Transcript Body fluids compositions, and their measurements

Body fluids compositions,
and their measurements
By: DR QAZI IMTIAZ RASOOL
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
Body as an open sytem
Body exchanges materials and energy
with its surroundings
Route
Range
(l/day)
Regulatory
influences
Insensible lungs
0.3-0.4
Atmospheric
vapor
pressure
(temperature)
Insensible skin
0.35-0.4
10x increase
in burn
victims
Sweat
0.1-2 (per
hour)
Temperature,
exercise
Feces
0.1-0.2
Diarrheal
disease
Urine
0.5-1.4-20
Body fluid
composition
FACTORS AFFECTING
Total Body H2O
varies depending on body fat:
1.
Infant: 73-80%
2. Male adult: 60%
3. Female adult: 40-50%
4. Effects of obesity
5. Old age 45%
6. Climate Level of physical activity
PERCENTAGE OF H2O IN TISSUES
FLUID COMPARTMENTS
EXTRA CELLUAR
FLUID
PLASMA
1.
2.
3.
4.
5.
6.
INTRA CELLULAR
(cytosol)FLUID
INTERSTITIAL
FLUID
CSF
Intra ocular
Pleural
Peritoneal
Synovial
Digestive Secretions
TRANSCELLULAR
FLUID
PERCENTAGE OF WATER IN TISSUES
Average 70 kg person
total body weight
42 litres total H2O
60%
28 l. Intracellular fluid (ICF)
40%
14 l. Extracellular fluid (ECF)
20%
% is important in fluid therapy
divided into ¾ ISF and ¼ plasma water
10.5 l. Interstitial fluid (ISF)
3.5 l. Plasma water
TISSUE
Skin
Muscle
Skeleton
Brain
Liver
Blood
Intestine
Adipose Tissue
% WATER
72
76
22
74.8
68.3
83.0
74.5
10.0
% BODY Wt.
18
41.7
16
2.0
2.3
8.0
1.8
10+
L of H2O
9.1
22.1
2.5
1.0
1.0
4.65
1.0
0.7
15%
5%
Regulation of H2O Intake
The hypothalamic thirst center is stimulated:
1. By a decline in plasma volume of 10%–15%
2. By increases in plasma osmolality of 1–2%
3. Via baroreceptor input, angiotensin II, and other
stimuli
1. Semipermeable membrane
2. Movement some solute obstructed
3. H2O (solvent) crosses freely
4. End point:
1. H2O moves until solute concentration on
both sides of the membrane is equal
2. OR, an opposing force prevents further
movement
Solutes – dissolved particles
1. Electrolytes – charged particles
1. Cations – positively charged ions
Na+, K+ , Ca++, H+
2. Anions – negatively charged ions
Cl-, HCO3- , PO43-
2. Non-electrolytes - Uncharged
1. Proteins, urea, glucose, O2, CO2
12
APPROXIMATE IONIC COMPOSITION OF THE
BODY H2O COMPARTMENTS
Ion
Cations
Na+
K+
Ca2+(ionized)
Mg2+(ionized)
Others
Total
Anions
ClHCO3HPO42-, H2PO4Proteins
Other
Total
Interstitial
fluid,
mmoles/L
Skeletal
muscle cell,
mmoles/L
142.0
4.3
2.5
1.1
4.0
154
145.1
4.4
2.4
1.1
10.0
140.0
1.0
17
153
168
114.0
24.0
1.0
1.5
10.0
154
117.4
27.1
1.2
0.1
6.2
153
4.0
7.0
40.0
3.0
84.0
138
Plasma,
mmoles/L
Plasma Interstitial Cell
H2O
H2 O
H2O
Balance of Starling Forces acting across the capillary
membrane
1. osmotic forces
2. hydrostatic forces
Plasma vs Interstitial Space
-Balance between Hydrostatic and Colloid Osmotic
forces across the capillary membranes
Intracellular vs Extracellular
1. Osmotic effect (e.g. electrolytes)
2. ICFV is NOT altered by: iso-osmotic changes in
extracellular fluid volume.
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 270-290 mOSM
Net Osmotic Force Development
Ionic composition very different
-Total ionic concentration very similar
-Total osmotic concentrations virtually identical
1.
2.
3.
4.
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.
Disorders of H2O Balance: Dehydration
1 Excessive loss of H2O from
ECF
(a) Mechanism of dehydration
2
ECF osmotic
pressure rises
Cells lose H2O
3 to ECF by
osmosis; cells
shrink
?
1. H2O moves out of
cells
ECF Osmolarity
ECF Osmolarity ?
1. H2O moves into the
cells
2. ICF Volume decreases
2. ICF Volume increases
(Cells shrink)
3. ICF Osmolarity
increases
(Cells swell)
3. ICF Osmolarity
decreases
4. Total body
4. Total body osmolari
osmolarity remains
higher than normal
remains lower than
normal
CRITERIA FOR A SUITABEL DYE.
BODY FLUID MARKER
1. Must mix evenly throughout the compartment
2. Non toxic, no physiological activity
3. Even mixing
4. Must have no effect of its own on the distribution of H2O
or other substances in the body
5. Either it must be unchanged during the experiment or if
it changes , the amount changed must be known.
6. The material should be relatively easy to measure.
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
Measuring Compartment
Size
Indirect METHOD – INDICATOR (DYE) DILUTION TECHNIQU
(Law of Mass Conservation)
Based on concentration in a well-mixed substance that distributes
itself only in the compartment of interest.
Compartment
Volume (V)
Amount of
Tracer Added
(A)
Tracer Concentration (C)
Concentration =
Amount of
Tracer Lost
From
Compartment
(E)
Amount Injected
Volume of Distribution
Amount of Tracer Remained in Compartment = A - E
Compartment Volume = (A – E)/C
Indicators used for measuring plasma volume, ECF
volume and total body H2O
Compartment Criterion
1.
Plasma
1.
ECF
volume
1.
Substance
should not cross
capillaries
Substance
should cross
capillaries but
not cross cell
membranes
Total
Substance
body H2O distributes
(TBW)
evenly in ICF &
ECF
Indicators
Evans blue dye;
2. radioiodinated fibrinogen;
3. radioiodinated albumin
Isotonic solutions of sucrose,
inulin, mannitol, NaCl
1.
Heavy H2O, tritiated H2O,
aminopyrine, antipyrine
Total Body H2O (TBW)
1.
Deuterated H2O (D2O)
2.
Tritiated H2O (THO)
3.
Antipyrine
Blood volume /Markers used
1. Obtained from plasma volume and hematocrit
2. Total blood volume = Plasma volume/1Hematocrit
3. Example: If the plasma volume is 4 liters and the
hematocrit is 0.45, total blood volume is ?
4. =PLASME VOL X 100
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
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
If 1mL of solution (10mg/mL) of
17.5 L
dye is dispersed in chamber B
10 L
and final concentration is the
chamber is 0.01mg/mL. What is
the volume in chamber B?
1000ml or 1L
Compartments with
no Compartment-Specific Substance
4.
Determine by subtraction:
How would you measure ICF volume?
Cannot be measured; it is calculated
(estimated)..
ICF volume = Total body H2O – ECF volume
5.
Interstitial volume
1.
2.
3.
1.
6.
Can not be measured directly
Interstitial Fluid Volume (ISFV).
ISFV = ECFV - PV
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
30-60 min for dispersion to extracellular fluid
Determining body fat:
Technique: bioelectric impedance technique
Principle:
1. Body fluids conduct electricity well;
2. But fat is anhydrous and therefore is a poor
conductor of electricity;
3. The resistance to flow of a small current
between points on the body is proportional
to fat mass.
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
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?
1. Given TBW = 42 L
2. Assume all this H2O is in LBM & that fat is H2O
free
3. We know that H2O content of LBM is 70 ml/100 g
4. Thus, if TBW is 42 L, LBM = 60 kg
5. Since he weights 70 kg, his fat mass is 70-60 =
10 kg