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8/7/2019 03 Fluids & Electrolytes
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Fluids & Electrolytes(Background Information: Physics)
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5 Considerations5 Considerations
Volume of fluidVolume of fluid
TonicityTonicity
Specific ElectrolytesSpecific Electrolytes
AcidAcid--base balance (impact)base balance (impact) Caloric influenceCaloric influence
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Volume of WaterVolume of Water
2-3 liters/day
1 liter: insensible
Rest: urinary output
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Insensible LossesInsensible Losses
600 mL: respiration
200 mL: feces
200-400mL: perspiration/evaporation thru
skin (little minimum flexibility)
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Urinary output can adjust to a fluid ration short of2-3 liters.Normal dietary intake: 1,200 mOsm
Good kidney: 1,400 mOsm / L
Patient with renal problem: flexibility is lost Ex: chronic renal disease = stage of diuresis
Plasma osmolality vs. kidney's concentrating ability
Maximum water intake: can go beyond the usual 2- 3liters/day
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2 Mechanisms2 MechanismsHypotonicity
Hypothalamus
ADH secretion
Action or lack of action of Aldosterone (Naretention or excretion): water goes with it
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Acute Renal Failure/Terminal ChronicAcute Renal Failure/Terminal Chronic
Renal FailureRenal Failure
endogenous water (oxidation of fats /
metabolism of muscle)
1 cc / 10 cal burned
300 gms loss/day if not eating (fat andmuscle)
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Maintenance FluidMaintenance Fluid
should be scaled down for smaller than
average adults & children
Body surface
a satisfactory indicator of lean tissue mass calculated from height and weight better reflection of the body size
1,500 cc/m2 of body surfaceAverage adult: 1.7 m2 (2 liters/day)
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TonicityTonicity
definition
body fluid
not composed of water alone
different compartments has differentindividual solutes
total number of particles remarkably
constant (300 mOsm/L)
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PlasmaPlasma tonicity mostly attributable to electrolytes (280
mOsm/L) - sodium other half
anions (Chloride and bicarbonate)
modest share crystalloids (CHO, urea, creatinine)
Protein: 2 mOsm
Sodium is responsible for tonicity but not with metabolism(ADH mechanism)
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What happens to the regulation of tonicity ifthe normal supply of solutes (mainly
Sodium) drops down to zero?
in some situations, volume conservationoverrides tonicity regulation
regulation is much easier if Sodium intake ismaintained at somewhat similar to diet (100-150mEq/day)
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To Provide Daily RationTo Provide Daily Ration
different IV fluid choices
water without salt
water with salt
sugar is added to water without saltsolution (5% - roughly isotonic to plasma)
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Specific ElectrolytesSpecific Electrolytes volume and tonicity
Potassium (K+): only one needed to be given daily daily dietary K+ intake: 75 to 100 mEq (KCl, KPO4, K
Acetate)
sudden administration: cardiac arrest (impact on ICU
management) (if sugar is added, safe limit: 10 mEq/hour (max: 20
mEq/hr)
Note: not wise to have >40 mEq/L (catch-up game)Calcium (Ca++), Phosphorus (P), Magnesium (Mg++) = has plenty ofstores
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Time for AdditionTime for Addition
Vit. B
requirement if CHO is the entire caloric supply
Vit. C
peace of mind surgeons (scurvy)
cheap, non-toxic, water soluble
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Acid Base BalanceAcid Base Balance given adequate water and electrolytes, kidney
will take care of acid base balance rather nicely 2 issues has to be raised = basis
proportion of Na+ and Cl- in IV fluids 0.9%NaCl = not exactly the proportion in plasma
Normal individuals / impaired renal function / patients proneto acidosis
balanced solution: better source of Na+
most balanced solutions in the market haveproportions of Na+ and Cl- similar to plasma
complemented by bicarbonate, lactate or acetate
Ringer's lactate (Hartmann's solution) undisputed
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Question: ability of the body tometabolize lactate
pH of the existing IV fluids in the
market
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pH 5 (1000 x more acid than the blood)
Relax: scarcely a drop in the bucket
value gained from volume expansionoutweighs very minor blood buffersexpenditure even so, still ask: why not
make it with more physiological pH*unstable
= neutralizing solution (5 mg Heparin + 0.1
mg Prednisolone/liter bottle)
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Caloric IntakeCaloric Intake 2,500 cal/day (average adult) 1,500 ca/day (completely inactive)
4,000 5,000 cal/day (severe stress / athletes) 0.5 to 1 gram/kg body weight/day = minimum protein requirement IV fluids:50 g glucose /L (4 cal/gram) 200 cal/L (x3)
600 cal/day starvation = converted to semi-starvation modest amount of calories, spare protein breakdown and lose
weight gracefully rather than catastrophic catabolism glucose: tonicity and protein sparer
total parenteral nutrition early start of feeding = cost consideration oral absorption
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Problem Oriented ApproachProblem Oriented Approach Pediatric patients new admission (kidney status)
ward Adult patients with cardiac problems / state of congestion pneumonia patients (SIADH)
electrolyte imbalance Critically ill Sepsis Dengue shock syndrome DIC
Crystalloids Colloid
FLUIDS & ELECTROLYTESFLUIDS & ELECTROLYTES