Renal Control of Fluid and Electrolytes and Introduction to Diuretics

Question 1

• What is the distinction between dehydration and hypovolaemia

Answer 1

Dehydration – loss of water, osmolality increases

Hypovolaemia – loss of blood volume, osmolality remains same

Question 2

• What could cause a primary loss of Na?

Answer 2

Diarrhoea, vomiting, diuretics, Addison’s

Question 3

• What is hypernatremia?

Answer 3

Excessive amounts of Na in the blood

Question 4

• What is pressure natriuresis?

Answer 4

Acute increase in pressure causes a 2-3 fold increase in excretion of Na

Question 5

• Why is there amplified coupling between pressure and Na excretion?

Answer 5

Because pressure inhibits mechanisms for sodium conservation

Question 6

• What happens in the event of haemorrhage?

Answer 6

Baroreflex, increases renal SNS activity – RAAS activated, renal arteriole constriction

Question 7

• What is the relationship between GFR and Na+?

Answer 7

Inverse relationship between GFR and [Na+] at the macula densa

Question 8

• What are diuretics?

Answer 8

Drugs that increase the rate of urine flow and excretion of Na+ and water from the filtrate

Question 9

• When would you use diuretics?

Answer 9

Oedema, forced diuresis (intoxications), correct specific ion imbalances

Question 10

• Which drugs act directly on cells of the nephron?

Answer 10

Carbonic anhydrase inhibitors, loop diuretics, thiazides, potassium-sparing diuretics

Question 11

• What are two examples of potassium-sparing diuretics?

Answer 11

Triamterene and amiloride & aldosterone antagonists

Question 12

• Which drugs act indirectly on cells of the nephron?

Answer 12

Osmotic diuretics

Question 13

• How is tolerance induced?

Answer 13

By an increase in plasma angiotensin, renin and aldosterone or compensatory activity in other parts of the nephron