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Life support > Renal Diuretics > Flashcards

Renal Diuretics Flashcards

1
Q

What do Diuretics cause?

A

Diuretics cause an increase in urine output (diuresis)

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2
Q

What do diuretics produce an increased excretion of?

A

Many diuretics also produce increased excretion of
Na (natriuresis) and K (producing hypokalaemia)

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3
Q

What are diuretics used in?

A

used in hypertension,
acute pulmonary oedema, heart failure

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4
Q

What are the 2 major groups of diuretics?

A
  1. Mainly affect H20 excretion
  2. Increase in electrolyte excretion
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5
Q

What is included in diuretics that mainly affect H20 excretion?

A
  1. Water
  2. Ethanol(Reduce ADH release)
  3. Osmotic diuretics
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6
Q

What is included in diuretics that cause an increase in electrolyte excretion?

A
  1. Carbonic anhydrase inhibitors
  2. Loop diuretics
  3. Thiazides
  4. K-sparing diuretics
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7
Q

What is the mechanism of action of diuretics on site 1?

A

Reabsorption of Na with passive movement of
organic molecules (glucose, amino acids) and H2O

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8
Q

What is the mechanism of action of diuretics on site 2?

A

Reabsorption of Na for H (Na/H exchanger) - Role of carbonic anhydrase

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9
Q

Where are both site 1 and site 2 located in the nephron?

A

Proximal convoluted tubule

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10
Q

Where is site 3 located in the nephron?

A

Loop of Henle

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11
Q

What is the mechanism of action of diuretics on site 3?

A

Transport of NaCl by a co-transporter for Na, K, 2Cl
-Interstitial fluid becomes hypertonic, aiding reabsorption of H20 from the collecting duct(controlled by ADH)

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12
Q

What is the permeability of thick ascending liip of henle to H20 like?

A

Thick ascending Loop of Henle is NOT permeable to H2O

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13
Q

Where are site 4, site 5 and site 6 located in the nephron?

A

Distal convoluted tubule

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14
Q

What is the mechanism of action on site 4 of diuretics?

A

Reabsorption of Na/Cl (co-transporter) followed by H2O

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15
Q

What is the mechanism of action on site 5 of diuretics?

A

Na is reabsorbed (through ENaC channels) in exchange for K efflux
(through K channels) - stimulated by aldosterone

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16
Q

What is the mechanism of action on site 6 of diuretics?

A

Na is reabsorbed and H+ lost via Na-H exchanger
- stimulated by aldosterone

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17
Q

What can an overactive site 5 produce?

A

Overactive Site 5 can produce K+ loss and plasma hypokalaemia

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18
Q

What can an overactive site 6 produce?

A

Overactive Site 6 can produce plasma alkalosis due to increased H+ excretion

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19
Q

What is an example of agent that mainly affect H20 excretion and how is it administred?

A

Mannitol
-Usually administered i.v.

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20
Q

How does mannitol work?

A

-High concentrations in plasma
-Causes increased osmolarity in tubules
-Results in decreased reabsorption of H20

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21
Q

Where does mannitol act at?

A

Acts at PCT, DCT, and collecting duct

22
Q

What are the uses of mannitol?

A

-Reduce intracranial and intraocular pressure
-Prevent acute renal failure
-Excrete some types of poisoning

23
Q

How does mannitol work to reduce intracranial and intraocular pressure?

A

-Mannitol does not enter the CNS
-Creates an osmotic gradient from cells to plasma
-H2O leaves the CNS (CSF into plasma)
-H2O leaves plasma into tubules and then urine

24
Q

How do diuretics that affect electrolyte excretion work?

A

Drugs increase urine flow by increasing excretion of Na (natriuresis)
– where Na goes H2O follows (osmosis)

25
Q

What is the major determinant of ECFV?

A

NaCl is the major determinant of extracellular fluid volume (ECFV)

26
Q

What will NaCl excretion from ECF lead to?

A

Increased NaCl excretion leads to decreased ECFV leads to decreased Blood vol which leads to decreased Cardiac output which ultimately decreases Oedema

27
Q

What is an example of a diuretic that affects electrolyte excretion and what type is it?

A

Carbonic anhydrase inhibitors
-Acetazolamide

28
Q

How does acetazolamide work including what site it acts on?

A

Inhibit the activity of CA - decrease formation of H+ / HCO3- in the luminal cells of PCT (Site 2)
Less Na+ uptake - less H2O uptake

29
Q

What are non renal effects that acetazolamide can be used in?

A

In glaucoma, aqueous humor formation
is dependent on carbonic anhydrase activity

30
Q

What is an example of a loop diuretic?

A

Furosemide

31
Q

What is the mechanism by which furosemide works?

A

Inhibit Na/K/Cl co-transporter at thick ascending loop of Henle (Site 3)
decreasing Reabsorption of Na, K, and 2Cl – marked loss of these electrolytes

32
Q

What does furesomide prevent concentration of and therefore how does this impact water loss?

A

Prevents concentration of cortico-medullary interstitial fluid and therefore
reduces effect of ADH on the collecting duct (less osmotic drive) - Increasing H2O loss

33
Q

What are the uses of furosemide?

A
  1. Chronic heart failure
  2. Acute renal failure
  3. Acute pulmonary oedema
34
Q

What does furosemide do in chronic heart failure?

A
  1. Decreases ECFV therefore decreases congestion
35
Q

How does furosemide produce vasodilation?

A

Produces vasodilation due to increased PCI2 released in blood vessels

36
Q

How does furosemide work in acute renal failure?

A

Increase renal blood flow

37
Q

How does furosemide work in acute pulmonary oedema?

A

Decrease capillary pressure

38
Q

What are compensation mechanisms/side effects at site 5 and site 6 due to furosemide?

A

-Site 5 - Increase Na uptake via ENaC – increase K excretion – K loss (hypokalaemia)
-Site 6: Increase Na uptake via Na/H exchanger– H loss (metabolic alkalosis)

39
Q

What is an example of a thiazide diuretic?

A

Bendrofluazide

40
Q

What is the mechanism of action of bendrofluazide?

A

Inhibit Na/Cl uptake via co-transporter at distal convoluted tubule (Site 4)

41
Q

What is the compensation mechanism/ side effects of bendrofluazide at site 5 and site 6?

A

Site 5: Increase Na uptake via ENaC – increase K excretion – K loss (Hypokalaemia)
Site 6: Increase Na uptake via Na/H exchanger – H loss (Metabolic alkalosis)

42
Q

What are the uses of bendrofluazide?

A

-Treatment of hypertension
-Treatment of mild heart failure

43
Q

How does the treatment of hypertension by bendrofluazide work?

A
  1. Diuresis causes a decrease in blood volume therefore a decrease in cardiac output
  2. Major effect is causing vasodilation which results in a decreased TPR
44
Q

How does the treatment of mild heart failure work by bendrofluazide?

A

Decreased ECFV leads to decreased Oedema

45
Q

What is the mechanism of K-sparing diuretics?

A

Important as they reduce Na reabsorption without losing K
- counter the powerful electrolyte secretions of diuretics such as frusemide -

46
Q

Where do K-sparing diuretics act?

A

Act at end of DCT and collecting duct (Sites 5 + 6)

47
Q

What are examples of K-sparing diuretics?

A
  1. Spironolactone
  2. Amiloride
48
Q

What type of antagonist is spironolactone and what sites does it act on?

A

Competitive antagonist of aldosterone
at sites 5 and 6

49
Q

What conditions is spironolactone used for?

A

CVS diseases linked to overproduction of
aldosterone  volume overload
e.g., Heart failure

50
Q

What does amiloride do and what site does it act on?

A

Reduces Na reabsorption and K loss
Blocks ENaC at site 5

51
Q

How do ACE inhibitors work?

A

Decrease Ang II formation which decreases aldosterone

Life support (38 decks)

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