Body Fluid
Latha Rajendra Kumar, MD
Learning Objectives
• To understand the various compartments that
the body fluid are distributed.
• To be able to calculate the body fluid
distributions when values are given
• To know the methods of measurements of
compartments
• To understand the what is edema
Body composition
In average young adult male:
of body %
weight
Body composition
Protein
substances
Fat
Mineral
Water
and
related
%18
%15
%7
%60
Water content in body is divided into 2 compartments:
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•
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1. Extracellular fluid (ECF): (internal environment or the
milieu intérieur)
fluid outside the cells.
 1/3 volume of fluids in body ( 33% of total body water).
- contains ions & nutrients needed for cellular life.
2. Intracellular fluid (ICF):
- fluid inside the cells.
 2/3 volume of fluids in body ( 67% of total body
water).
Fluid Compartments
 60% of body weight
Extracellular fluid
( 1/3)
Intracellular fluid
( 2/3)
 20% of body wt
 40% of body wt
 33% of TBW
Plasma
 25% of ECF
 5% of body wt
Interstitial fluid
75% of ECF
 15% of body wt
 67% of TBW
Transcellular fluid
CSF
Intraocular
Pleural
Peritoneal
Pericardial
Synovial
Digestive
secretions
• The percentage of total body water: 45-75%
• Intracellular compartment
– 2/3 of body water (40% body weight)
• Extracellular compartment
–
–
–
–
1/3 of body water (20% body weight)
the blood plasma (water=4.5% body weight)
interstitial fluid and lymph (water=15% body weight)
transcellular fluids: e.g. cerebrospinal fluid, aqueous
humor (1.5% BW)
• Distribution of substances within the body is NOT
HOMOGENEOUS.
So here is the summary of the 5
compartment model:
Here are the differences between ECF
and ICF:
ECF
Cations:
Na(+(142)mmol/L
K)4.2( +
Mg)0.8( +2
ICF
Anions:
Cations :
Cl)108( - Na)14( +
HCO3
K)140( +
Mg20( +2
Nutrients:
O ,2glucose, fatty acids & ,
amino acids.
Wastes:
CO ,2Urea, uric acid ,
excess water & ,ions.
Anions:
Cl)4( HCO)10( -3
Phosphate
ions
Nutrients:
High concentrations of proteins.
Body Water Distribution
• Individual variability (lean body mass)
– 55 - 60% of body weight in adult males
– 50 - 55% of body weight in adult female
– ~42 L For a 70 Kg man.
•
• Q. Calculate TBW for a 70 kg man.
•
• TBW = 60% of body weight
• TBW = 60% X 70 = 42 L of water
STEADY STATE OF WATER
Amount Ingested = Amount Eliminated
ELECTROLYTE LOSS:
• Occurs in the following conditions:
• Renal excretion
• Stool losses
• Sweating
• Abnormal routes: e.g.. vomit and diarrhea
FACTORS AFFECTING Total Body Water
• varies depending on body fat:
– infant: 73%
– male adult: 60%
– female adult: 40-50%
– effects of obesity
– Old age 45%
COMPOSITION OF BODY FLUIDS:
CATIONS
(mmol/l)
Na
K
Ca
Mg
ANIONS
(mmol/l)
Cl
HCO3
Protein
HPO4
Plasma
142
4.2
1.3
0.8
Ü
Interstitial Intracellul
ar
139
14
4.0
140
1.2
0
0.7
20
Ü
Ü
108
24.0
1.2
2.0
108
28.3
0.2
2.0
4.0
10
4.0
11
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METHODS OF MEASUREMENTS
Quantity = volume x concentration
Volume = quantity of dye
-----------------concentration of dye
Volume = quantity administered - quantity excreted
____________________________________
Concentration
INDIRECT METHOD – INDICATOR (DYE) DILUTION TECHNIQUE
PRINCIPLE
– YOU HAVE TO SELECT A SUITABLE DYE OR RADIO-ISOTOPE
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V= VOLUME OF FLUID
A= TOTAL AMOUNT OF DYE USED
E= AMOUNT OF DYE EXCRETED OR LOST .
C= CONCENTRATION
FORMULA : V=A-E/C
INTERSTITIAL FLUID= ECF – Plasma Volume
INTRACELLULAR FLUID = TBW – ECF
Dye Dilution Principle
• Different substances can be used to measure different fluid compartments
• total body water: tritiated water or deuterium, antipyrine, aminopyrine
• extracellular fluid: inulin , saccharides e.g. sucrose, inulin,
mannitol,diffusible inons e.g. sulphate, sodium, thiosulphate, bromide,
chloride. Those substances that disperse in the plasma and interstitial fluid
but do not permeate the cell membrane.These disperse well in 30 to 60
minutes.
• ICF= Total body water- ECF
• Intracellular fluid may then be estimated by subtracting extracellular fluid
from total body water.
• If total body water is 42 L and ICF = 28 L , calculate ECF?
• blood plasma: Evans blue , radioactive labeled 125 I albumin . Substance
shouldn’t penetrate capillary membrane but remains in the vascular
space.
• Interstitial fluid volume= ECF-PV
• If plasma volume is 3 liters, how much is interstitial fluid?
Substances used for measuring body
fluids:
Compartment
TBF
ECF
Plasma
Substances
Antipyrine
D2O
H3O
Innulin
Mannitol
Radio sulfate
Evans Blue
131 I- Albumin
51 Cr- Erythrocyte
• ICF = TBF - ECF
•
ISF = ECF – plasma
•
• TOTAL BLOOD VOLUME =
• PLASMA VOL X 100
•
----------------------•
1 -HCT
CRITERIA FOR A SUITABLE DYE
• Must mix evenly throughout the compartment
• Non toxic
• Must have nto effect of its own on the
distribution of water 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.
Dehydration
• Definition. Dehydration is an ambiguous term
that does not distinguish between simple
water loss and loss of Na+.
• Both water loss and Na+ loss are associated
with a decrease in the ECF volume, which is
determined by the amount of Na+ in the body
and not by the Na+ concentration in the
plasma.
Edema
• Edema is observable swelling from fluid
accumulation in body tissues. Mainly in
extracellular space and in interstitial space.
• Edema most commonly occurs in the feet and
legs, where it is referred to as peripheral
edema. The swelling is the result of the
accumulation of excess fluid under the skin in
the spaces within the tissues