1 Intro to Renal Physio; Bodily Fluids

Question 1

What is an Eq?

Answer 1

1 mole/valence
—for monovalent 1 Eq = 1 mole
—for divalent 2 Eq = 1 mole, etc.

Question 2

molarity vs. molality

Answer 2

molarity = # moles / L sol’n (M)
molality = # moles / kg sol’n (m)
—diff only important for soln’s with solids (e.g. plasma)

Question 3

osmolality

Answer 3

sum of total number of particles in sol’n; think about ionic compounds: 0.5m Na+Cl- = 1m C6H12O6

Question 4

1 osmole (unit)

Answer 4

amt of a substance that exerts the osmotic P = to 1 mole of non-interacting particles
—takes osmotic co-efficient into account (φ): takes into account interactions between ions that may actually decrease net osmolality (e.g. some Na+ Cl- —> NaCl)

Question 5

colloid/oncotic P

Answer 5

P due to proteins

Question 6

reflection coeff

Answer 6

100% means no solute gets through lumen of blood vessel to other side

Question 7

Donnan effect

Answer 7

q can ∆ osmotic P to be higher or lower than expected

Question 8

What percent of BW is water? What factors ∆ it?

Answer 8

total body water (TBW) = 45-70% of body wt.
—∆s with SKM which has more water (males tend to have more SKM so TBW tends to be higher % of body wt.)
MALES —> 60% BW is water
FEMALES —> 50% BW is water

—Newborns have incr ECFV so have even higher %of BW given by water (~72%)

Question 9

What is the easy 60-40-20 rule?

Answer 9

Assumes TBW is 60% of body wt.
—therefore ICFV = 40% of BW
—and ECFV = 20% of BW

Question 10

What is the breakdown of ECFV?

Answer 10

75% - ISF
20% - PV
5% - other (e.g. CSF, synovial, pleural, peritoneal, aqueous humor)

Question 11

What is the more accurate 60-40-20 rule?

Answer 11

*require remembering that females are 50% water by wt and males 60%
—60% of body water is ICFV
—40% of body water is ECFV
—20% of ECFV is plasma vol.

Question 12

What is the dominant cation in the ICF?

Answer 12

K+

Question 13

What is the dom cation in the ECF?

Answer 13

Na+

Question 14

What is the dom cation in the ISF? Anions?

Answer 14

Na+

—have incr. Cl- and HCO3- due to no neg proteins

Question 15

Is oncotic pressure higher in capillaries of ISF?

Answer 15

capillaries

Question 16

What is normal plasma osmolality?

Answer 16

~290mOsm/kgH2O

Question 17

effective osmolality

Answer 17

estimate that ignores proteins vol and osmotic coeff

—osmolality ~= 2X [Na+]plasma
—b/c plasma osm. is 95% due to Na+ plus its related anions

Question 18

calculated osmolality

Answer 18

more accurate

—osmolality ~= 2[Na+] + [glucose]/18 + [BUN]/2.8

Question 19

osmolar gap

Answer 19

measured - calculated osmolality

—increased in poisoning

Question 20

How does pure H2O distribute between compartments?

Answer 20

heads to all evenly

Question 21

How will ingestion of salt shift fluids between compartments?

Answer 21

Na will shift ISF —> ECF increasing ECFV

—due to low Na+ perm and Na+/K+ ATPase

Question 22

How will salt ingestion ∆ hematocrit?

Answer 22

it will decrease it b/c it will pull water into PV from ICFV diluting [RBC]

Question 23

How will salt ingestion ∆ oncotic pressure?

Answer 23

it will decrease

b/c it will pull water into PV from ICFV diluting [protein]

Question 24

What is the ultrafiltration pressure?

Answer 24

sum of oncotic and hydrostatic pressure (opposite directions in capillaries)

Question 25

describe how the filtration coefficient changes

Answer 25

Kf ∆s depending on where you are in the body: brain is low; kidney is very high

—∆s in response to vasoactive hormones/cytokines

Question 26

How does reflection coeff ∆ throughout the body?

Answer 26

really high in glomeruli (almost 100%—no proteinuria)
—really low in liver sinusodes

—∆s in response to vasoactive hormones/cytokines

Question 27

What IV sol’n would you use to replace an ICFV deficit?

Answer 27

a hypotonic sol’n e.g. 0.45% NaCl OR isosmotic glucose (b/c glucose will be metab’d and then it’s just like pure water)

Question 28

What IV sol’n would you use to decrease ICFV?

Answer 28

a hypertonic soln’ e.g. 10% mannitol or 3% NaCl

Question 29

What % of NS stays in the plasma?

Answer 29

only ~25%

—re-call that ECFV is 75% ISF and ~20-25% PV

Question 30

Give some examples of colloid IV sol’ns. What are they used for?

Answer 30

colloids are “plasma expanders” b/c the blood vessels are impermable to them
—examples include: Colloids include 5% albumin, and various gelatins, dextrans and starches.

Question 31

What is basic idea behind ORT?

Answer 31

safer/cheaper than IV rehydration

—give water with salt AND sugar b/c Na+ is absorbed in cotrans with glucose)

Question 32

What happens If capillary pressure significantly exceeds the oncotic pressure?

Answer 32

edema

Question 33

What fluid shift happens if capillary pressure declines?

Answer 33

auto-transfusion