11. Body Fluid Compartments Flashcards by Priyanka Barad

what is the 60-40-20 rule

60% of body weight = Total Body Weight (TBW)

40% of weight (or 2/3 TBW) = Intracellular fluid compartment (ICF)

20% of weight (or 1/3 TBW) = Extra__cellular fluid compartment (ECF)

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what two compartments make up the ECF

plasma = 1/4 *ECF

intestitial fluid = 3/4 *ECF

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which compartment can be acted on directly to control vol & composition

plasma

–> then interstital fluid will be regulated too

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How do the numbers of fluid intake compare to fluid loss

should match!

total intake = 2300

total loss should be 2300 too (out of this urine is biggest contributer =1400)

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what happens to fluid intake and loss during exercise

increase loss of fluid bc of sweat

reduced urine output

output increases ALOT

-so you need to hydrate to match what you lost!!

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what is third spacing

third space is apart of ECF, usually minimal fluid there

but too much fluid shift from blood vessels (intravascular) into nonfxnal area => fluid trapped

-ascites, interstitial area around lungs –> pul edema, burn pts, liver disease

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what is selectivity

fluid compartments are semipermeable

so using osmosis, h2o moves from high [h2o] to low

trying to match dilution / [solute]

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what is the ionic and nonelectrolyte composition of ICF

K+, Mg2+

proteins and organic phosphates

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what is the ionic & nonelectrolyte distribution in ECF & how is it divded btn the 2 compartments

Na+, Cl-, & HCO3-

plasma: whats above plus proteins

interstital fluid: whats above but lower than whats in plasma

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why is regulation of ECF important

helps regulate BP

maintain via salt balance; so osmolarity is closely regulated to prevent swelling/shrinking of cell

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compare the electrolyte composition of ECF & ICF

ICF: proteins that cant permeate, PO₄^3-, primary cation = K+

ECF: Cl-, HCO3-, primary cation = Na+

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what are nonelectrolytes

molecules w/ covalent bonds that prevent them from dissociating in sol’n

no electrical charge

=glu, lipids, urea

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what are electrolytes

dissociate into ions in water –> gives them higher osmatic power than nonelectrolytes

NaCl, MgCl₂, etc

greater ability to cause fluid shift

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what is osmolality vs osmolarity

osmolality = osmotically active particles per kg of h2o

osmolarity = osmotically active particle per L of total soln

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what are the normal ranges for

HCO3-

albumin

glu (fasting)

serum osmolality

Na = 135-147

K = 3.5 - 5.0

HCO3- = 22-28

albumin = 3.5 - 5.5

glu (fasting) = 70-110

serum osmolality = 285 - 295

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what are the 4 mechanisms that can cause polyuria

increase intake (stress/anxiety, DI)
increased GFR (hyperthyroid, fever)
increased output of solutes (DM, hyperthyroid, hyperparathyroid)
inabilty of kidney to reabs in DCT (CRF, drugs)

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what can cause oliguria

dehydration, blood loss, diarrhea, kidney disease, enlarged prostate

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what can cause anuria

kidney failure, obstruction (stone or tumor)

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what is the difference btn water diuresis & solute diuresis

both = increase h2o excretion

water diuresis = W/O increased salt excretion

solute (osmotic) = WITH increased salt excretion

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what is free water clearance,

how do you calculate & what do the results mean

C_h2o= rate at which solute free h2o excreted

if positive = dilute urine

if negative = concentrated urine, conserving h2o

(if urine osm > plasma osm, free water clearance = neg bc h2o conserved)

how do you measure the amount of fluid in compartments

= dilution method

dye distributed in body fluid compartment based on characteristics
allow dye to equilibrate
remove plasma & meaure [marker]
calculate -> vol of distribution = amount injected/ [] in plasma

amount injected = amoutn injected - amount excreted in urine!

what are the indicators used for each compartment

TBW = isotopic water (d2o, ³h2o, ²h2o, antipyrine)

ECF = mannitol, inulin, sulfate, ²²Na

plasma = ¹²⁵I-albumin, evans blue dye

ICF & interstitial fluid cant be directly measured

how do you measure plasma (serum) osm

normal = 285-295

& estimating way = 2 * [plasma Na]

what is the Gibbs-Donnan Effect

plasma contain proteins (-) = impermeable so they create oncotic gradient && create electrival environment

both favoring movement of h2o INTO cell

what happens if gibb-donnan effect isn't countered

cell swell --\> death prevent this by Na/K ATPase - 3 Na in & 2 K out ==\> prevent excess inward h2o

what forces play a role in h2o movement btn ICF & ECF how does the movement occur

osmotic forces -h2o diffuse thru capillary walls & P diff btn inside & outside vessel help fluid move freely

what are the Ps close to the arteriole & venule ends of the caps & what do the promote

_arteriole end_ - cap BP \> plasma colloid osmotic P ==\> _filtration_ _venule end_ - cap BP \< plasma colloid osmotic P ==\> _absorption_ occationaly extra fluid out of cap and into lymphatic vessels

what are two causes that lead to edema

- change in hemodynamic --\> increase filtration - noticed when interstitial vol increased by 2.5-3 L (ie CHF, liver failure) - renal retention of dietary Na & h2o expansion of ECF vol (ie primary renal disease)

what is an isotonic cell environment & what happens to the cell

environment has [NaCl] = 0.85% equal movement of h2o in & out cell

what happens to a cell in a hypertonic enviornment

[NaCl] \> 0.85% net movemnt out of the cell --\> cell will shrink

what happens to a cell in a hypotonic environment

[NaCl] \< 0.85% net movement of h2o into cell --\> cell swells

How can plasma content change?

- ECF vol los --\> increase [plasma protein] - concentrated - ECF vol gain --\> decrease [plasma protein] -dilute

what will increase Hct

ECF vol loss - concentrated ICF vol gain - swelling of RBC

what leads to decreased Hct

ECF vol gain - dilute ICF vol loss - shrinkage of RBC

what are crystalloids

used in replacement therapy contain organic/inorganic salts dissolved in sterile h2o --\> DO NOT cross plasma mem & stay in ECF use glucose & NaCl (ie 0.9% NaCl normal saline & lactated Ringers (LR))

what are colloids

used in replacement therapy -contain large molecules that don't pass thru semipermeable mem --\> stay in intravascular compartment so fluid out of extravascular space to balance out ie hydroxyethyl startches & albumin

what happens when you have increased fluid loss? hemorrhage vomitting, diarrhea

loss of isosmotic fluid -decrease ECF vol NOT osm bc fluid lost = isosmotic --\> so no need to change ICF vol

what happens to ECV & ICV with water deprivation (increased sweating & no intake)

sweat = hypotonic soln compared to ECF ECF vol decrease & osm increases --\> which cause h2o shift from ICF into ECF until ICF osm increases & is = to ECF osm new steady state --\> ECF & ICF vol decreased & osm increased

what happens to ECF & ICF in hyponatremia

serum Na \< 130-135 decrease ECF osmotic P --\> h2o moved into cell --\> hypovolemia & cellular swelling -increase ICF vol can cause edema, brain cell swelling, irritablility, depression, confusion, weakness, M cramps, anorexia, nausea & diarrhea

what happens with hypernatremia

serum Na \> 147-150 h2o moves from ICF to ECF --\> intracell dehyrdation & shinkage increased ECF vol --\> edema & increased BP high Na levels - M weakness, hyperactive reflexes decreased ICF - thirst, decrease urine output, confusion and ultimately coma

what is the difference btn vol contraction vs expansion

contraction - decreased ECF fluid --\> cause decrease blood vol & BP expansion = increased ECF fluid --\> increase BP & cause edema

what occurs when you have hypotonic fluid loss? dehydration, DI & alcoholism

= hyperosmotic vol contraction decrease ECF & ICF vol & increase osm for both

what happens to ECF & ICF in adrenal insufficiency

=hyposmotic volume contraction -excess NaCl in urine --\> ECF osm decrease --\> cause osm difference & h2o move from ECF to ICF until osm match ICF vol increased & osm decreased

what happens during isotonic vol expansion

ie infusion of isotonic NaCl ECF vol increase (nothing else)

what occurs w/ hypertonic vol expansion

high NaCl intake increase ECF vol --\> increase ECF osm - flow ICF to ECF decrease ICF vol & increase osm

what happens in pts w/ SIADH

(similar effects for excess water drinking) = hyposmotic vol expansion increase ECF & ICF vol & decrease both osm

Pts w/ CHF have low effective circulating vol bc decreased CO. What occurs to counteract this

1. activation of RAAS 2. stimulation of sym NS bc baroreceptor detect decrease P 3. increase ADH secretion 4. increase renal fluid retention --\> edema, retain Na, increase ECF vol but dont correct effective circulating vol

what happens if ECF vol is expanded

renal NaCL & h2o excretion increased | (opposite if ECF vol contracted)

when vascular & body fluid dynamics change, what systems are called into play

renal sym Ns (decrease NaCl excretion) RAAS (decrease NaCl excretion) ADH (decrease h2o excretion) ANP/BNP/urodilatin _(incease NaCl excretion & reduce renin & ADH secretion)_