total blood volume = Plasma volume/1- Hematocrit
Example: If the plasma volume is 4 liters and the hematocrit is 0.45, total blood volume is ?
=PLASME VOL X
100 -HCT
1.T-1824 (Evans blue dye) attaches to plasma proteins and is removed by the liver. Measures plasma volume
2. Radioactive labeled 125 i albumin
3. Cr51 (radioactive chromium) is incubated with red blood cells then injected
Measures total blood volume

26. Take this problem:
100 mg of sucrose is injected into a 70 kg man. The plasma sucrose level after mixing is 0.01 mg/ml. If 5 mg has been metabolized during this period, then, what is the ECF volume? 9.5 L 14 L 17.5 L 10 L
If 1mL of solution (10mg/mL) of dye is dispersed in chamber B and final concentration is the chamber is 0.01mg/mL. What is the volume in chamber B?
1000ml or 1L

27. Compartments with no Compartment-Specific Substance
Determine by subtraction:
How would you measure ICF volume?
Cannot be measured; it is calculated (estimated)..
ICF volume = Total body H2O – ECF volume
Interstitial volume
Can not be measured directly
Interstitial Fluid Volume (ISFV). ISFV = ECFV - PV 47 47

28. Measurement of other spaces
Extracellular volume
Na24
Cl35
Inulin
Sucrose
Mannitol
Sulfate
I125 iothalamate
Disperse in plasma and interstitial fluid, but not permeable to cell membrane
min for dispersion to extracellular fluid

29. Determining body fat: Technique: bioelectric impedance technique
Principle:
Body fluids conduct electricity well;
But fat is anhydrous and therefore is a poor conductor of electricity;
The resistance to flow of a small current between points on the body is proportional to fat mass.

30. Lean body mass (LBM) Definition: LBM is fat free mass
Total body mass = fat mass + fat free mass
Note: fat is relatively anhydrous
Note: the H2O content of LBM is constant
H2O content of LBM is constant - 70 ml /100 g tissue

31. Take this problem:
In a healthy adult male weighing 70 kg, total body H2O (TBW) was measured to be 42 L. What is his lean body mass (LBM)? What is his fat mass?
Given TBW = 42 L
Assume all this H2O is in LBM & that fat is H2O free
We know that H2O content of LBM is 70 ml/100 g
Thus, if TBW is 42 L, LBM = 60 kg
Since he weights 70 kg, his fat mass is = 10 kg