Fluid compartments Flashcards
how much percent of our body is water
60%
how is water divided in ECF and ICF
ECF is 1/3
ICF is 2/3
the plasma is considered ECF or ICF
ECF
What is in the “third space” when there is excess fluid
water from epithelial secretions, synovial and CSF
what percent of ECF is plasma
1/4
how many liters are in the Arterial effective circulating volume
.7 liters
What is the effective circulating volume independent of
extracell volume, plasma volume and CO
What is Vd of a drug
the colume of body fluid in which the total dose is distributed at same concentration of plasma
if the Vd is 45
45 all body tissues, even bone and spinal fluid
how does daily total intake and output of fluid compare
in the end equal each other.
Compare Na, K, Ca, Mg and HCO3 and HPO4 in ICF vs ECF
ECF has higher Na and Cl and HCO3-
ICF has higher K, Mg and HPO4
How is the osmolarity in ECF vs ICF
the same osmolarity
where are there higher non-electrolyte protein levels
ICF, intravascular compartments
do the proteins change osmolarity? oncotic pressure?
changes oncotic pressure
does not change osmolarity because the large proteins are impermeable
majority of the non-electrolytes in the plasma are what 2 compounds
phospholipids and cholesterol
how do we measure total body water and plasma volume directly, clinically
dilution of injected radioactive substances or dyes
how is ICF fluid calculated
TBW-ECF
how is interstitial volume calculated
ECF- plasma volume
how can total blood volume be calculated
need to know plasma volume and Hct
TBV= plasma volume/1-Hct
how can you estimate plasma osmolality by [Na]
2X plasma [Na]
What is the donnan effect
Na K concentrations are higher in vascular spaces due to the negative charges of proteins
what besides [Na] is important in plasma osmolality
glucose/18 and urea/2.8
What keeps the Na concentration what it is
Na-K ATPase pump
what ion is the key regulater of intracellular osmolality
presence of K
fluid distribution between ECF and ICF depends on what
osmotic effects of Na and Cl
What is the capillary cell membrane between ECT and capillary permeable to
small ions
what is the fluid distribution dependent on between capillary and interstitial fluid
starling forces
What scenarios clinically result from fluid/solute loss
Bruns, Hemorrhage, vomiting/diarrhea, dehydration
what do you target during intravenous replacement fluids when oral rehydration is not suitable
target the volume-depleted comparment
what is in crystalloid fluids
contain varying concentrations of electrolytes and can stay in ECF or be widely distributed depending on composition
what are types of crystalloid fluids
normal saline, lactated Ringer’s solutions
what is in colloid fluids
large proteins and molecules that stay in vascular space
why do we give colloid fluids
to pull volume out of cells
a isosmotic solution means what
solutions that have the same osmolarity as the ECF
does not change osmolarity, increases volume only
a hyperosmotic solution means what
solutions have an osmolarity greater than that of the ECF
What will happen in the addition of a hyper osmotic solution
when added to the ECF, osmolarity increases and causes water to move from cells to ECF to increase volume
a hyposmotic solution means what
solutions having an osmolarity less than that of ECF
what happens in the addition of a hyposmotic solution
decreases the osmolarity and water moves into the cells
Increases both ECF and ICF
What does tonicity of a solution depend on
the concentration of impermeant solutes in ECF vs ICF
how does cell volume change when in an hypotonic solution? hypertonic? isotonic?
in hypotonic the cell V increases
in hypertonic the cell V decreases
isotonic- the cell V does not change
What factors affect osmolarity and V of ECF and ICF
water ingestion, dehydration, intravenous infusions, diarrhea or vomiting, sweating, diuresis, disease
what factor affects distribution of fluid between ECF and ICF compartments
ion distribution Na ATPase actvity(keeps Na low and K high intracell)
what factos affect distribution of ECF between plasma and interstitial comparments
balance of hydrostatic vs oncotic pressure
intravascular pressure in capillaries vs plasma protein and solute concentration
palpable swelling is from what
expansion of interstitial fluid volume
renal retention of dietary Na and water how does ECF change
increases
At what levels is edema apparent
2.5-3 L aboe normal plasma volume of 3L
what usually causes edema
compensatory renal retention of Na and water to maintain plasma volume
what clinical situations result in edema
primary renal disease like glomerulonephritis and nephrotic syndrome
what causes non-pitting edema
swollen cells due to increased ICF volume
how is edema usually treated
diuretics
how is osmotic pressure determined
by the number of solutes in a solution, not size or mass or chemical nature
what is the difference between osmolarity and osmolality
osmolarity is the number of solutes per L of solvent
osmolality is the number of solute per 1 kg of solvent
What factor is osmolality independent of
temperature
if you placed a RBC in a solution of urea what would happen
the RBC would burst because urea is hypotonic
would urea be condisered and effective or ineffective osmole when talking about RBC membrane
ineeffective because it cannot exert an osmotic pressure since it can cross the membrane
What is oncotic P
osmotic P generated by large molecules (proteins) in solution
what is specific gravity
the total solute concentration in a solution
What do we measure clinically to assess the concentrating ability or the urine
the specific gravity
What makes of ECF
1/4 plasma
3/4 interstitial fluid from bone, dense CT and CSF
Ascites is an example of what fluid utilization
“third space”
how is urea measure in plasma
as the nitrogen in the urea molecule. BUN
does hydrostatic pressure cause a gradeint across ECF and ICF? osmotic pressure?
hydrostatic pressure does not
osmotic pressure does
what does the capillary filtration coefficient reflect of capillary wall? Kf
the movement of fluid and SA available for filtration
Precapillary sphincters control what
hydrostatic P in an individual capillary and number of perfused capillaries in tissue
What is used clinically to decrease a cerebral edema
mannitol because it does not cross blood brain barrier and sucks water out, effective osmole
if you need to increase a patients vascular volume what do you infuse
5% albumin because albumin does not cross barrier
how do you expans a patients ECF
isotonic NaCl solution
what are the neural and hormonal effector mechanisms to changes in volume and osmolarity of blood
neural is sympathetic discharge
hormonal is ADH and aldosterone secretion
where are the osmoreceptors of the body located
anterior hypothalamus near supraoptic nuclei
what do osmoreceptors not respond to
hypertonic solutions of urea or glucose
where are the volume receptors of the body located
right atrium
an increase in blood volume has what effect
stimulate volume receptors that inhibit vasomotor area and suppress sympathetic discharge
also inhibit thirst and ADH secretion
which type of receptor in the body is more sensitive. osmo or volume?
which has greater effects?
osmoreceptors more senstiive
volume receptors have stronger effects
Where is ADH released and what is its role
posterior pituitary gland to promote water reabsorption from collecting duct to make isotonic or hypertonic
What stimulates the release of aldosterone
circulating ANG II from SANS activity
rise in plasma [K]
fall in plasma [Na]
What is the effect of aldosterone
reabsorption of Na from distal convoluted tubule
What stimulates thirst? inhibits?
stimulated by osmoReceptor impulses and ANG II
inhibited by volume receptor stimulation
What are the two major responses to hypovolemia
salt cravings and sympathetic discharge to retain Na and H2O
What are the consequences to a lot of drinking plain water
increase ICF and ECF volumes with slightly lower osmolarity
What is the response to drinking mass amounts of plain water
excretion of hypotonic urine. however Na always gets out so long term leads to Na depletion
what is the consequence of drinking excess salt, hypertonic saline
plasma volume and osmolarity increase. the plasma colloid pressure decreases. so water moves out of capillaries increasing ECF volume and osmolarity. this extracts fluid from ICF (shrinking cells)
what is the corrective response to intake of hypertonic saline
water retention because increase of plasma osmolarity. plasma volume overload overrides this osmolarity tonicity.
suppress thirst and ADH, excretion large volumes hypotonic urine..exacerbating osmolarity
Natriuretic hormone that promotes Na excretion
sweating is creating what type of tonicity
loss of hypotonic fluids
diarrhea, intestinal obstruction, ascites, burns, hemorrhage is creating what type of tonicity
loss of isotonic fluids
what is the consequence of profuse sweating or diarrhea or hemorrhage
ECF V decreases(plasma is ok because proteins retain fluid)
ECF osmolarity increases(unless loss isotonic)
Rise in ECF osmolarity draws water from cells, Shrunk cells–> painful cramps
what is the corrective response to losing hypotonic solution
stimulation of osmoR because plasma osmolarity increased, redicution of the plasma volume inhibits volume R.
need to re-correct with isotonic or hypotonic SALT solutions
Na restricted diet or loss of hypertonic fluid from vomititng causes what
decrease in ECF osmolarity, water moves into cells
ECF V dec, ICF V increases- cell swell
thirst center swells and interprets as excess water so inhibits thirst
what is the corrective response to loss of hypertonic solution
thirst is absent, which is good so cells don’t burst
intense Na craving to draw water out from ICF back into ECF
as cells lose water thirst is restored and fluid intake corrects the rest
