1 ADVANCED PHYSIOLOGY FLUID & ELECTROLYTES Part 1 Instructor Terry Wiseth

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ADVANCED PHYSIOLOGYADVANCED PHYSIOLOGY

FLUID & FLUID & ELECTROLYTESELECTROLYTES

Part 1Part 1

Instructor Terry WisethInstructor Terry Wiseth

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FLUID ELECTROLYTE FLUID ELECTROLYTE HOMEOSTASISHOMEOSTASIS

In a healthy individual fluid volume and electrolyte concentrations are maintained within strict homeostatic limits through the interaction of several organ systems

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FLUID ELECTROLYTE FLUID ELECTROLYTE HOMEOSTASISHOMEOSTASIS

Total body water (TBW) can be divided by cell membranes into two main compartments:1) Extracellular fluid (ECF)1) Extracellular fluid (ECF)

fluid outside cells1/3 of total body water

2) Intracellular fluid (ICF)2) Intracellular fluid (ICF)fluid inside cells2/3 of total body water

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FLUID ELECTROLYTE FLUID ELECTROLYTE HOMEOSTASISHOMEOSTASISThe ECFECF is further divided into:

1) Blood plasma (80%)1) Blood plasma (80%)2) Interstitial fluid (20%)2) Interstitial fluid (20%)

These two ECF compartments are separated by a capillary membrane

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FLUID COMPARTMENTSFLUID COMPARTMENTS

Effectively there are three compartments1) Intracellular1) Intracellular2) Interstitial2) Interstitial3) Plasma3) Plasma

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FLUID COMPARTMENTSFLUID COMPARTMENTS

CYTOPLASMCYTOPLASM

INTERSTITIALINTERSTITIALFLUIDFLUID

PLASMAPLASMA(intracellular)(intracellular)

(extracellular)(extracellular)

capillarycapillary

cellcell

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ELECTROLYTESELECTROLYTESDissolved ions in the:

Cell, interstitial fluid, bloodPotassium (K)Sodium (Na)Calcium (Ca)Magnesium (Mg)Chlorine (Cl)Bicarbonate (H2CO3) Proteins (Pr)

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ELECTROLYTESELECTROLYTESThere are three key concepts in

consideration of fluid and electrolyte management:1) Cell Membrane Permeability1) Cell Membrane Permeability2) Osmolarity2) Osmolarity3) Electroneutrality3) Electroneutrality

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ELECTROLYTESELECTROLYTESCell Membrane PermeabilityCell Membrane Permeability

Refers to the ability of a cell membrane to allow certain substances to pass freely

Other substances like charged ions (NaNa++) cannot cross the membrane and are trapped on one side of itH2O

Na+

Na+

H2O

Na+

Na+

Na+

H2O

H2O

H2O

H2O

H2O

H2O

Na+

Na+

Na+

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ELECTROLYTESELECTROLYTESOsmolarityOsmolarity is a property of

particles in solutionIf a substance

can dissociate insolution, it willcontribute to theosmolarity of thesolution

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ELECTROLYTESELECTROLYTESThe principle of ElectroneutralityElectroneutrality

means that the overall number of positive and negative charges balances

For instance, in conditions like renal tubular acidosis where HCO3

- is lost, chloride is retained

Cl-

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ELECTROLYTESELECTROLYTESWhen the body is “In fluid

balance” it means that the various body compartments (cells, tissues, organs) contain the required amount of fluids to carry out normal bodily functions

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ELECTROLYTESELECTROLYTESFluid balance and electrolyte

balance are inseparableIn a healthy individual, the

volume of fluid in each compartment remains stable

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ELECTROLYTESELECTROLYTESLoss of electrolytes can have

serious consequences for the body

In severe dehydration, the loss of electrolytes can result in circulatory problems such as tachycardia (rapid heart beat) and problems with the nervous systemsuch as loss ofconsciousnessand shock

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ELECTROLYTESELECTROLYTESElectrolytes serve three

general functions:1) Maintain normal 1) Maintain normal

metabolismmetabolism2) Maintain proper fluid 2) Maintain proper fluid

movement between movement between compartmentscompartments

3) Maintain the acid-base 3) Maintain the acid-base balancebalance

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ELECTROLYTE COMPOSITION OF ELECTROLYTE COMPOSITION OF PLASMA AND INTERSTITIAL PLASMA AND INTERSTITIAL

FLUIDFLUID(meq/liter) PLASMA INTERSTITIAL

FLUIDNa+ 140.0 145.5K+ 4.5 4.8Ca++ 5.0 2.8Mg++ 1.5 1.0Cl - 104.0 116.6HCO3

- 24.0 27.4PROTEIN 14.0 8.0

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ELECTROLYTESELECTROLYTES

0 50 100 150 200

Na+

K+

Ca++

Mg++

Cl-

HCO3-

Protein

INTERSTITIALFLUID

PLASMA

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ELECTROLYTESELECTROLYTES

Na+

K+

Ca++

Mg++

Cl-

HCO3-

ProteinPLASMA INTERSTITIALFLUID

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IONS AND MOLECULESIONS AND MOLECULES

IonsIons are charged atoms

ex: Na+, Cl-, Mg++

MoleculesMolecules are formed when two or more atoms or ions are combined

ex: H2O, C6H12O6, NaCl

Na+ Cl-

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MOVEMENT OF BODY MOVEMENT OF BODY FLUIDSFLUIDSFluid moves between the

compartments of the body through various mechanisms

Substances leave and enter capillaries via three mechanisms:1) Vesicular transport1) Vesicular transport2) Diffusion2) Diffusion3) Bulk flow3) Bulk flow

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MOVEMENT OF BODY MOVEMENT OF BODY FLUIDSFLUIDSVesicular transport and diffusion

are associated with the movement of solutessolutes (electrolytes)(electrolytes)

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MOVEMENT OF BODY MOVEMENT OF BODY FLUIDSFLUIDSBulk flow is the most important

process for the maintenance of relative volumesvolumes (fluids) (fluids) of blood and interstitial fluidBulk flow involves the

movement of both solvent (fluids) and solute into the interstitial space

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MOVEMENT OF IONS AND MOVEMENT OF IONS AND MOLECULESMOLECULES

Ions and molecules pass through membranes by:Simple DiffusionPassage through channelsFacilitated DiffusionActive Transport (Na-K pum

p)

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CELL MEMBRANECELL MEMBRANE

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FLUID COMPARTMENTSFLUID COMPARTMENTSDescribes the distribution of water

in the bodyFluid compartments are separated

by semipermeable membranessemipermeable membranesCapillary wall separates the plasma and the interstitial fluid

Cell membrane separates the cytoplasm and interstitial fluid

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FLUID COMPARTMENTSFLUID COMPARTMENTS

CAPILLARY WALLCAPILLARY WALL

CELL MEMBRANECELL MEMBRANEINTERSTITIALINTERSTITIAL

FLUIDFLUID

PLASMAPLASMA

CYTOPLASMCYTOPLASM

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FLUID SHIFTSFLUID SHIFTS

Fluid shifts may occur as the result of disease or injury

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FLUID SHIFTSFLUID SHIFTS

Accumulations of fluids in a tissue or in a body cavity is called third space third space compartmentcompartmentEx: liver diseaseliver disease may lead to

significant accumulations of fluid in the peritoneal cavityRepresents a fluid loss as it is trapped

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FACTORS CONTROLLING FACTORS CONTROLLING EXCHANGES OF FLUIDSEXCHANGES OF FLUIDS

1) Diffusion1) Diffusion

2) Filtration2) Filtration

3) Hydrostatic Pressure 3) Hydrostatic Pressure

4) Osmotic (Oncotic) 4) Osmotic (Oncotic) PressurePressure

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DIFFUSIONDIFFUSIONWater, small molecules and

ionsMovement of molecules from

areas of higher concentration to areas of lower concentration

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FILTRATIONFILTRATIONNet flow of water is due to overall

effect of pressure on both sides of a membrane

Fluid is filtered out of capillaries in response to changes in:

1) Hydrostatic Pressures1) Hydrostatic Pressures2) Oncotic (Osmotic) Pressures2) Oncotic (Osmotic) Pressures

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HYDROSTATIC PRESSURE HYDROSTATIC PRESSURE (HP)(HP)

Fluid pressureEx: blood pressure in the capillariesEx: blood pressure in the capillaries

H2O H2O H2O H2OH2OH2OH2OH2O

H2O H2O

H2O H2O

8

4

6

6

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HYDROSTATIC PRESSURE HYDROSTATIC PRESSURE (HP)(HP)

Fluid pressureEx: blood pressure in the capillariesEx: pressure exerted by interstitial Ex: pressure exerted by interstitial

fluidfluid

H2OH2O

H2O

H2OH2O

H2O

H2OH2O

H2O H2O

H2O H2O

8

4

6

6

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HYDROSTATIC PRESSURE IN PLASMAHYDROSTATIC PRESSURE IN PLASMABlood Pressure at ArterialArterial end

of capillaries is 30 mm Hg30 mm HgBlood Pressure at VenousVenous end

of capillaries is 10 mm Hg10 mm HgDifference in pressure forces

fluid out of plasma to the interstitial fluid

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HYDROSTATIC PRESSURE IN INTERSTITIAL HYDROSTATIC PRESSURE IN INTERSTITIAL FLUIDFLUIDHydrostatic pressure in interstitial

space is -- 6 mm Hg 6 mm HgSupplies a pulling force (suction)

drawing fluid out of the capillaries

The lymphatic system drains interstitial fluid creating a negative interstitial pressure

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OSMOTIC (ONCOTIC) OSMOTIC (ONCOTIC) PRESSUREPRESSURE

Drawing force resulting from the pressure created by presence of protein dissolved in:CytoplasmPlasmaInterstitial fluid

Pressure which develops when there is net movement of water across a membrane (osmosis)(osmosis)

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OSMOTIC (ONCOTIC) OSMOTIC (ONCOTIC) PRESSUREPRESSURE

Pressure created is directly proportional to solute concentrationThus osmotic pressure is

dependent on the concentration of urea, glucose, amino acids, electrolytes and proteins

Oncotic pressureOncotic pressure definespressures which are the resultof protein concentration differences

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ONCOTIC PRESSURE IN ONCOTIC PRESSURE IN PLASMAPLASMA

Oncontic pressure at the arterial end of capillaries is 28 mm Hg28 mm Hg

Oncotic pressure of interstitial fluid is 5 mm Hg5 mm HgDue to a higher protein

concentration in plasma

Capillary

Pr- Pr-Pr- Pr- Pr-

Pr-Pr-

Pr-

Pr-

Pr-

Pr-

Pr-

Pr-

Pr-

Pr-Pr-

Pr- Pr-

Pr-Pr- Pr-

H2O H2O

H2O H2O

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ONCOTIC PRESSUREONCOTIC PRESSURE

Capillary

H2O H2O

PROTEIN (OP)

INTERSTITIAL FLUIDPROTEIN (OP)

Opposing oncotic pressure (OP) inside and Opposing oncotic pressure (OP) inside and outside of a capillary. A higher protein outside of a capillary. A higher protein concentration in plasma as compared to concentration in plasma as compared to interstitial fluid, thus it has a greater interstitial fluid, thus it has a greater oncotic pressureoncotic pressure

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CAPILLARY-INTERSTITIAL CAPILLARY-INTERSTITIAL FLUID EXCHANGESFLUID EXCHANGES

Hydrostatic and osmotic (oncotic) pressures create opposing inward and outward forces on the capillary

CapillaryHydrostatic Pressures

Osmotic Pressures

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OUTWARD FORCESOUTWARD FORCES

Arterial end of capillary exerts hydrostatic pressure (30 mm (30 mm Hg)Hg)

Capillary 30 Hydrostatic Pressures

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OUTWARD FORCESOUTWARD FORCESInterstitial fluid oncotic pressure

(5 mm Hg)(5 mm Hg)Negative interstitial fluid pressure

(-6 mm Hg)(-6 mm Hg)Total outward pressure 41 mm Hg41 mm Hg

Capillary30

Hydrostatic

Pressures

Osmotic Pressure

s

5

6 Interstitial Fluid (Pull)

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INWARD FORCESINWARD FORCESPlasma oncotic pressure (28 mm (28 mm

Hg)Hg)

Capillary

28Osmotic

Pressures

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INWARD FORCESINWARD FORCESNet outward filtration of 13 mm Hg13 mm Hg

results in plasma fluid loss41 mm Hg - 28 mm Hg = 13 mm 13 mm

HgHg

Capillary

28Osmotic Pressure

s

30Hydrostat

ic Pressures

Osmotic Pressure

s

5

6 Interstitial Fluid (Pull)

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Opposing forces that influence fluid shifts across the capillary wall. The net effect is outflow of fluid (41 - 28) with a net pressure of 13

Arterial endof capillary

30 mm Hg (HP) 28 mm Hg (OP)

Interstitial fluid

- 6 mm Hg(HP)

5 mm Hg(OP)

Total pressureTotal pressuredrawing fluid outdrawing fluid out

Inward Inward drawingdrawing

forceforce

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ABNORMAL CAPILLARY ABNORMAL CAPILLARY DYNAMICSDYNAMICS

Loss of protein and fluid from plasma to interstitial fluid is provided a return to the circulatory system by way of the lymphatic system

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ABNORMAL CAPILLARY ABNORMAL CAPILLARY DYNAMICSDYNAMICS

Increased capillary fluid loss occurs when there is:1) Increased Capillary 1) Increased Capillary

Hydrostatic PressureHydrostatic Pressure2) Increased Interstitial Fluid 2) Increased Interstitial Fluid

Oncotic PressureOncotic Pressure3) Decreased Plasma Oncotic 3) Decreased Plasma Oncotic

PressurePressureAccumulations of fluid in

interstitial spaces is called edemaedema

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CONDITIONS FOR EDEMACONDITIONS FOR EDEMA

CapillaryCapillaryIncreasedIncreasedHPHP

- HP OP

OPOP

Interstitial fluidInterstitial fluid

Increased capillary Hydrostatic Pressure

(HP)

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CONDITIONS FOR EDEMACONDITIONS FOR EDEMA

CapillaryCapillaryHPHP

- HP- HP OPOP

DecreasedDecreasedOPOP

Interstitial fluidInterstitial fluid

Decreased plasma OncoticDecreased plasma OncoticPressure (loss of protein)Pressure (loss of protein)

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CONDITIONS FOR EDEMACONDITIONS FOR EDEMA

CapillaryCapillaryHPHP

- HP- HP IncreasedIncreasedOPOP

OPOP

Interstitial fluidInterstitial fluid

Increased Oncotic PressureIncreased Oncotic Pressurein interstitial fluidin interstitial fluid

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EDEMAEDEMAVarious liver diseases that

result in decreased protein synthesis lead to edema

Noxious gases, inflammation (pneumonia), or respiratory burns may cause increased permeability of pulmonary capillaries with loss of proteins and fluid

Cause of pulmonary edema in these cases may be a combination of factors

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CAUSES FOR EDEMACAUSES FOR EDEMAI) MalnutritionII) Capillary wall damageIII) Obstructed lymph flowIV) Fluid accumulation in the lungsV) Left ventricle heart failureVI) Congestive heart failureVII) GlomerulonephritisVIII) Nephrotic syndromeIX) Large doses of blood or salt

sol.

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I) MALNUTRITIONI) MALNUTRITIONDecreased or cessation of food

intake leads to decreased synthesis of protein by the liver

Marked lowering of plasmaproteinDecreased oncotic

pressure causes a lowered tendency to draw waterinto the capillaries

Thus fluids accumulate outside the capillaries

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MALNUTRITIONMALNUTRITION

CapillaryCapillary

NormalNormal

ProteinProtein DecreasedDecreasedProteinProtein

MalnutritionMalnutrition

HH22OO HH22OODecreased ProteinDecreased Protein

In malnutrition, there is a decreased synthesis of protein by the liver, resulting in a lowered protein level in plasma. A decrease in oncotic pressure causes a diminished tendency to draw water into capillaries. The net result is edema

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KWASHIORKOR AND KWASHIORKOR AND MARASMUSMARASMUS

Reduced osmolarity from lack of protein in the diet results in a fluid shift, as more water moves out of the capillaries into the interstitial spaces like the peritoneal cavity

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II) CAPILLARY WALL II) CAPILLARY WALL DAMAGEDAMAGEDamage which increases capillary

permeability to proteinsEx: exposure to certain

chemicalsVenomsBacterial toxinsInflammatory response

Protein loss leads to decrease in capillary oncotic pressure

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Excess fluids and proteins in interstitial fluid are collected and returned to plasma by lymphatic vessels

Tumor or surgical removal of lymph nodes can obstruct flow which leads to edema

III) OBSTRUCTED LYMPH III) OBSTRUCTED LYMPH FLOWFLOW

mammogram

abdominal surgery

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IV) PULMONARY EDEMAIV) PULMONARY EDEMAFluid accumulates in alveoli of

the lungs

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IV) PULMONARY EDEMAIV) PULMONARY EDEMAPulmonary capillaries are more

permeable to proteins than capillaries in other parts of the bodyThus lungs are more

susceptible to edema

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Tendency toward increased oncotic pressure (water drawing force)

Interstitial fluid space is limited in lung tissue

Thus excessive fluid in the interstitial fluid space leaks readily into the alveoli interfering with gas exchange

PULMONARY EDEMAPULMONARY EDEMA

RBC

Alveoli

Interstitium

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ALVEOLAR EDEMAALVEOLAR EDEMA

In this section of lung the alveolar walls are congested (arrow A)(arrow A) and the alveolar spaces are filled with pink fluid (arrow B)(arrow B). A few alveolar macrophages (arrow C)(arrow C) are present but there is no significant inflammation

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PULMONARY EDEMAPULMONARY EDEMAFactors which protect the lungs

from fluid accumulations:1) A high rate of lymph flow 1) A high rate of lymph flow

away from the lungsaway from the lungs2) Pulmonary capillary 2) Pulmonary capillary

pressure that is lower than pressure that is lower than systemic capillary pressuresystemic capillary pressure

Great deal of congestion is present as well as fluid in the

alveoli

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PULMONARY EDEMAPULMONARY EDEMA

Principles of water balance in the lungs are the same as in peripheral tissues

Any condition that causes increased capillary hydrostatic pressure, decreased capillary oncotic pressure, or increased capillary permeability may lead to pulmonary edema

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V) LEFT VENTRICLE HEART V) LEFT VENTRICLE HEART FAILUREFAILURE

Pulmonary edema is characteristic of various forms of heart failure

If the left ventricle of the heart fails as a pump:Pulmonary circulation is slowed

and there is a buildup of blood in the pulmonary vessels

Blood pressure increases

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HYDROSTATIC EDEMAHYDROSTATIC EDEMA

This radiograph demonstrates pulmonary arteriesthat are much larger than their accompanying bronchi (A). In addition the bronchial walls are thickened. The patient was treated with diureticsand the subsequent scan (right) shows normal appearing bronchi (B) in which the bronchialwalls are thin and the pulmonary artery and bronchus are the same size

pulmonaryartery

pulmonaryartery

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VI) CONGESTIVE HEART VI) CONGESTIVE HEART FAILUREFAILURE

The heartfails as apump

Increased pulmonary venous and capillary pressure because of increased blood volume (increased hydrostatic pressure)

coronary bypass

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VII) VII) GLOMERULONEPHRITISGLOMERULONEPHRITIS

Inflammatory kidney diseaseEdema is caused by fluid

retentionThus there is increased

capillary hydrostatic pressure

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VIII) NEPHROTIC VIII) NEPHROTIC SYNDROMESYNDROMEUrinary protein loss and decreased

plasma proteinGeneralized edema as the result of

lowered plasma oncotic pressure

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Pulmonary edema is the result of increased blood volume

Thus increased hydrostatic pressure

Individuals with heart or kidney disease are especially susceptible

IX) ADMINISTRATION OF LARGE IX) ADMINISTRATION OF LARGE AMOUNTS OF BLOOD OR SALT AMOUNTS OF BLOOD OR SALT

SOLUTIONSSOLUTIONS

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INTERSTITIAL FLUID-INTERSTITIAL FLUID-CELLULAR DYNAMICSCELLULAR DYNAMICS

Water movement between cells and the interstitial fluids

Electrolyte composition is a major factor in this exchangeOsmotic pressure is the

drawing force

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ELECTROLYTE ELECTROLYTE CONCENTRATIONSCONCENTRATIONS

Meq/liter InterstitialFluid

MuscleCells

Na+ 145.5 12K+ 4.8 150Ca++ 2.8 0.0000001Mg++ 1.0 7Cl - 116.6 3HCO3

- 27.4 10PO4

- - - 2.3 116Protein - 8.0 40

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PRINCIPLE ELECTROLYTE PRINCIPLE ELECTROLYTE IN IN INTERSTITIAL FLUIDINTERSTITIAL FLUID

Meq/liter InterstitialFluid

MuscleCells

Na+ 145.5 12K+ 4.8 150Ca++ 2.8 0.0000001Mg++ 1.0 7Cl - 116.6 3HCO3

- 27.4 10PO4

- - - 2.3 116Protein - 8.0 40

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MAIN MAIN INTRACELLULARINTRACELLULAR IONSIONS

Meq/liter InterstitialFluid

MuscleCells

Na+ 145.5 12K+ 4.8 150Ca++ 2.8 0.0000001Mg++ 1.0 7Cl - 116.6 3HCO3

- 27.4 10PO4

- - - 2.3 116Protein - 8.0 40

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ELECTROLYTE ELECTROLYTE COMPARISONSCOMPARISONS

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FLUID IMBALANCEFLUID IMBALANCE

Fluid imbalance may occur and result in either: Cellular dehydrationCellular dehydration Cellular hydrationCellular hydration

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CELL DEHYDRATION IN CELL DEHYDRATION IN DIABETESDIABETES

H2OH2OH2OH2OH2OH2OH2OH2OH2O

glucose

Ex: diabetes Glucose concentrations increase

in extracellular fluidsIncreased conc. gradients outside

the cells draw water out of the cells by creating an osmotic pull

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CELL HYDRATIONCELL HYDRATIONNaNa++ ions predominate in

extracellular fluidThus NaNa++ plays a major role in

determining osmotic pressureLow NaNa++ in extracellular fluid

creates an intracellular osmotic pull on HH2200

decreased soluteconcentration

decreased osmoticpressure

hydration of cells

Na+ loss

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CELL HYDRATIONCELL HYDRATIONLow sodium levels can be

caused by diuretics, vomiting or low Na+ intake

If low sodium levels are combined with excess water intakeCell hydration is

exaggerated

Excess water intake

Low sodiumlevels

+ =Cell hydration

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EFFECTS OF IMBALANCE EFFECTS OF IMBALANCE ON COMPARTMENTSON COMPARTMENTS

Intravascular (plasma) compartment is the most likely to be affected by volume changes first

Interstitial and intracellular compartments are less likely to be affected and thus represent fluid reservoirsfluid reservoirs

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SUDDEN LOSS OR GAINS SUDDEN LOSS OR GAINS OF FLUIDSOF FLUIDS

Sudden loss or gain of fluids affect only intravascular compartmentsex: hemorrhage

Both compartments sharelosses or gains equally ifthey occur over a period of hours

Significant shifts of fluids between compartments require several hours

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LOSS OF HYPOTONIC LOSS OF HYPOTONIC FLUIDFLUIDLoss of hypotonic fluidhypotonic fluid (solute(solute

concentration less than that ofconcentration less than that of plasma)plasma) has a concentrating effect on extracellular fluidThis results in an increase of

osmotic pressureWater is drawn out of cells

in response to increasedextracellular osmoticpressure

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FLUID BALANCE FLUID BALANCE DISORDERSDISORDERS

Total volume of water in the body is 60% of body weightIntracellular fluidIntracellular fluid === 67% === 67%PlasmaPlasma =========== 8% =========== 8%Interstitial fluidInterstitial fluid ===== 25% ===== 25%

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REGULATION OF FLUID REGULATION OF FLUID INTAKEINTAKEThirst is a powerful

regulator of fluid consumption

Thirst center in the hypothalamushypothalamus is stimulated by: 1) 1) Cellular Cellular

dehydrationdehydrationInadequate intake of water

Increase in extracellular solute concentration

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THIRSTTHIRST2)2) Decreased salivary productionDecreased salivary production

Dry sensation of the mucosa of the mouth and pharynx

3)3) Increased blood osmotic Increased blood osmotic pressurepressureStimulates osmoreceptors in the hypothalamus which in turn stimulate the thirst centerof the hypothalamus

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THIRSTTHIRST4)4) Decreased blood volume Decreased blood volume

(decreased blood pressure)(decreased blood pressure)Stimulates the release of reninrenin by the kidney

Renin promotes synthesis of angiotensin IIangiotensin II whichaffects the thirstcenter of thehypothalamus

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STIMULATION OF THIRST BY DEHYDRATIONSTIMULATION OF THIRST BY DEHYDRATIONdehydration

decreased flowof saliva

increased bloodosmotic pressure

decreasedblood volume

dry mouthand pharynx

stimulates osmoreceptorsin hypothalamus

decreased blood pressure

increased renin releaseby juxta-glomerular

cells of kidney

increasedangiotensin II

production

stimulates thirst centerin hypothalamus

increases thirst

increases fluid intake

increases body water to normallevel and relieves dehydration

1

2

3

4

5

6

7

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REGULATION OF FLUID REGULATION OF FLUID LOSSLOSSFluid loss is adjusted by:

Antidiuretic hormone (ADH)Vasopressin

Atrial natriuretic peptide (ANP)Aldosterone

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REGULATION OF FLUID REGULATION OF FLUID OUTPUTOUTPUT

ADH and aldosterone slow fluid losses

ANP causes diuresis (increased urine production)

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DEHYDRATIONDEHYDRATION

If the body is dehydrated:Blood pressure fallsGlomerular filtration

decreasesWater is thus conserved

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EXCESSIVE FLUID IN EXCESSIVE FLUID IN BLOODBLOOD

Excessive fluid in the blood:Increased blood pressureIncreased glomerular filtrationIncreased fluid output

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EXTENSIVE SKINDESTRUCTION

OTHER FACTORS CAUSING EXCESSIVE OTHER FACTORS CAUSING EXCESSIVE FLUID RETENTIONFLUID RETENTION

HEAVY PERSPIRATION

HYPERTENSION

HYPERVENTILATION

VOMITING

DIARRHEA

EXCESSIVE FLUID

RETENTION

FEVER

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EFFECTS OF FLUID EFFECTS OF FLUID EXCESSEXCESSFluid excess initially affects the

extracellular compartmentsIncreased fluid volume can

result in cerebral, pulmonary or generalized edema

Usually the result of inadequateinadequate renal outputrenal output rather than fluid intake

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EFFECTS OF FLUID EFFECTS OF FLUID EXCESSEXCESSIf the retained water is hypotonichypotonic as

compared to plasma the effect is to dilute the extracellular fluidThis causes a decrease in

osmolalityosmolalityWhen interstitial fluid is dilute as

compared to intracellular fluid, water is drawn into the cells by osmotic pull

Results in increased cellularvolume and changes in cellfunction occurMost apparent in CNS tissue

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INTRAVENOUS INFUSIONINTRAVENOUS INFUSIONIf the total body water is increased

by IV infusion of an isotonic isotonic solutionsolution the result will be:Increased extracellular volume With little or no effect on cellular

volumeNet result is no change in solute

concentrations in plasma, interstitial fluids and intracellular fluid and no effect on cells

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INTRAVENOUS INFUSIONINTRAVENOUS INFUSIONInfusion of a hypertonic hypertonic

solutionsolution results in:Diffusion of both solute and

water into the interstitial fluid occurs

This concentration of solutes in interstitial fluid is higher than normalCreates an osmotic drawing force

Pulls water out of the cell

96

SUMMARY OF SUMMARY OF OVERHYDRATION OR WATER OVERHYDRATION OR WATER

INTOXICATIONINTOXICATION1) If the fluid is hypotonichypotonic2) If the fluid retained is isotonic isotonic

to plasma3) If the excess fluid is hypertonichypertonic

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HYPOTONICHYPOTONIC1) If the fluid is hypotonichypotonic

Increase in extracellular volumeA dilutional effectSubsequent cellular dehydration

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ISOTONICISOTONIC

2) If the fluid retained is isotonic isotonic to plasmaExpansion of the

extracellular compartmentNo effect on cells

99

HYPERTONICHYPERTONIC

3) If the excess fluid is hypertonichypertonicIncreased extracellular volumeCellular dehydration

100

CAUSES FOR CAUSES FOR OVERHYDRATIONOVERHYDRATION

1) Psychiatric disorder of compulsive water drinking (psychogenic psychogenic polydipsiapolydipsia) 10 -15 liters/day

2) Forced water ingestion as a form of punishment (child abusechild abuse)

101

CAUSES FOR CAUSES FOR OVERHYDRATIONOVERHYDRATION

3) Inappropriate ADH secretionADH also called VasopressinVasopressinPromotes water retention

(reabsorption) by increasing permeability of the collecting ducts in the kidney

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CAUSES FOR CAUSES FOR OVERHYDRATIONOVERHYDRATION

ADH is also a powerful vasoconstrictor of arteriolesHead trauma, lung cancers, pneumonia, CNS diseases, encephalitis

Some types of tumors secrete substances with ADH-like activity

103

DEHYDRATIONDEHYDRATIONEffects of a fluid deficit depend

on:VolumeRate of lossAmount of electrolytes lost

with water

104

HYPOTONIC LOSSHYPOTONIC LOSSSimple dehydration is sometimes

called hypotonic losshypotonic lossEffects of hypotonic fluid loss

(water loss exceeds solute loss) has a concentrating effectResults in increased

osmolality andhypernatremia(increased NaNa++

concentration)

105

HYPOTONIC LOSSHYPOTONIC LOSSWater is drawn out of cells into

the extracellular compartmentCell volume depletion

stimulates the release of ADHADH (antidiuretic hormone) and aldosteronealdosteroneADH mediates renal water

retentionAldosterone favors

NaNa++ and water retention

106

SUMMARY OF HYPOTONIC SUMMARY OF HYPOTONIC DEHYDRATIONDEHYDRATION

Immediate effect of water loss is hypernatremiahypernatremia

Physiological responses to correct the imbalance:Movement of cellular water to

extracellular compartmentsHormonal responses that

increase extracellular volume

H2

OH2

OH2

OH2

OH2

OH2

OH2

OH2

OH2

OH2

OH2

OH2

OH2

OH2

O

107

CAUSES FOR CAUSES FOR DEHYDRATIONDEHYDRATION

1) 1) Excessive sweatingExcessive sweating

2) 2) Insensible fluid lossInsensible fluid loss

3) 3) DiuresisDiuresis

4) 4) Diabetes insipidusDiabetes insipidus

108

CAUSES FOR CAUSES FOR DEHYDRATIONDEHYDRATION1) 1) Excessive sweatingExcessive sweating

Sweat is hypotonicMay result in hypernatremia

109

CAUSES FOR CAUSES FOR DEHYDRATIONDEHYDRATION

2) 2) Insensible fluid lossInsensible fluid lossFrom the skin or lungs

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CAUSES FOR DEHYDRATIONCAUSES FOR DEHYDRATION3) DiuresisDiuresis

Solute cleared from the blood by the kidney and not reabsorbed remains in the glomerular filtrate

This high solute concentration creates an osmotic pull that draws water in that directionResults in increasedurine output andwater loss

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DIURESISDIURESISMannitolMannitol (polysaccharide) is

sometimes used in cerebral edemaNon-reabsorbable solute and creates an osmoticpull on waterpromoting water loss

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CAUSES FOR CAUSES FOR DEHYDRATIONDEHYDRATION4) Diabetes insipidusDiabetes insipidus

Deficiency of ADHExcessive urination and thirst

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ELDERLYELDERLY

Older individuals havea decreased renalcapacity to save water

Significant if: Fluid intake is limited

(decreased diet) Insensible fluid loss is

increased (fever)

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ELDERLYELDERLYElderly are also susceptible to

water intoxicationIncreased ADH secretion

(stress of surgery, pneumonia, meningitis)

Reduction in renal blood flowDecreased urine volume and water retention

Heart failure, liverdisease, drug induced hypotension

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INFANTSINFANTSInfants have a greater

surface area compared to weightIncreased insensible fluid loss

Infants have less renal concentrating ability than an adult

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ENDENDFLUID AND FLUID AND

ELECTROLYTES ELECTROLYTES PART 1PART 1