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Urinary > 10 - Regulation of Potassium > Flashcards

10 - Regulation of Potassium Flashcards

1
Q

What is Bartter’s syndrome?

A
  • Inherited
  • Thick ascending limb the NKCC2 is inhibited so low serum K+, increased blood pH, normal-low B.P, hypercalcuria so chance of stones
  • Sensorineural hearing loss as this transporter also in ear
  • Fluid replacement with electrolytes
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2
Q

What are normal potassium levels in the body?

A

Intracellular 140 mmol/L

Serum 3.5-5.5 mmol/L

Needed in ICF to maintain cell volume, regulate pH, control cell enzyme function, DNA and protein synthesis and cell growth

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3
Q

What can happen is potassium levels are too high or too low?

A
  • Cardiac arrhytmias and arrest
  • Nerve dysfunction so muscle weakness and cramps
  • Constipation

- Low ECF: inability of kidneys to form concentrated urine, metabolic alkalosis, enhancement of renal ammonium excretion

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4
Q

What are some sources of potassium in our diets?

A
  • Banana
  • Coconut
  • Tomatoes
  • Potato
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5
Q

Where in the nephron is potassium reabsorbed and secreted?

A
  • Majority in PCT paracellularly and K/Cl transporter
  • 20-25% in thick ascending limb via NKCC2
  • In DCT transport with calcium and magnesium
  • In CD secretion with H+ under influence of aldosterone
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6
Q

What are some causes of hyperkalaemia?

A
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7
Q

How can we treat hyperkalaemia?

A

Need to enhance Na/K ATPase pump

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8
Q

What is hypokalaemia caused by?

A
  • Vomiting
  • Magnesium deficiency
  • Primary and Secondary hyperaldosteronism
  • Increased urine flow
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9
Q

How can we treat hypokalaemia?

A
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10
Q

Why do we often have to administer a mixture of two diuretics?

A

Diuretics tend to only work on one portion of the nephron and the nephron can compensate for the altered sodium reabsorption at different segments so blocking two segments increases drug efficacy

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11
Q

What is the only diuretic that works on the PCT and what is it now used for instead of a diuretic and why?

A

- Carbonic anhydrase inhibitors, e.g acetazolamide, stop NaHCO3 reabsorption rather than NaCl

  • Not that effective as less sodium bicarbonate than NaCl and this was leading to metabolic acidosis
  • Used for glaucoma to reduce formation of aqueous humour and infantile epilepsy
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12
Q

What are some different classes of diuretics, where do they work in the nephron and what are some examples of each class?

A
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13
Q

What happens to serum potassium during intense exercise?

A

Increases

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14
Q

Where does excretion of potassium from the body occur?

A
  • 80% kidney
  • 20% faeces and sweat

GFR = 125ML/MIN

Serum K+ = 4

Total removal a day = 800mmol/L

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15
Q

What factors increase Na/K ATPase activity?

A
  • K+ concentration in plasma
  • Insulin
  • Noradrenaline effect on B2 adrenoreceptors
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16
Q

What factors can affect K+ secretion in the collecting duct?

17
Q

What is Liddle’s syndrome?

A
  • Autosomal dominant disease that causes increased activity of ENaC in the collecting duct
  • Increased excretion of K but overabsorption of Na and H2O
  • High B.P, low blood K+, metabolic alkalosis, lowered renin and aldosterone
18
Q

What is the normal GFR for men and women?

A

125ml/min for men

90ml/min for women

19
Q

What is the urinary and vascular pole in the nephron?

A
  • Vascular pole is where arterioles enter and leave the Bowman’s capsule
  • Urinary pole is where PCT starts
20
Q

A patient has a BP of 100/60, what is the response of the macula densa cells?

A

Stimulate the JGA to release renin

21
Q

What effect does sweating have on urine voulume and blood osmolality if someone didn’t take a drink for 12 hours and was exercising?

A

Volume decreases but osmolality stays the same

22
Q

After general anaesthetic a patient may not void urine for a period of time as the kidneys have stopped making urine, what is this called?

23
Q

A 65 year old man has had a syncopal episode after not drinking for 12 hours, what will happen to his urine osmolarity and renal clearance of sodium?

A
  • Osmolarity will increase
  • Renal clearance will decrease
24
Q

A woman presents with hyperparathyroidism, what effect will this have on her phosphate levels in the blood and why?

A

Increased excretion of phosphate in the urine as PTH inhibits Na/Pi channel in the PCT so more phopshate in the urine

25
Q

A young girl presents with an eating disorder where she has been making herself vomit, she has hypokalaemia, why is this?

A

Increased kidney tubular potassium secretion due to the loss of H+ in the vomit so metabolic alkalosis. Losing potassium to correct acid base status

Urinary (21 decks)

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