Flashcards in Session 7 - Diuretics Deck (36):
1
Define diuresis
• Increased formation of urine by the kidney
2
Define diuretics
• Block reabsorption of Na+ and therefore water by the kidney
3
Give three main types of diuretics
• Loop diuretics
• Thiazide diuretics
• K+ sparing diuretics and aldosterone antagonists
4
How do loop diuretics work?
• 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)
5
Name two loop diuretics
• Furosemide
• Bumetanide
6
What do Thiazide diuretics do?
• Act on early DCT
• Block Na-Cl co-transporter
• Inhibits only 5% of Na+ reabsorption
7
Give a thiazide diuretic
• Bendroflumethiazide
8
Where do K+ sparing diuretics and aldosterone antagonists work?
• Late DCT and collecting duct
• Reduce ENaC reabsorption of sodium
• Inhibit 2% Na+ reabsorption
9
Why are K+ sparing diuretics named thus?
Reduce the loss of K+ and can produce life threatening hyperkalaemia
10
Give an example of a K+ sparing diuretic
• Amiloride
11
Give an example of an aldosterone antagonist
• Spironolactone
12
Give overall dangers of diuretics
• Hyper/hypokalaemia
• RAAS activation
13
Outline the negatives of using K+ sparing diuretics/Aldosterone Antagonists
• Reduce loss of K+ and may produce life threatening hyperkalaemia
14
Give a negative effect of loop diuretics
• Reduces calcium absorption, inducing urinary excretion
Patient may become hypocalcaemi
15
What do loop and thiazide diuretics do?
• Increase the loss of potassium in the urine
Hypokalaemia
16
Outline how loop and thiazide diuretics cause hypokalaemia
• 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
How do K+ sparing diuretics cause hyperkalaemia?
• Block epithelial Na+ channels
• Reduce Na+ reabsorption
• Reduce potassium loss in urine
• Hyperkalaemia
18
How do aldosterone antagonists cause hyperkalaemia?
• Block of action of aldosterone
• Reduce activity of Na/K+ ATPase & epithelial Na+ channels
• Reduce Na+ reabsorption
• Reduce potassium loss in urine
• Hyperkalaemia
19
What do all diuretics do?
• Reduce ECF volume so activate RAAS
• This increases aldosterone secretion, increase Na+ reabsorption and K+ secretion, contributing to hypokalaemia
20
List negative effects which come about as a result of diuretics use and abuse
• Hypokalaemia
• Hyperkalaemia
• RAAS activation
• Hypovolaemia
• Hyponatraemia
• Increased uric acid levels in blood
• Metabolic effects
21
What is hypovolaemia?
• Decreased ECF volume due to excessive loss of Na+ and water
22
What 3 things must be done to avoid hypovolaemia?
• Monitor weight
• Look for signs of dehydration
• Check BP
23
What is hyponatraemia?
• Decreased sodium in blood
Multiple symptoms, including nausea, vomiting, headache and confusion
24
What do increased uric acid levels in blood cause?
Gout
25
What are two negative metabolic effect of diuretic use?
• Glucose intolerance
• Increased LDL levels
26
What is a carbonic anhydrase inhibitor?
• Diuretic which acts in PCT by inhibitng enzyme carbonic anhydrase to interfere with Na+ and HCO3- reabsorption
27
Why is carbonic anhydrase no longer used a diuretic?
• HCO3- loss leads to metabolic acidosis
28
Give six conditions diuretics used to treat
• Conditions with ECF expansion and Oedema
• Acute pulmonary oedema
• Hypertension
• Hypercalcaemia
• Cerebral oedema (Osmotic diuretics)
• Glaucoma (carbonic anydrase)
29
Give four conditions which involve ECF expansion and oedema
• Congestive heart failure
• Nephrotic syndrome
• Kidney failure
• Ascites and oedema due to liver cirrhosis
30
What is acute pulmonary oedema usually due to?
• Left heart failure
31
What is pulmonary oedema treated with?
• Loop diuretics
32
What is hypertension treated with?
• Thiazide diuretics
• Spironolactone in primary hyperaldosteronism (Conn's syndrome)
33
How is hypercalcaemia treated?
• Loop diuretics promote Ca2+ excretion in loop of henle
34
Give three substances with diuretic actions
• Alcohol - Inhibits ADH release
• Coffee - Increased GFR, decreased Na+ reabsorption
• Lithium - Inhibits ADH action on collection ducts
35
What is diuresis expressed as in the form of a symptom?
• Polyuria
36