Body Fluid Compartments Flashcards
what is the normal osmolality that we should look for
290 mOsm
how do you calculate total body water TBW
0.6*BW(body weight)
what is the third space
transcellular compartment or locations that the body should not have water
how do you calculate ICF or intracellular fluid
0.4*body weight OR 2/3 of TBW(total body water)
how do you calculate ECF or extracellular fluid
0.2*BW or 1/3 of TBW
how do you calculate interstitial fluid
0.75*ECF
how do you calculate plasma volume
0.25*ECF
How do you calculate venous volume
0.8*plasma volume
how do you calculate ECV or effective circulating volume
0.2*plasma volume
what age group has the highest percentage of TBW
infants and this goes down with age
where do we gain water input
drinking, food, and carb metab
where do we lose water
feces, sweating, insensible perspiration, and urine
what are our main extracellular ions
Na and Cl
what are our main intracellular ions
K
where are protein levels highest
in ICF and vascular compartments
what are the main proteins we are concerned with
albumin and globulins
what can be used to help measure plasma volume?
albumin that is radiolabeled
what can’t we measure directly
ICF and ISF
how do we measure TBW experimentally
heavy water or antipyrine
how do we measure ECF experimentally
heavy Na, l-iothalamate, thiosulfate, inulin
what is the gibbs donnan effect
the negative charge of proteins within the vasculature causes the Na+ and K+ concentrations to be slightly higher than expected
what is ECF osmolality driven by
Na
where is the most Na found
vasc>interstitium>ICF due to action of NaK ATPase
what does a disrupted NaK pump cause an increase in
ICF [Na] this causes cellular swelling
what is ICF osmolality driven by
K
what are the two ways to estimate plasma osmolality
2*[Na]
2*[Na] + glucose/18 + urea/2.8
the ECF and ICF are highly permeable to what
water but NOT electrolytes
the capillary membrane is highly permeable to what
small ions which drive the starling forces
what main force favors filtration? opposes filtration
Pc; Pi_c
what are some common causes that increase Pc
- increased arterial pressure
- increased venous pressure
- decreased precapillary resistance
- increased postcapillary resistance
almost all capillaries have a precapillary resistance > postcapilllary resistance except for
glomerular
what decreases Pc
- decreased arterial pressure
- decreased venous pressure
- increased precapillary pressure
- decreased postcapillary pressure
how are hepatic capillaries different than renal capillaries
hepatic are highly permeable to proteins and Pi_c plays a little role in fluid exchange for them
what is the full formula for capillary filtration
Kf [(Pc-Pi)-(Pi_c-Pi_i)]
what does Kf stand for in capillary filtration
permeability coefficient
ECF ___________ controls ICF volume
osmolality
what are some general factors to think of when looking at changes in ECF and ICF
- All solutes and water that enter or leave the body do so via ECF.
- ICF and ECF are in osmotic equilibrium.
- Equilibration occurs primarily by shifts of water, not solutes.
what are some factors that affect ECF/ICF
- water ingestion
- dehydration
- IV infusions
- diarrhea or vom
- sweating
- diuresis
- disease (IBS, DM, hypoaldosteronism, SIADH)
what changes does excessive intake of NaCl and hyperaldosteronism cause to fluid levels
increased ECF, which decreases ICF and increased ECF mOsm and ICF mOsm
what changes does water gain cause to fluid levels
increased ECF and ICF, decreased ECF and ICF mOsmq
what changes does dehydration cause to fluid levels
decreased ECF and ICF, and increased ECF mOsm and ICF mOsm
what change does NaCl loss (adrenal insufficiency) cause to fluid levels
increased ICF; decreased ECF, ECF mOsm, ICF mOsm
what are the ranges we define as hyper natremia and hyponatremia
plasma >146 mEq/L
plasma < 136 mEq/L
what changes do we see in the darrow yannet diagrams for fluid retention? excretion
fatter and shorter
narrower and taller
what type of IV fluids can stay in the ECF or distribute depending on composition? which stay in the vascular space?
crystalloid fluids (normal saline, lactated Ringers); dextran or albumin
isoosmotic or isotonic solutions have the same osmolatlity as _____
the ECF
hyperosmotic or hypertonic solutions have an osmality (higher/lower) than the ECF
higher
hypoosmotic or hypotonic solutions have an osmality (higher/lower) than the ECF
lower
adding a isoosmotic solution changes what
only the volume in the ECF
adding hyperosmotic solutions do what
increases Osm in the ECF which decreased ICF and increased ECF
what do hyposomotic solution do
when added to ECF, Osm decreased and water moves out of the ECF and into the ICF to equilibrate which causes both ICF and ECF volumes to increase
what would you administer to dilute the ECF and rehydrate cells
hypotonic solution
what would you administer to replace fluid loss and expand intravascular volume
isotonic solution
what would you give to treat severe hyponatremia
hypertonic solution
what happens in CHF that exacerbates the edema issue
Pc is already increased so edema occurs, kidneys hold onto more water to increased vascular volume, this causes more edema
what happens to fluid levels in renal disease
Na and H2O are inappropriately retained which causes an increase in Pc and edema results
what causes edema in liver disease, malnutrition, and nephrotic syndrome
decreases in Pi_c because protein synthesis is affected
