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Block 9 Week 2 Meg > Duan: Diuretics I > Flashcards

Duan: Diuretics I Flashcards

1
Q

a compact cluster of convoluted capillaries, site of FILTRATION, functioning to remove certain substances from the blood before it flows into the convoluted tubule.

A

glomerulus

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2
Q

List the components of the nephron

A

glomerulus: site of filtration
tubule system: site of reabsorption, secretion, excretion
includes proximal convoluted tubule, Loop of Henle (descending, ascending), distal convoluted tubule, collecting tubule

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3
Q

What is the favoring force in glomerular filtration? What is the opposing force? How do you determine the net filtration pressure?

A

favoring force: capillary blood pressure
opposing force: blood colloid osmotic pressure
NFP = favoring force - opposing force

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4
Q

glomeruli in outer cortex & short loops of Henle that extend only short distance into medulla
blood flow through cortex is rapid
majority (70-80%) of nephrons

A

cortical nephron

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5
Q
  • glomeruli in inner part of cortex & long loops of Henle which extend deeply into medulla.
    – blood flow through vasa recta in medulla is slow
    – medullary interstitial fluid is hyperosmotic
A

juxtamedullary nephron

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6
Q

A two-step process beginning with the active or passive extraction of substances from the tubular fluid into the renal interstitium (the connective tissue that surrounds the nephrons); then these substances are transported from the interstitium into the bloodstream . These transport processes are driven by Starling forces, passive diffusion, and active transport.

A

reabsorption

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7
Q

How does the descending limb of the loop of Henle differ from the ascending limb?

A

descending limb: highly permeable to H20

ascending limb: low permeability to H20 **responsible for 15-50% of reabsorption

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8
Q

This portion of the Loop of Henle allows for the passive and active transport of salts such as Na+ and Cl- to move out of the tubules and be reabsorbed. Also, most K+ in the tubules cycles back into the lumen.

A

thick ascending limb

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9
Q

What is the main function of the Loop of Henle?

A

create a concentration gradient in the medulla of the kidney by means of a countercurrent multiplier system; creates an area of high urea concentration deep in the medulla

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10
Q

Briefly explain the loop of Henle

A

Descending limb: progressively becomes more concentrated as it loses H20

Vasa recta: removes water leaving the loop

Ascending limb: pumps out Na+, K+, and Cl-, so that the filtrate becomes hypoosmotic

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11
Q

What happens to Na and Cl in the distal convoluted tubule? What happens to Ca++?

A

Na and Cl- are reabsorbed from the DCT, creating more dilute urine;
Ca++ is also reabsorbed due to PTH

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12
Q

Two cells of the collecting tubule? Which cells are the site of action of aldosterone? Which cells are involved in acid-base homeostasis?

A

principal cells and intercalated cells

  • *aldosterone works on prinicipal cells to reabsorb Na+
  • *intercalated cells participate in acid-base homeostasis
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13
Q

Increases the activity of both apical Na+ channels and the Na+/K+ ATPase in the collecting duct; increases Na+ reabsorption and K+ secretion

A

aldosterone

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14
Q

controls the water permeability of principal cells in this segment ;
regulates the insertion of aquaporin-2 (AQP2) into principal cells in the apical membrane

A

ADH (vasopressin)

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15
Q

If you have low ADH or absent ADH, what happens to your urine?

A

large volume of hypotonic and dilute urine, because there is low H20 permeability due to insertion of fewer aquaporins

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16
Q

If you increase ADH, what happens to your urine?

A

small volume of hypertonic and concentrated urine because there are more aquaporins and increased H20 permeability

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17
Q

How do you calculate the amount of solute excreted in the urine?

A

Amount filtered + amount secreted - total reabsorbed

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18
Q

This is a carbonic anhydrase inhibitor

A

Acetozolamide

**all end in -amide

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19
Q

How do carbonic anhydrase inhibitors work?

A

inhibit apical and cytosolic carbonic anydrase, thus increase HCO3- excretion
increase Na+, K+, and H20
**results in alkaline urine
causes metabolic acidosis as HCO3- levels drop

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20
Q

When are carbonic anhydrase inhibitors used as non-diuretics clinically?

A

A FAMILY GAME
Alkalinizing urine for excretion of weak acids
Familial hypokalemic periodic paralysis
Glaucoma (decrease aqueous humor formation)
Altitude (mountain) sickness (decrease CSF and pH)
Metabolic Alkalosis
Epilepsy (seldom used)

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21
Q

What are the adverse effects of carbonic anhydrase inhibitors?

A 
A PACE
acidosis (metabolic)
potassium depletion
allergic reactions (sulfonamide based)
Ca+ nephrolithiasis
encephalopathy
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22
Q

In what patient population are carbonic anyhdrase inhibitors contraindicated?

A

can cause hepatic encephalopathy in patients with cirrhosis of liver

**By producing an alkaline urine, CA inhibitors decrease excretion of NH4+ in the urine
This can lead to hyper-ammonemia and hepatic encephalopathy in patients with cirrhosis of the liver

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23
Q

These are the osmotic diuretics

A

mannitol
glycerin
isosorbide
urea

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24
Q

How do osmotic diuretics work?

A

freely filtered in the glomerulus
undergo limited reabsorption
quantity of water retained in proportional to the quantity administered

**act primarily in the proximal tubule and to a lesser extend in the ascending loop of Henle

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25
Q

When are osmotic diuretics used?

A

AAA ID

Acute tubular necrosis (increase urine volume in case of acute GFR decrease)
Anuria in hemolysis or rhabdomyolysis (prophylaxis use)
Angle-closed glaucoma (reduce intraocular pressure)
Increased intracranial pressure (used as the DOC)
Dialysis disequilibrium

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26
Q

When should osmotic diuretics not be used?

A

CHF

severe renal disease

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27
Q

What are the adverse effects of osmotic diuretics?

A

if administered too rapidly, can decrease cell volume and impair cell function
dehydration
hyperkalemia
hyponatremia

28
Q

Name 3 adenosine A1 receptor antagonists

A

caffeine
Rolophylline
theophylline

29
Q

How do adenosine A1 receptor antagonists work?

A

interfere with the Na+/H+ exchanger in the proximal convoluted tubule
adenosine-mediated enhancement of K+ secretion in the collecting tubule

30
Q

Which 2 loop diuretics are sulfonamide derivatives?

Non-sulfonamide derivate?

A

Furosemide & torsemide

Ethacrynic acid

31
Q

How do loop diuretics work? Where do they work in the kidney? What do they block?

A

Inhibit Na/K/Cl cotransporter in the ascending limb of Henle which decreases hyperosmolarity in the medullary interstitium

32
Q

Clinical use of loop diuretics

A

Edema related:
emergency situations of acute pulmonary edema
edema of cardiac, hepatic or renal origin

Electrolyte or drug-related:
Acute hypercalcemia
Hyperkalemia - give with Na+ and water
Useful for anion overdose (Br-, Fl-, I-) in addition to saline
Torsemide: can decrease blood pressure without diuresis - useful for mild to moderate hypertension

33
Q

Adverse effects of loop diuretics?

A

Ototoxicity & transient deafness
Diabetogenic (furosemide & bumetanide)
Compete for binding to serum proteins with drugs, such as warfarin and clofibrate
Reduced clearance of Li+
Hyperuricemia due to increased reabsorption of uric acid in proximal tubule caused by decreased vascular volume
Hypomagnesemia
Severe vascular volume decrease
Can lead to hyponatremia if patients increase H2O intake due to hypovolemia-induced thirst
Can decrease LDL and triglyceride levels

34
Q

Contraindications to loop diuretic use?

A

severe Na+ and volume depletion

hypersensitivity to sulfonamides

35
Q

Sulfonamide derivative found while trying to make a better CA inhibitor; produces a diuresis with increase Cl- (not HCO3-); effective in both acidic and alkaline conditions

A

thiazide diuretics

**hydrochlorothiazide

36
Q

How do thiazide diuretics work?

A

inhibit Na+ and Cl- co-transport in the DISTAL tubule; increase Na+ and Cl- in the urine

**weak diuretic since only 5% of filtered Na+ in reabsorbed in the distal tubule

37
Q

What do thiazide diuretics do to the reabsorption of Ca++?

A

increase overall reabsorption

38
Q

Why are thiazide diuretics preferred?

A

cause less distortion of the ECF bc they cause a modest diuresis & effect the excretion of several ionic species

39
Q

What are thiazide diuretics used for?

A 
edema associated with CHF
hypertension
Ca++ nephrolithiasis
bromide intoxication
diabetes insipidus
40
Q

Adverse effects of thiazide diuretics?

A

**Increased cholesterol (5-15% - transient) & LDL
Hypokalemia with prolonged therapy
Associated with arrhythmias in some settings
Hyperglycemia
Hypokalemic metabolic alkalosis
Hyperuricemia

Hyponatremia

41
Q

the volume of fluid filtered from the glomerular capillaries into the Bowman’s capsule per unit time

A

Glomerular filtration rate (GFR)

[Urine conc * Urine flow]/plasma concentration

42
Q

Which diuretics do not act on the luminal surface?

A

aldosterone antagonists

43
Q

How are diuretics that are not filtered at the glomerulus transported into the nephron?

A

organic acid or base transporters in the proximal tubule

44
Q

What decreases diuretic access to the tubule lumen?

A

decreased renal blood flow (decreased GFR)

45
Q

Why are diuretics that act proximally weak?

Why are diuretics that act distally weak?

A

even though 70-80% of the filtered load is handles there, their actions are counteracted by more distal reabsorption

diuretics that act distally are weak bc only 5-10% of the filtered load is involved

46
Q

Why are loop diuretics the most effective?

A
  1. they inhibit an important transport mechanism (Na/K/Cl transporter)
  2. the affected site handles a large fraction of the filtered load (15-50%)
  3. more distal mechanisms cannot compensate
47
Q

How do loop and thiazide diuretics differ in how they affect concentration/dilution of urine?

A

loop diuretics act on the ascending limb of the loop of Henle, where Na+ is reabsorbed but water is trapped - so loop diuretics impair both the concentration and dilution of urine

thiazide diuretics act distal to the loop of Henle, so they can influence dilution, but not concentration

48
Q

This loop diuretic can decrease blood pressure without diuresis

A

Torsemide

49
Q

Thiazide-like diuretic, that has anti-hypertensive actions independent of its diuretic activity; used in cases of renal failure together with loop diuretics

A

Indapamide

50
Q

This thiazide-like diuretic is efficacious and can be given in combo with a loop diuretic; can be effective in renal insufficiency

A

Metolazone

51
Q

Why does hypokalemia occur with diuretics?

A

K+ is exchanged for Na+ in the distal nephron

52
Q

This is an aldosterone agonist that is a K+ sparing diuretic

A

Spironolactone

53
Q

What does aldosterone do?

A

essentially it increases Na+ reabsorption and K+ excretion

54
Q

These are two non-aldosterone agonists that are K+ sparing diuretics

A

Triamterene

Amiloride

55
Q

How do non-aldosterone antagonist, K+ sparing diuretics work?

A

decrease Na+ reabsorption in the distal nephron - with less Na+ uptake there is a decrease in K+ loss

56
Q

What should you use to treat hepatic cirrhosis and ascites?

A

thiazide, loop, and K+ sparing diuretics

57
Q

What should you use to treat pulmonary edema?

A

loop diuretics

58
Q

What should you use to treat cerebral edema?

A

osmotic diuretics for direct effects

59
Q

What do you use to treat nephrotic syndrome? Acute renal failure? Chronic renal failure?

A

thiazide diuretics, decrease Na+ intake
osmotic or loop diuretics
treat aggressively with loop diuretics

60
Q

How to treat hypertension?

A

decrease salt intake

add thiazides, maybe a K+ sparing or loop diuretic

61
Q

How to treat nephrolithiasis?

A

treat with thiazides to increase Ca++ reabsorption

decrease salt intake

62
Q

How to treat hypercalcemia?

A

treat with loop diuretics to increase calcium excretion

+ normal saline to prevent contraction of extracellular space, +/- K+ sparing diuretics as needed

63
Q

How to treat nephrogenic diabetes insipidus?

A

treat with thiazide or loop diuretics to reduce plasma volume and contract the extracellular space

64
Q

What is diabetes insipidus?

A

increased urine output due to decreased ADH

65
Q

What are the two types of diabetes insipidus? Which type will respond to desmopressin, an ADH analog?

A

central: decreased ADH due to injury, tumor or infection **will improve with desmopressin
nephrogenic: decreased ADH responsiveness **won’t respond to treatment with desmopressin

66
Q

What is SIADH?

A

syndrome of inappropriate secretion of ADH –> too much ADH –> too much H20 reabsorption

Block 9 Week 2 Meg (8 decks)

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