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Flashcards in Potassium metabolism - Showkat Deck (29):
1

Where is the majority of potassium in the body?

ICF - muscle

2

What routes excrete potassium?

Renal (90%)
GI (10%)

3

Where is potassium excreted in the nephron?

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

4

Where is potassium reabsorbed in the nephron?

TALH- NaK2Cl and paracellularly

5

What factors affect potassium secretion in the distal tubule?

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

6

What are causes of decreased renal potassium secretion?

Renal failure
Distal tubular dysfunction
Decreased distal tubular flow
Hypoaldosteronism

7

What are causes of increased renal potassium secretion?

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

8

What factors affect internal potassium balance?

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

9

How do changes in extracellular pH produce affect K?

Reciprocal shifts in H and K

10

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

Acidosis - Hyperkalemia
Alkalosis - Hypokalemia

11

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

Potassium would leave the cell via solvent drag

12

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

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

13

What are three major causes of potassium concentration?

Intake
Excretion
Internal Distribution

14

What are causes of internal redistribution that would produce hyperkalemia?

Insuline deficiency
Beta2-Adrenergic blockade
Hypertonicity
Acidemia
Cell lysis

15

What are signs of hyperkalemia?

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

16

What is the treatment for hyperkalemia?

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

17

What is the quickest and slowest acting treatment of hyperkalemia?

Quickest - Calcium
Slowest - Resin

18

What are causes of internal redistribution that would produce hypokalemia?

Insulin excess
Catecholamine excess (epinephrine)
Alkalemia
Cell proliferation

19

What causes normotensive hypokalemia?

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

20

How and where do thiazides act?

Block NaCl reabsorption in DCT

21

How and where does RTA I act?

Increase K secretion in CD

22

How and where does RTA II act?

Block reabsorption in PCT

23

How and where does Gitelman's act?

Blocks NaCl reabsorption in DCT

24

How and where does Bartter's act?

Block NaKCl transporter reabsorption in TALH

25

How and where do Furosemides act?

Block NaKCl transporter reabsorption in TALH

26

What causes hypertensive hypokalemia?

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

27

What are the signs of hypokalemia?

Prominent U wave
Tachyarrythmias
Nephrogenic diabetes insipidus

28

What is the treatment of hypokalemia?

Potassium replacement (KCl or KPO4)
Potassium sparing diuretics

29

What are the types of potassium sparing diuretics?

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