Session 7 - Diuretics Flashcards

1
Q

Define diuresis

A

• Increased formation of urine by the kidney

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2
Q

Define diuretics

A

• Block reabsorption of Na+ and therefore water by the kidney

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3
Q

Give three main types of diuretics

A
  • Loop diuretics
    • Thiazide diuretics
    • K+ sparing diuretics and aldosterone antagonists
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4
Q

How do loop diuretics work?

A
  • Acts on TAL of the loop of henle
    • Block Na-K-2Cl
    • Causes excretion of 10-25% of filtered Na+ ions (segments downstream also have limited capacity to reabsorb water, increasing diuresis)
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5
Q

Name two loop diuretics

A
  • Furosemide

* Bumetanide

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6
Q

What do Thiazide diuretics do?

A
  • Act on early DCT
    • Block Na-Cl co-transporter
    • Inhibits only 5% of Na+ reabsorption
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7
Q

Give a thiazide diuretic

A

• Bendroflumethiazide

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8
Q

Where do K+ sparing diuretics and aldosterone antagonists work?

A
  • Late DCT and collecting duct
    • Reduce ENaC reabsorption of sodium
    • Inhibit 2% Na+ reabsorption
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9
Q

Why are K+ sparing diuretics named thus?

A

Reduce the loss of K+ and can produce life threatening hyperkalaemia

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10
Q

Give an example of a K+ sparing diuretic

A

• Amiloride

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11
Q

Give an example of an aldosterone antagonist

A

• Spironolactone

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12
Q

Give overall dangers of diuretics

A
  • Hyper/hypokalaemia

* RAAS activation

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13
Q

Outline the negatives of using K+ sparing diuretics/Aldosterone Antagonists

A

• Reduce loss of K+ and may produce life threatening hyperkalaemia

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14
Q

Give a negative effect of loop diuretics

A

• Reduces calcium absorption, inducing urinary excretion

Patient may become hypocalcaemi

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15
Q

What do loop and thiazide diuretics do?

A

• Increase the loss of potassium in the urine

Hypokalaemia

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16
Q

Outline how loop and thiazide diuretics cause hypokalaemia

A
  • Block Na+ and H20 reabsorption in LoH or early DCT
    • Increase Na+ and H20 delivery to late DT + CD
    • Increase Na+ absorption by principle cells/Faster flow rate of filtrate so K+ washed away faster
    • Favourable electrical gradient for K+ excretion/Low K+ concentration in lumen
17
Q

How do K+ sparing diuretics cause hyperkalaemia?

A
  • Block epithelial Na+ channels
    • Reduce Na+ reabsorption
    • Reduce potassium loss in urine
    • Hyperkalaemia
18
Q

How do aldosterone antagonists cause hyperkalaemia?

A
  • Block of action of aldosterone
    • Reduce activity of Na/K+ ATPase & epithelial Na+ channels
    • Reduce Na+ reabsorption
    • Reduce potassium loss in urine
    • Hyperkalaemia
19
Q

What do all diuretics do?

A
  • Reduce ECF volume so activate RAAS

* This increases aldosterone secretion, increase Na+ reabsorption and K+ secretion, contributing to hypokalaemia

20
Q

List negative effects which come about as a result of diuretics use and abuse

A
  • Hypokalaemia
    • Hyperkalaemia
    • RAAS activation
    • Hypovolaemia
    • Hyponatraemia
    • Increased uric acid levels in blood
    • Metabolic effects
21
Q

What is hypovolaemia?

A

• Decreased ECF volume due to excessive loss of Na+ and water

22
Q

What 3 things must be done to avoid hypovolaemia?

A
  • Monitor weight
    • Look for signs of dehydration
    • Check BP
23
Q

What is hyponatraemia?

A

• Decreased sodium in blood

Multiple symptoms, including nausea, vomiting, headache and confusion

24
Q

What do increased uric acid levels in blood cause?

A

Gout

25
Q

What are two negative metabolic effect of diuretic use?

A
  • Glucose intolerance

* Increased LDL levels

26
Q

What is a carbonic anhydrase inhibitor?

A

• Diuretic which acts in PCT by inhibitng enzyme carbonic anhydrase to interfere with Na+ and HCO3- reabsorption

27
Q

Why is carbonic anhydrase no longer used a diuretic?

A

• HCO3- loss leads to metabolic acidosis

28
Q

Give six conditions diuretics used to treat

A
  • Conditions with ECF expansion and Oedema
    • Acute pulmonary oedema
    • Hypertension
    • Hypercalcaemia
    • Cerebral oedema (Osmotic diuretics)
    • Glaucoma (carbonic anydrase)
29
Q

Give four conditions which involve ECF expansion and oedema

A
  • Congestive heart failure
    • Nephrotic syndrome
    • Kidney failure
    • Ascites and oedema due to liver cirrhosis
30
Q

What is acute pulmonary oedema usually due to?

A

• Left heart failure

31
Q

What is pulmonary oedema treated with?

A

• Loop diuretics

32
Q

What is hypertension treated with?

A
  • Thiazide diuretics

* Spironolactone in primary hyperaldosteronism (Conn’s syndrome)

33
Q

How is hypercalcaemia treated?

A

• Loop diuretics promote Ca2+ excretion in loop of henle

34
Q

Give three substances with diuretic actions

A
  • Alcohol - Inhibits ADH release
    • Coffee - Increased GFR, decreased Na+ reabsorption
    • Lithium - Inhibits ADH action on collection ducts
35
Q

What is diuresis expressed as in the form of a symptom?

A

• Polyuria

36
Q

Give four causes of polyuria that are non drink related

A

• Diabetes mellitus
○ Glucose in filtrate -> Osmotic diuresis
• Central diabetes insipidus
○ Decreased ADH release from posterior pituitary -> Diuresis
• Nephrogenic diabetes insipidus
○ Poor response of collecting ducts to ADH -> Diuresis
• Psychogenic polydypsia
○ Increased intake of fluid