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chronic kidney disease/renal replacement > Diuretics > Flashcards

Diuretics Flashcards

1
Q

What are diuretics uses for

A

Chronic heart failure

Hypertension

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2
Q

How do diuretics work

A

They increase Na+ excretion (natriuresis) which is followed osmotically by water

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3
Q

Where do osmotic agents act

A

PCT and descending limb

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4
Q

Where do loop diuretics act

A

Ascending limb

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5
Q

Where do Thiazides act

A

DCT

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6
Q

Where do K-sparing agents act

A

Collecting duct

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7
Q

How do osmotic diuretics act

A

Increase osmolality of tubular fluid in the PCT and loop of Henle and reduces passive reabsorption of H20

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8
Q

What are osmotic diuretics used for

A

Cerebral oedema

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9
Q

How strong are loop diuretics and how do they act

A

Very powerful

Block Na+/2Cl-/K+ symporter of the thick ascending limb of the loop of Henle so ions don’t leave the loop of henle which means that less water is reabsorbed into the interstitium

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10
Q

How do loop diuretics affect Na+ and what’s a consequence of this

A

Increase Na+ delivery to DCT

-Promotes K+ loss which may lead to hypokalaemia

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11
Q

What do loop diuretics do to macula densa cells

A

Decrease Na+ entry into macula densa

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12
Q

What other conditions are loop diuretics used in and why

A

Hypercalcaemia

-Reduces absorption of cations and causes loss of Ca2+ and Mg2+

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13
Q

What is the effect of loop diuretics on kidneys after use

A

Kidney becomes refractory

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14
Q

Uses of loop diuretics

A
  • Chronic heart failure- reduce pulmonary oedema secondary to LVF and peripheral oedema
  • Venodilators. Rapid effect in acute LVF
  • REnal failure to improve diuresis
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15
Q

What is the mode of action of thiazides

A

Inhibit active Na+ reabsorption and accompanying Cl-

–>this means there’s increased solute in tubular fluid and so decreases H20 reabsorption gradient

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16
Q

When are thiazides used

A

Second line drug in hypertension

Mild to moderate heart failure

17
Q

When are thiazides not useful

A

IN moderate renal impairment because they’re really excreted by the weak acid transporter in the PCT prior to acting on DCT

18
Q

Which diuretic is useful in renal failure

A

Loop diuretics

19
Q

What is hypokalaemia secondary to

A

Loop diuretics

Thiazides

20
Q

How do diuretics cause hypokalaemia

A

Decrease Na+ in extracellular fluid

loops block Nacl entry to macula densa

Cause volume depletion: which activates the RAAS (Na+ retention and K+ loss)

21
Q

Whats the problem with hypokalaemia

A

More negative membrane potential

Cardiac arrhythmias

Reduces activity of Na+ K+ pump- potentiates the action of digoxin

22
Q

How does alkalosis occur in relation to the DCT

A

Na+ delivery to the DCT is associated with H+ loss which leads to alkalosis

23
Q

What is the mode of action of potassium sparing diuretics

A

Aldosterone receptor antagonists

Na+ channel blockers (weak diuretics but in combination with K+ losing agents may reduce K+ loss)

24
Q

How to stop hypokalaemia in potassium sparing diuretics

A

Combine with K+ losing agents

or

Combine with ACEI because they cause hyperkalaemia so may negate the effects of K-losing diuretics

25
Q

What is the mode of action of aldosterone receptor antagonists

A

Antagonise aldosterone receptors

-Prevent insertion of Na+ pumps and channels

26
Q

When are aldosterone receptor antagonists used

A

primary and secondary hyperaldosteronism (ascites associated with liver failure)

Low dose spironolactone used in CHF to block the actions of aldosterone on the heart

27
Q

What is the mode of action of sodium channel blockers

A

Block luminal Na+ channels in late DCT and CD

-Na+ no longer retained at expense of K+

28
Q

What is a leading cause of chronic renal failure

A

Diabetes

29
Q

What drugs appear to slow renal damage

A

ACE inhibitors

30
Q

How should diuretics be counselled in practice

A
  • Best taken in morning
  • Patients will experience an increase in urine flow
  • Patients should avoid excess salt in diet
  • May cause postural hypotension (especially in elderly)
  • NSAIDs may reduce the effects of loop diuretics
  • electrolytes should be monitored
31
Q

How should thiazides be counselled

A

May uncover/worsen diabetes

May worsen gout (type of arthritis where crystals form around the joints)

chronic kidney disease/renal replacement (6 decks)

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