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Nephrology > Potassium metabolism - Showkat > Flashcards

Potassium metabolism - Showkat Flashcards

1
Q

Where is the majority of potassium in the body?

A

ICF - muscle

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2
Q

What routes excrete potassium?

A

Renal (90%)

GI (10%)

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3
Q

Where is potassium excreted in the nephron?

A

CD (principal cells) - ROMK (renal outer medullary) channel

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4
Q

Where is potassium reabsorbed in the nephron?

A

TALH- NaK2Cl and paracellularly

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5
Q

What factors affect potassium secretion in the distal tubule?

A 
Concentration gradient (based on serum [K])
Electrical gradient (based on [Na] in lumen)
K permeability (based on aldosterone)
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6
Q

What are causes of decreased renal potassium secretion?

A

Renal failure
Distal tubular dysfunction
Decreased distal tubular flow
Hypoaldosteronism

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7
Q

What are causes of increased renal potassium secretion?

A 
Bartter's syndrome / Gitelman's Syndrome (Increased Na delivery)
Diuretics
Hyperaldosteronism (prolonged vomiting or nasogastric suction)
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8
Q

What factors affect internal potassium balance?

A 
Plasma potassium concentration
Insulin
Epinephrine
Acid-Base disturbance
Plasma Tonicity
Cell Lysis and Proliferation
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9
Q

How do changes in extracellular pH produce affect K?

A

Reciprocal shifts in H and K

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10
Q

What are the relative extracellular potassium concentrations in extracellular acidosis and alkalosis?

A

Acidosis - Hyperkalemia

Alkalosis - Hypokalemia

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11
Q

Loss of intracellular water or plasma hypertonicity would have what effect on K?

A

Potassium would leave the cell via solvent drag

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12
Q

What would the effects of cell lysis or proliferation have on extracellular potassium?

A

Lysis (Rhabdomyolysis, hemolysis) - Increased extracellular potassium
Proliferation - Decreased extracellular potassium

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13
Q

What are three major causes of potassium concentration?

A

Intake
Excretion
Internal Distribution

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14
Q

What are causes of internal redistribution that would produce hyperkalemia?

A 
Insuline deficiency
Beta2-Adrenergic blockade
Hypertonicity
Acidemia
Cell lysis
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15
Q

What are signs of hyperkalemia?

A 
Peaked T-wave
Wide QRS complex
Absent P-wave
Sine-wave morphology
Bradyarrythmias
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16
Q

What is the treatment for hyperkalemia?

A 
Stabilize cardiac muscle - IV Ca
Insulin
Beta agonist
Bicarbonate
Diuretics
Resins (GI tract)
Dialysis
17
Q

What is the quickest and slowest acting treatment of hyperkalemia?

A

Quickest - Calcium

Slowest - Resin

18
Q

What are causes of internal redistribution that would produce hypokalemia?

A

Insulin excess
Catecholamine excess (epinephrine)
Alkalemia
Cell proliferation

19
Q

What causes normotensive hypokalemia?

A

Renal loss
Alkalosis - diuretics, vomiting, nasogastric suction, barter’s / gitelman’s syndrome
Acidosis - renal tubular acidosis 1/2, ureteral diversion

20
Q

How and where do thiazides act?

A

Block NaCl reabsorption in DCT

21
Q

How and where does RTA I act?

A

Increase K secretion in CD

22
Q

How and where does RTA II act?

A

Block reabsorption in PCT

23
Q

How and where does Gitelman’s act?

A

Blocks NaCl reabsorption in DCT

24
Q

How and where does Bartter’s act?

A

Block NaKCl transporter reabsorption in TALH

25
Q

How and where do Furosemides act?

A

Block NaKCl transporter reabsorption in TALH

26
Q

What causes hypertensive hypokalemia?

A 
Hyperreninemia
Praimary hyperaldosteronism (Conn's syndrome)
Cushing's syndrome (Glucocorticoid excess - acts like aldosterone)
Congenital adrenal hyperplasia (excess aldosterone precursors)
27
Q

What are the signs of hypokalemia?

A

Prominent U wave
Tachyarrythmias
Nephrogenic diabetes insipidus

28
Q

What is the treatment of hypokalemia?

A 
Potassium replacement (KCl or KPO4)
Potassium sparing diuretics
29
Q

What are the types of potassium sparing diuretics?

A

Epithelial Na Channel (ENAC) inhibitors - Amiloride, Triamterene
Mineralocorticoid antagonists - Spironolactone, Eplerenone

Nephrology (18 decks)

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