02 Body Compartments

8/8/2019 02 Body Compartments

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ody Compartmentsody CompartmentsPhysiology

-Dr. Tiara Calvo


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Fluid Compartments% of Body Weight Fraction of TBWTotal Body water 60 1.0

Intracellular fluidvolume

40 2/3

Extracellular fluidvolume

20 1/3

Plasma 5 1/12 (1/4 of ECF)

Interstitial fluid 15 (3/4 of ECF)


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Fluid CompartmentsMarkers used tomeasure volume

Primary cation andanion

Total Body water Tritiated H2O, D2O none

Intracellular fluidvolume

TBW ECF (indirectmeasure)

C: K A: Organic

phosphate, proteinsExtracellular fluidvolume

Inulin, Mannitol C: NaA: Cl, HCO3

Plasma RISA, Evans blue C: NaA: Cl, HCO3, Plasma

proteinsInterstitial fluid

ECF-plasma volume(indirect measure)

C: NaA: Cl, HCO3


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Total Body WaterICF: 2/3 of TBWECF: 1/3 of TBW

ISF: 2/3 of ECF

:CO Cardiac Output


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Intracellular volume~40% of body weight (~25 L)

ECF Volume~20% of body weight (~15 L)

The 60, 40, 20 rule for body fluid volumes

Total body water ~60% of body weight (~40 L)


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ICF vrs ECF The two compartmentsare separated be thecell membranes.

Have two maincharacteristics:

Freely permeablewater

Impermeable tosodium chloride


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Plasma osmolalityPOsm: is the number of solutes in plasma(tonicity of plasma)

Plasma osmolality (mOsm/kg) =2([Na+] + [K+]) + ([BUN]/2.8) + ([Glucose]/18)

POsm approximates serum [Na]Urea shifts through ICF and ECF freely so it will

not cause any movement of H2O


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Changes in RBC volumes300 lower mOsm: cell swells300 higher mOsm: cell shrinks

300 same mOsm: no change

Examples:A- 400 mOsm NaCl?

B- 200 mOsm NaCl?C- 300 mOsm NaClD- 150 mM Nacl?


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sotonic fluid sotonic fluiddisordersisorders
http://en.wikibooks.org/wiki/File:Osmosis-_red_cell_in_isotonic_soliution.JPG


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Isotonic Loss:

equal loss of Na & H2O= Body OsmSerum Na Normal:

TBNa / TBW

No Osm gradientECF contracts= ICF

CO due to decreaseof plasma vol

Ej. Adult Diarrhea,Vomiting,Hemorrhage, isotonicurine


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Isotonic Gain:

equal gain of Na & H2O= Body OsmNl serum Na: TBNa /

TBW

No Osm gradientECF expanded= ICF

CO

Ej. Excessive isotonicfluid or normal saline


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0.9% Normal salineIsotonic crystalline solutionApproximates plasma tonicity

Used to:maintain BP in volume loss conditionsbleeding

To replace isotonic loss of fluid

diarrhea


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ypotonic fluid ypotonic fluid

disordersisorders1- Always due to hyponatremia2- Osmotic gradient: H2O shifts into ICFcompartments (expands)
http://en.wikibooks.org/wiki/File:Osmosis-_red_cell_in_hypotonic_soliution.JPG


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Loss Salt: more loss of salt than H2O hyponatremia

serum Na Body Osm

TBNa / TBWECF contracted

COICF expanded

Ej. Loop Diuretics,Addisons disease,21-OHase deficiency


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ypo a + a n ureH2O:

with no gain of Na Body Osm TBNa / TBWIncrease plasma volume

due to:ECF expandedICF expanded

CO

Ej: Syndrome of inappropiate secretionof ADH (Rx H2Orestriction)


19/31


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HypoNa + Hypotonic

Gain of Salt Body Osm TBNa / TBW

ECF expanded CO :Sterlings force

alterICF expanded

Ej. Congestive heartfailure, Cirrhosis,Nephrotic Syndrome


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Pitting EdemaGain a little more of H2O than Na

hyponatremia pitting edema states

(transudates).NOTE: always when there is an TBNa it will

cause pitting edema.


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ypertonic fluid ypertonic fluid

disordersisorders1- due to hypernatremia or hyperglycemia2- Osmotic gradient: H2O shifts out of ICF (contracts)
http://en.wikibooks.org/wiki/File:Osmosis-_red_blood_cell_in_hypertonic_soliution.JPG


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yper a + ypo on cLoss of Salt:

loss more H2O than salt Body Osm TBNa / TBW

ECF contractedICF contracted

Decrease of plasmavolume

CO

Ej. Osmotic diuretics(glucose), Sweating,Infant diarrhea


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Hypotonic Loss of SaltInfant diarrhea loss of H2O causinghyponatremia if given pure H2O, it willlower the serum Na more Rx Pedialyte(hypotonic salt solutions) they have glucoseor galactose to Na to be reabsorbed in theGIT (cotransport pump).


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HyperNa + Loss of

Pure H2O Body Osm TBNa / TBW

ECF mildcontracted

ICF contractedNl CO (no loss of salt)

Ej. Insensible H2Oloss (fever),Diabetes Insipidus


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Hypertonic Gain of

Salt Body Osm TBNa / TBWECF expandedICF contracted

Increase of plasmavolume

CO

Ej. 3% hypertonicsaline, Na antibiotic,NaHCO3


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Diabetic Ketoacidosis: Body Osm Glucose, serum

Na TBNa / TBW

(dilutional effect ICFH2O)

ECF contracted CO

ICF contractedEj. Osmotic diuresis

02 Body Compartments

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