Review of Renal Phys

Question 1

what is the 60, 40, 20% rule?

Answer 1

total body fluid is 60% of the body weight. Intracellular fluid is 40% of the body weight. Extracellular fluid is 20% of the body weight

Question 2

what happens to total body fluid as you age?

Answer 2

decreases with age from 75% of BW at birth to 50% of BW in old age. ECF decreases from 50% of TBF at birth to 30% of TBF in old age.

Question 3

blood pressure equation

Answer 3

BP = TPR x CO

total peripheral resistance times cardiac output

Question 4

urine output in dehydration and overhydration

Answer 4

dehydration is less than 1.4 liters per day, overhydration is more than 14 liters per day

Question 5

what is the function of the kidney

Answer 5

to maintain constant ECF volume and solute composition by acting upon the enormous volume of glomerular filtrate to form urine

Question 6

how does kidney maintain constant ECF volume?

Answer 6

volume receptors sense changes in pressure and regulate ECF expansion and contraction.

Question 7

what happens when you change the amount of sodium intake

Answer 7

you throw off the sodium balance and it takes the body a few days to readjust

Question 8

what happens when you decrease dietary sodium intake

Answer 8

induces decreased urinary sodium output by adjusting the magnitude of sodium reabsorption until sodium balance is achieved.

Question 9

edema

Answer 9

excess accumulation of fluid in the interstitial space due to cardiac, renal, hepatic, or endocrine dysfunction.

Question 10

what causes edema

Answer 10

imbalance of hydrostatic and oncotic pressures across the capillary wall induces a shift in fluid distribution from the intravascular to the extravascular space, resulting in isotonic retention of sodium and water and decreased circulating volume

Question 11

what does decreased renal perfusion pressure cause?

Answer 11

activation of the renin-angiotensin-aldosterone system, which further increases sodium retention and edema

Question 12

how do diuretics work

Answer 12

forcing increased elimination of sodium and water in urine. this decreases hydrostatic pressure and inreases oncotic pressure, favoring absorption of edematous fluid

Question 13

renal clearance

Answer 13

defined as volume of plasma cleared of a solute per unit time. measured in ml/min.

Question 14

how do you estimate measurement of GFR?

Answer 14

use renal clearance of inulin or creatinine. these do not go through reabsorption or secretion, and therefore the amount excreted is equal to the amount filtered.

Question 15

what percentages are negative or positive water balances?

Answer 15

when the fractional excretion of water is less than 1%, negative water balance. more than 1% is a positive water balance

Question 16

what do alkalosis and acidosis induce?

Answer 16

alkalosis induces potassium secretion, acidosis decreases potassium secretion

Question 17

thick ascending loop of henle

Answer 17

impermeable to water. mediates solute reabsorption in absence of water reabsorption, diluting the tubular fluid. counter current multiplication of solute gradient extends from cortex to papilla. this is where the kidney makes dilute or concentrated urine

Question 18

how is normal ECF volume preserved

Answer 18

achieved by the ability of the kidney to maximize or minimize the osmolarity of the urine in response to ECF volume contraction and expansion

Question 19

ADH and its relationship to ECF and osmolarity

Answer 19

ADH increases when osmolarity increases. ADH increases water permeability of collecting duct, which allows reabsorption of water (negative free water clearance). vice versa for low plasma osmolarity.

Question 20

late distal tubule and collecting duct

Answer 20

sodium reabsorption in the late distal tubule and collecting duct is regulated by circulating levels of aldosterone which varies according to the prevailing sodium balance. sodium reabsorption is coupled to potassium secretion. potassium secretion is regulated by aldosterone.

Question 21

what are diuretics?

Answer 21

drugs which increase the volume and rate of urine output by decreasing active reabsorption of sulutes and/or water in one or more segments of the nephron. they change the volume and ion concentration of the ECF by changing the volume and ion concentration of the urine.

Question 22

therapeutic uses of diuretics

Answer 22

hypertension, edema, calcemia and kalemia

Question 23

effect of the different types of diuretics on concentration and dilution of the urine

Answer 23

loop diuretics decrease capacity of kidney to concentrate and dilute urine in response to decreased and increased water consumption. decrease solute reabsorption in cortical talH and medullary talH. thiazide diuretics decrease the capacity of the kidney to dilute the urine in response to increased water consumption. they decrease solute reabsorption in the early distal tubule.

Question 24

reabsorption of carbonic acid

Answer 24

carbonic anhydrase turns H2CO3 into CO2 and H20, which goes into the cell. here, a different carbonic anhydrase turns it back into H2CO3, which turns into H and HCO3. the H+ is used to make H2CO3 outside of the cell. the HCO3 is reabsorbed.

Question 25

carbonic anhydrase inhibitors

Answer 25

induce a moderate increase in urine volume with increased excretion of sodium, potassium, and bicarb. induce a moderate reduction of ECF volume. Limited use as a diuretic. main complications are acidosis and hypokalemia. accumulation of ammonia in ECF is main toxicity. this increases risk of hepatic encephalopathy and is contraindicated in people with cirrhosis

Question 26

osmotic diuretics

Answer 26

increase rate and volume of urine due to filtration and presence of nonreabsorbable solute in the tubular fluid. increases osmolarity of proximal tubule fluid which opposes the isotonic reabsorption of sodium and water. mannitol is administered IV for increasing clearance of dtugs, minimizing renal failure, decrease ocular and cranial pressure, and in diagnosis of oliguria

Question 27

high ceiling/loop diuretics

Answer 27

most efficacious of diuretics. induces ECF volume contraction and a change in ECF solute concentration. leads to hyperbicarb, hyperuricemia, and increased BUN and creatinine. clinical apps rise from prompt onset of large diuresis. good for crisis episodes of pulmonary edema, good for hypercalcemia, and good for drug tox. complications are hypokalemia, hyponatremia, alkalosis, hyperuricemia, increased BUN and creatinine. ototoxicity if combined with aminoglycoside antibiotics

Question 28

thiazide diuretics

Answer 28

moderate diuresis. induce ECF volume contraction with same effects as loop diuretics, except also hypomagnesemia. main use is to control hypertension. can be used for edema, hypercalciuria, and nephrogenic diabetes insipidus. same complications as loop. decrease capacity of kidney to dilute the urine and compensate for ECF volume expansion

Question 29

potassium sparing diuretics

Answer 29

aldosterone dependent and independent mechanisms. induce a moderate diuresis increasing FE of sodium. increased effect when combined with loop diuretics or thiazide diuretics. modest ECF volume reduction. main use is in combo with other diuretics to minimize potassium depletion while controlling hypertension. other uses are edema, aldosteronism, hypercalciuria, polyuria due to lithium. clinical complications are hyperkalemia and androgen receptor antagonism.

Question 30

drug activity of a diuretic depends on:

Answer 30

plasma concentration, renal blood flow, GFR, tubular secretion, and tubular fluid concentration.

Question 31

what do you do with diuretics in patients with renal failure or nephrotic syndrome?

Answer 31

have to give high doses of diuretics