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8/3/2019 Fluids Acid Base
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General Principles ofPathophysiology
The Cellular Environment
Fluids & ElectrolytesAcid-base Balance & Maintenance
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Topics
Describe the distribution of water in thebody
Discuss common physiologic electrolytes Review mechanisms of transport
osmosis, diffusion, etc
Discuss hemostasis & blood types
Discuss concepts of acid-base maintenance
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Distribution of Water
Total Body Weight/ Total Body Water
Intracellular - ICF (45%/75%)
Extracellular - ECF (15%/25%)
Intravascular (4.5%/7.5%)
Interstitial (10.5%/17.5%)
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Intra-
cellular
45%
31.5 kg
Interstitial
10.5 %
7.35 kg
Intra-
vascular
4.5%
3.15 kg
Total Body Weight
Fluid Distribution
Extracellular
CellMembrane
Ca
pillaryMembrane
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Fluid Distribution
Intra-
cellular
75%
31.5 L
Interstitial
17.5 %
7.35 L
Intra-
vascular
7.5%
3.15 L
Total Body Water
Extracellular
C
ellMembrane
Cap
illaryMembrane
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Total Body Weight
45.0%
4.5%
10.5%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
Intracellular Intravascular Interstitial
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Total Body Water
75.0%
7.5%
17.5%
0%
10%
20%
30%
40%
50%
60%
70%
80%
Intracellular Intravascular Interstitial
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Edema
Fluid accumulation in the interstitialcompartment
Causes:
Lymphatic leakage
Excessive hydrostatic pressure
Inadequate osmotic pressure
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Fluid Intake
Water from
beverages:
1600 ml (64%)
Water from
food:
700 ml
(28%)
Water from
metabolism:
200 ml (8%)
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Fluid Output
Water from
skin:
550 ml
(25%)
Water from
feces:
150 ml (5%)
Water from
lungs:
300 ml (11%)
Water from
urine:
1500 ml
(59%)
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Osmosis versus Diffusion
Osmosis is the netmovement of water
from an area of LOWsolute concentration toan area of HIGHERsolute concentration
across a semi-permeable membrane.
diffusion of water
in terms of [water]
Diffusion is the netmovement of solutes
from an area of HIGHsolute concentration toan area of LOWERsolute concentration.
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Silly definition stuff
Osmolarity =osmoles/L of solution
Osmolality =osmoles/kg of solution
Where an osmole is 1 mole (6.02 x 1023 particles)
The bottom line?
Use them synonymously!
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Tonicity
Isotonic
Hypertonic
Hypotonic
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Isotonic Solutions
Same solute concentration as RBC
If injected into vein: no net movement of
fluid
Example: 0.9% sodium chloride solution
aka Normal Saline
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Hypertonic Solutions
Higher solute concentration than RBC
If injected into vein:
Fluid moves INTO veins
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Hypotonic Solutions
Lower solute concentration than RBC
If injected into vein:
Fluid moves OUT of veins
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Affects of Hypotonic Solution on
Cell
CellSwellingCell
Swollen
CellRuptured
Cell
The [solute] outsidethe cell is lower than
inside. Water moves from low
[solute] to high[solute].
The cell swells andeventually bursts!
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Affects of Hypertonic Solution on
Cell
Cell
The [solute] outsidethe cell is higher than
inside. Water moves from low
[solute] to high[solute].
The cell shrinks!
Shrinking
Cell
Shrunken
Cell
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Infusion ofhypertonicsolution into veins
No fluidmovement
Fluidmovementinto veins
Fluidmovementout of veins
Infusion ofisotonic solution
into veins
Infusion ofhypotonic solutioninto veins
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Ion Distribution
0
50
100
150
50
100
150
mEq/L
Na+
K+
Cl-
PO4-
Protein-
Cations Anions
Extracellular
Intracellular
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Example of Role of Electrolytes
Nervous System
Propagation of Action Potential
Cardiovascular System
Cardiac conduction & contraction
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Cardiac Conduction / Contraction
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Composition of Blood
8% of total body weight
Plasma: 55%
Water: 90%
Solutes: 10%
Formed elements: 45%
Platelets
Erythrocytes
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Hematrocrit
% of RBC in blood
Normal:
37% - 47% (Female)
40% - 54% (Male)
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Blood Components
Plasma: liquid portion of blood
Contains Proteins
Albumin (60%) contribute to osmotic pressure
Globulin (36%): lipid transport and antibodies
Fibrinogen (4%): blood clotting
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Blood Components
Formed Elements
Erythrocytes
Leukocytes
Thrombocytes
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Erythrocytes
biconcave disc
7-8 mcm diameter
Packed with hemoglobin
4.5 - 6 million RBC/mm3 (males)
Anucleate
120 day life span
2 million replaced per second!
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Leukocytes
Most work done in tissues
5,000 - 6,000/mm3
Neutrophils (60-70%)
Basophils (Mast Cells) (
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Thrombocytes
Platelets
Cell fragments
250,000 - 500,000/mm3
Form platelet plugs
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Hemostasis
The stoppage of bleeding.
Three methods
Vascular constriction
Platelet plug formation
Coagulation
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Coagulation
Formation of blood clots
Prothrombin activator
Prothrombin Thrombin
Fibrinogen Fibrin
Clot retraction
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Coagulation
Prothrombin
Activator
ProthrombinThrombin
Fibrinogen Fibrin
Clot
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Fibrinolysis
Plasminogen
tissue plasminogen activator (tPA)
Plasmin
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Blood Types
Agglutinogens (Blood Antigens)
Agglutinins (Blood Antibodies)
Agglutination (RBC clumping)
ABO
Rh Antigens
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Type A Blood
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Type B Blood
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Type AB Blood
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Type O Blood
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Rh Antigens
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Bottom line of Acid-Base
Regulation of [H+]
normally about 1/3.5 million that of [Na+]
0.00004 mEq/L (4 x 10-8 Eq/L)
Dependent upon
Kidneys
Chemical Buffers
Precise regulation necessary for peakenzyme activity
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pH Effects on Enzyme Activity
pH
EnzymeActivity
activity
Peak Activity
activity
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Acid Base
Acids release H+
example: HCl -> H+ + Cl-
Bases absorb H+
example: HCO3- + H+ -> H2CO3
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pH is logarithmic
pH = log 1/[H+]
= - log [H+]
= - log 0.00000004 Eq/L
pH = 7.4
Think of pH as power of [H+]
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pH is Logarithmic
pH is inversely
related to [H+]
Small pH meanlarge [H+]
as
[H+]
pH
as
[H+]
pH
&
pH 7.4 = 0.00000004
pH 7.1 = 0.00000008
(it doubled!)
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Buffers Resist pH Changes
Weak acid & conjugate base pair
H2CO3 HCO3- + H+
Conjugate Acid conjugate base + acid
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Henderson-Hasselbalch Equation
pH = pKa + log [base]/[acid]
Ex:
= 6.1 + log 20/1 = 6.1 + 1.3
= 7.4
Key ratio is base: acid HCO3- : CO2 (standing in for H2CO3)
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pH Scale
0 : Hydrochloric Acid
1: Gastric Acid
2: Lemon Juice 3: Vinegar, Beer
4: Tomatoes
5: Black Coffee 6: Urine
6.5: Saliva
7: Blood
8: Sea Water
9: Baking Soda 10: Great Salt Lake
11: Ammonia
12: Bicarbonate 13: Oven Cleaner
14: NaOH
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Acid Base Compensation
Buffer System
Respiratory System
Renal System
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Buffer System
Immediate
CO2 + H20 H2CO3 H+ + HCO3
-
Equilibrium: 20 HCO3- to 1 CO2 (H2CO3)
Excessive CO2 acidosis
Excessive HCO3
- alkalosis
Simplified:
CO2 H+
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Question...
Is the average pH of the blood lower in:
a) arteries
b) veinsVeins!
Why?
Because veins pick up thebyproducts of cellular metabolism,
including
CO2!
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Respiratory System
Minutes
CO2 H+
Respiration : CO2: H+
Respiration : CO2: H+
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Renal System
Hours to days
Recovery of Bicarbonate
Excretion of H+
Excretion of ammonium
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Disorders
Respiratory Acidosis
Respiratory Alkalosis
Metabolic Acidosis
Metabolic Alkalosis
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Respiratory Acidosis
CO2 + H20 H2CO3 H+ + HCO3
Simplified:
CO2 H+
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Respiratory Alkalosis
CO2 + H20 H2CO3 H+ + HCO3
Simplified:
CO2 H+
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Metabolic Acidosis
H+ + HCO3 H2CO3 H20 + CO2
Simplified:
Producing too much H+
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Metabolic Alkalosis
H+ + HCO3 H2CO3 H20 + CO2
Simplified:
Too much HCO3
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Normal Values
pH: 7.35 - 7.45
PCO2: 35 - 45
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Abnormal Values
pH PCO2
Respiratory Acidosis
Respiratory Alkalosis
Metabolic Acidosis Normal
if compensatingMetabolic Alkalosis Normal
if compensating
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All Roads Lead to Rome!
Respiratory Opposes
Metabolic Equals(or doesnt oppose)
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Example:
pH = 7.25
PCO2 = 60
RespiratoryAcidosis!
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Example:
pH = 7.50
PCO2 = 35
MetabolicAlkalosis!
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Example:
pH = 7.60
PCO2 = 20
RespiratoryAlkalosis!
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Example:
pH = 7.28
PCO2 = 38
MetabolicAcidosis!
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Resources
A Continuing Education article on Acid-Base disturbances is available on our web
site at: http://www.templejc.edu/ems/resource.htm
A great online tutorial at:
http://www.tmc.tulane.edu/departments/anesthesiology/acid/acid.html
http://www.templejc.edu/ems/resource.htmhttp://www.templejc.edu/ems/resource.htm