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OS Renal > Potassium Metabolism - Showkat > Flashcards

Potassium Metabolism - Showkat Flashcards

1
Q

Where does most potassium reside in the body?

A

Muscle, also liver, RBCs, bone

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2
Q

Where in the nephron does the majority of potassium reabsorption take place?

A

PCT

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3
Q

In which places of the nephron does potassium reabsorption take place?

A

PCT, thick ascending limb, CD

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4
Q

How is K reabsorbed in the thick ascending limb?

A

Na/K/2Cl transporter using sodium concentration gradient

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5
Q

How is K reabsorbed in the CD?

A

ENaC allows Na in and creates a negatively charged lumen that favors K+ secretion from cell

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6
Q

What does increased distal sodium delivery do to potassium levels?

A

Increases loss through secretion due to higher relative (-) environment in lumen after na reabsorbed

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7
Q

What are all of the effects of aldosterone on potassium?

A

Increases Na+ entry into cell from ENaC
Increases Na/K output of Na and K influx
Increases number of luminal K+ channels

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8
Q

Hyperaldosteronism leads to…

A

Hypokalemia

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9
Q

Hypoaldosteronism leads to…

A

Hyperkalemia

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10
Q

What are three things that promote K movement across the membrane?

A

Plasma K concentration
Insulin
Epinephrine

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11
Q

How does insulin influence K movement in the kidney?

A

Insulin stimulates Na/H exchanger that moves Na inside. The Na leads to more Na/K ATPase activity

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12
Q

How does epinephrine influence K movement in the kidney?

A

It activates the Na/K ATPase through the beta receptor

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13
Q

Why are diabetic (DM) patients hyperkalemic?

A

Lack of insulin fails to stimulate Na/K ATPase activity, reducing the amount of K available intracellularly to be secreted

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14
Q

Why do beta blockers have the ability to cause hyperkalemia?

A

They block activity of Na/K ATPase, resulting in less K being available for secretion

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15
Q

Do metabolic or respiratory acid-base disturbances have a greater effect on K levels?

A

Metabolic

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16
Q

Does metabolic acidosis due to organic acids or mineral acids have a greater effect?

A

Mineral acids

17
Q

Alkalosis causes this change in K

A

hypokalemia

18
Q

Acidosis causes this change in K

A

hyperkalemia

19
Q

How does plasma tonicity affect potassium balance?

A

Solvent drag- osmole migration out of cell during hyperosmolarity drags K+ with it

Also, when water leaves cells, that creates a higher K concentration inside the cell that contributes to K eflux

Both result in hyperkalemia

20
Q

Hyperkalemia due to excessive potassium intake is really only possible with these people

A

Renal failure patietns

21
Q

What are some instances that would lead to hyperkalemia from decreased renal excretion?

A

renal failure, decreased distal tube flow, hypoaldosteronism

22
Q

What are some examples of internal redistribution that cause hyperkalemia?

A 
Insulin deficiency
Beta blockers
Hypertonicity
Acidemia
Cell lysis
23
Q

What is the EKG manifestation of hyperkalemia?

A

Widened QRS

No P wave

24
Q

What are the S/S of hyperkalemia?

A

EKG changes
Arrhythmia
Neuromuscular changes - weakness, ileus

25
Q

How do you stabilize cardiac muscle cells during severe hyperkalemia?

A

IV Calcium

26
Q

What treatments can be used to move K inside of cells?

A

Insulin (Na/K pump activity up thru Na/H)
B agonists (albuterol) (Na/K activity up thru B2 receptor)
Bicarbonate

27
Q

What treatments can be used to move outside of the body?

A

Diuretics
Resins?
Dialysis

28
Q

Resins are good at removal potassium from which part of the body?

A

GI

29
Q

What are some external losses of K that lead to hypokalemia?

A

GI loss
Cutaneous loss
Renal loss

30
Q

What are some internal redistributions of K that lead to hypokalemia?

A

Insulin excess
Catcholamine excess
Alkalemia
cell proliferation

31
Q

Gitelman’s syndrome mechanism

A

Na/Cl sympoter defect in collecting tubule results in too much distal Na delivery

32
Q

Bartter’s syndrome mechanism

A

defect in voltage-gated Cl- channel in thick ALH …too much potassium excretion

33
Q

What are two hormones that can lead to hypertensive hypokalemia?

A

Renin
-renal artery stenosis or tumor secretion

Aldosterone (from tumor - Conn’s syndrome)
from adrenal hyperplasia

Diuretics do same thing pretty much

34
Q

What are S/S of hypokalemia?

A 
Muscle weakness and rhabdo
EKG changes
Tachyarrythmias
Ilus
Nephrogenic diabetes insipidus
35
Q

What are the EKG manifestations of hypokalemia?

A

Flat T wave
Prominent U WAVE! (abnormal)
Depressed ST

36
Q

What is the treatment for hypokalemia?

A

K replacement oral or IV

Also, K-sparing diuretics, usually only for chronic hyper-K

37
Q

Which diuretics are potassium-sparing?

A

Aldosterone receptor antagonists (aka mineralocorticoid antagonists)
-Amiloride, triamterene

ENaC inhibitors

  • Spironolactone
  • Eplerenone
38
Q

What are the two major determinants governing potassium secretion?

A

Serum aldosterone

Distal sodium delivery

OS Renal (25 decks)

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