9315628 fluids and electrolytes
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Review: Plasma MembraneReview: Plasma Membrane
Phospholipid bilayerPhospholipid bilayer
Freely permeable toFreely permeable to non-polarnon-
polarmolecules (COmolecules (CO22, O, O22, steroids), steroids)
Impermeable to largeImpermeable to largepolar and
polar andchargedchar
ged molecules (ions,molecules (ions,proteins, glucose)proteins, glucose)
Generally permeable to water (though someGenerally permeable to water (though somecells require aquaporins)cells require aquaporins)
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60%Adult
64%12-24 months
70-80%Newborn infant
90%Premature infant
Approx water
content in body
Age group
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60%fluids
55%fluids
Total Body MassTotal Body Mass
female male
45%solids
40%solids
2/3Intra-
cellularfluid(ICF)
1/3(ECF)
80%
20%
Interstitialfluid
Plasma
Some fluid is lost from blood in theSome fluid is lost from blood in theinterstitial tissues, and returned by theinterstitial tissues, and returned by the
lymphatic system
lymphatic system
(also lymph and othermiscellaneous fluids)
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5
2/3 (65%) of TBW is intracellular (ICF)
1/3 extracellular water
25 % interstitial fluid (ISF)
5- 8 % in plasma (IVF intravascular fluid)
1- 2 % in transcellular fluids CSF, intraocular
fluids, serous membranes, and in GI, respiratory and
urinary tracts (third space)
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Function of ICF & ECF: ICF: is vital to normal cell function, its contain
solutes such as oxygen, electrolytes and glucose.
It provides a medium to metabolic process.
ECF: it is the transport system that carries
nutrients and waste product from the cell.
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The proportion of water decreases with aging because fat, age
and sex effect of total body water.
Infants have a greater proportion of extracellular fluid
than older children and adults.
Because extracellular fluid is more easily lost from
the body than intracellular fluid, infants are more at
risk of developing dehydration than older children and
adults (infants also have a larger surface area to body
mass ratio).
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NaNa++
ClCl--
HCOHCO33--
KK++
MgMg2+2+
POPO443-3-
++ ++ ++ ++-- -- -- --
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Electrolytes charged particles
Cations positively charged ions
Na+, K+ , Ca++, H+
Anions negatively charged ions
Cl-, HCO3- , PO4
3-
Non-electrolytes - Uncharged
Proteins, urea, glucose, O2, CO2
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ICF (mEq/L) ECF (mEq/L)
Sodium 20 135-145
Potassium 150 3-5
Chloride --- 98-110Bicarbonate 10 20-25
Phosphate 110-115 5
Protein 75 10
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oOsmolarity = solute/(solute+solvent)Osmolarity = solute/(solute+solvent)
o Osmolality = solute/solvent (Osmolality = solute/solvent (275-295 mOsm/L))
o Tonicity = effective osmolalityTonicity = effective osmolality
o Plasma osmolility = 2 x (Na) + (Glucose/18) +Plasma osmolility = 2 x (Na) + (Glucose/18) +
(Urea/2.8)(Urea/2.8)
o Plasma tonicity = 2 x (Na) + (Glucose/18)Plasma tonicity = 2 x (Na) + (Glucose/18)
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MW (Molecular Weight) = sum of the weights of
atoms in a molecule
mEq (milliequivalents) = MW (in mg)/ valence
mOsm (milliosmoles) = number of particles in a
solution
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Tonicity
Isotonic
Hypertonic
Hypotonic
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Cell in a
hypotonic
solution
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Cell in a
hypertonicsolution
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MOVEMENT OF BODY FLUIDSMOVEMENT OF BODY FLUIDS
Diffusion
Osmosis
FiltrationActive transport
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1. Osmosis:
Is the movement of water across cell
membranes, from the less concentrated solution
to more concentrated solution. In other word
water move toward higher concentration.
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Solutes are substance dissolved in liquid.
Crystalloid: salts that dissolved readily in to true solution.
Colloids: substance such as large protein molecules thatdo not dissolved in true solution.
Sodium is the major determinant of serum
osmolality.
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2. Diffusion:
Is the continual intermingling of molecules in liquid,
gases by random movement of the molecules.3. Filtration:
Is the process where by fluid and solutes moved
together across a membrane from one compartment to
another.
4. Active transport:
substance can move across cell membranes
from a less concentrated solution to amoreconcentrated one by active transport.
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Sodium and potassium concentrations in extra- and
intracellular fluids are nearly opposite
This reflects the activity of ATP-dependent sodium-potassium pumps (Na+-K+ ATPase)
Fl id M t AFl id M t A
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Fluid Movement AmongFluid Movement Among
CompartmentsCompartments
Continuous exchange and mixing of fluid amongcompartments - regulated by osmotic and hydrostatic
pressures
Net leakage of fluid from the blood is picked up by lymphatic
vessels and returned to the bloodstream
Exchanges between interstitial and intracellular fluids are
more complex due to the selective permeability of the cell
membranes
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An increase in ECF solute concentration [NaCl] would cause osmotic anvolume changes in the ICF.
Which way would water move, into or out of cells?
ICF is determined by the ECF solute concentration
solutesolute
solute
solute
solutesolute
solute
solute
solutesolute
More Solute = Less WaterLess Solute = More Water
Hypertonic Solution or
Hypotonic Solution?
solute
solute
solute
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O
H2O H2O
H2O
H2O
H2O
H2O
H2O
Which way will Water move?
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solutesolute
solute
solute
solutesolute
solute
solute
solutesolute
H2O
H2O
H2O
H2O
H2O
If the oncotic pressure in the interstitium increased, would this promotinhibit the re-entry of fluid in a capillary b
H2O
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Daily water intake must equal water outputDaily water intake must equal water output
Water IntakeWater Intake Water OutputWater Output
Stimulated byStimulated by thirstthirstcenter ofcenter ofhypothalamushypothalamus
OsmoreceptorsOsmoreceptorsdetect an increasedetect an increasein fluid osmolarityin fluid osmolarity
Thirst center inhibited byThirst center inhibited bydistension of stomach walldistension of stomach wall
SensibleSensible loss: urine,loss: urine,feces, noticible sweatfeces, noticible sweat
InsensibleInsensible loss:loss:respiration and non-respiration and non-noticible sweatnoticible sweat
Urine output is the primary regulator oUrine output is the primary regulator owater out (ADH from posterior pituitarywater out (ADH from posterior pituitarygland)gland)
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Water intake:
Ingested fluid (60%) and solid food (30%)
Metabolic water or water of oxidation (10%)
Water output:
Urine (60%) and feces (4%)
Lost via lungs and skin (28%), sweat (8%)
To remain properly hydrated, water intake must equal water output
Fluid Gain and Loss
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Why are you told to drink plenty of fluids when you have a fever?A fever increases water loss (maybe both insensible and sensible)
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The hypothalamic thirst center is stimulated by:A decline in plasma volume of 10%15%
Increases in plasma osmolality of 12%
Baroreceptor input, angiotensin II, etc.
Feedback signals that inhibit the thirst centers include:
Moistening of the mucosa of the mouth and throat
Activation of stomach and intestinal stretch receptors
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Hormonal regulationHormonal regulation
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Hormonal regulationHormonal regulation
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Regulation of ECFRegulation of ECF
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Body fluids are:
Electrically neutral
Osmotically maintained
Specific number of particles per
volume of fluid
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Ion transport
Water movement
Kidney function
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Water loss (output) exceeds water intake and the body isin negative fluid balance
A common sequala to hemorrhage, severe burns,prolonged vomiting or diarrhea, profuse sweating, water
deprivation, and diuretic abuseSigns and symptoms: dry mouth, thirst, dry flushed skin,
and oliguria
Prolonged dehydration may lead to weight loss, fever, andmental confusion
Other consequences include hypovolemic shock and lossof electrolytes
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Accumulation of fluid in the interstitial space, leading
tissue swelling, caused by anything that increases fluidflow out of the bloodstream or hinders its return
Factors that accelerate fluid loss include:Hypertension, increased capillary permeability, incompetent venous
valves, localized blood vessel blockage, congestive heart failure
EdEdema
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EdemaEdema
Decreased fluid return usually reflects an imbalance incolloid osmotic pressures across capillary membranes
Hypoproteinemia low levels of plasma proteins, may result from protein
malnutrition, liver disease, or glomerulonephritis
Fluids are forced out of capillary beds at the arterial ends by blood pressure, b
fail to return at the venous ends and interstitium becomes congested with fluid
Edema - lymphedemaEdema - lymphedema
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y py p
Blocked (or surgically removed) lymph vessels may resu
in the accumulation of plasma proteins in interstitial fluid
Interstitial colloid osmotic pressure increases,
fluid leaves blood and moves into tissue
Interstitial fluid accumulation could result in a
decrease in blood volume, blood pressure, and
impaired circulation
Protein DeficienciesProtein Deficiencies
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Kwashiorkor - a form of malnutrition caused by inadequate prote
intake and consequent reduced albumin in the blood
hypoalbuminemia and reduced plasma oncotic pressure promote
extravasation of fluid from the plasma into the peritoneal cavity
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:Signs of Hypervolemia:Signs of Hypervolemia
Hypertension
Polyuria
Peripheral edema
Wet lung
Jugular vein engorgement
Especially when hypo-
albuminemia
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:Signs of Hypovolemia:Signs of Hypovolemia
Diminished skin turgor Dry oral mucus membrane Oliguria
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:Clinical Diagnosis of Hypovolemia:Clinical Diagnosis of Hypovolemia
Thorough history taking: poor intake, GI
bleedingetc BUN : Creatinine > 20 : 1
- BUN: hyperalimentation, glucocorticoidtherapy, UGI bleeding Increased specific gravity Increased hematocrit
Electrolytes imbalance Acid-base disorder
Clinical parameters for evaluation ofClinical parameters for evaluation of
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Clinical parameters for evaluation ofClinical parameters for evaluation of
water balancewater balance
CVPPulsePeripheral VeinsWeight
Thirst Intake and OutputSkinEdema
Lab Values
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Reasons for fluid therapyReasons for fluid therapy
Preserve oxygen delivery to tissuesPreserve oxygen delivery to tissues Correct hypovolaemiaCorrect hypovolaemia
Maintain cardiac outputMaintain cardiac output
Optimise gas exchangeOptimise gas exchange
Replace electrolytes & waterReplace electrolytes & water
Maintain urine outputMaintain urine output
Colloids + RBCs
Crystalloids
Identify what is the goal
Choose fluid which best achieves the goal
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Methods of Estimating Maintenance FluidMethods of Estimating Maintenance Fluid
Methods of estimating basal or maintenance fluidrequirements Basal Surface Area
Need to know height and weight, requires table, does not allow
for deviations from normal activity Basal or Calorie Expenditure Method
Requires a table, involves calculations, permits correction forchanges in activity or injury, drier
Holliday-Segar SystemEasy to remember, does not require table or difficult
calculations, does not allow for deviations from normal activity
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:Crystalloids:Crystalloids
Isotonic crystalloids
- Lactated Ringers, 0.9% NaCl
- only 25% remain intravascularly Hypertonic saline solutions
- 3% NaCl Hypotonic solutions
- D5W, 0.45% NaCl
- less than 10% remain intra-
vascularly, inadequate for fluid
resuscitation
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:Colloid Solutions:Colloid Solutions
Contain high molecular weight
substancesdo not readily migrate across
capillary walls
Preparations
- Albumin: 5%, 25%
- Dextran
- Gelifundol
- Haes-steril 10%
Common parenteral fluid therapyCommon parenteral fluid therapy
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D5WD5W
3101541545006%6%
HetastarchHetastarch
330130-160
2.5
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