Potassium Metabolism - Showkat

Question 1

Where does most potassium reside in the body?

Answer 1

Muscle, also liver, RBCs, bone

Question 2

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

Answer 2

PCT

Question 3

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

Answer 3

PCT, thick ascending limb, CD

Question 4

How is K reabsorbed in the thick ascending limb?

Answer 4

Na/K/2Cl transporter using sodium concentration gradient

Question 5

How is K reabsorbed in the CD?

Answer 5

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

Question 6

What does increased distal sodium delivery do to potassium levels?

Answer 6

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

Question 7

What are all of the effects of aldosterone on potassium?

Answer 7

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

Question 8

Hyperaldosteronism leads to…

Answer 8

Hypokalemia

Question 9

Hypoaldosteronism leads to…

Answer 9

Hyperkalemia

Question 10

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

Answer 10

Plasma K concentration
Insulin
Epinephrine

Question 11

How does insulin influence K movement in the kidney?

Answer 11

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

Question 12

How does epinephrine influence K movement in the kidney?

Answer 12

It activates the Na/K ATPase through the beta receptor

Question 13

Why are diabetic (DM) patients hyperkalemic?

Answer 13

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

Question 14

Why do beta blockers have the ability to cause hyperkalemia?

Answer 14

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

Question 15

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

Answer 15

Metabolic

Question 16

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

Answer 16

Mineral acids

Question 17

Alkalosis causes this change in K

Answer 17

hypokalemia

Question 18

Acidosis causes this change in K

Answer 18

hyperkalemia

Question 19

How does plasma tonicity affect potassium balance?

Answer 19

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

Question 20

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

Answer 20

Renal failure patietns

Question 21

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

Answer 21

renal failure, decreased distal tube flow, hypoaldosteronism

Question 22

What are some examples of internal redistribution that cause hyperkalemia?

Answer 22

Insulin deficiency
Beta blockers
Hypertonicity
Acidemia
Cell lysis

Question 23

What is the EKG manifestation of hyperkalemia?

Answer 23

Widened QRS

No P wave

Question 24

What are the S/S of hyperkalemia?

Answer 24

EKG changes
Arrhythmia
Neuromuscular changes - weakness, ileus

Question 25

How do you stabilize cardiac muscle cells during severe hyperkalemia?

Answer 25

IV Calcium

Question 26

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

Answer 26

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

Question 27

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

Answer 27

Diuretics Resins? Dialysis

Question 28

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

Answer 28

GI

Question 29

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

Answer 29

GI loss Cutaneous loss Renal loss

Question 30

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

Answer 30

Insulin excess Catcholamine excess Alkalemia cell proliferation

Question 31

Gitelman's syndrome mechanism

Answer 31

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

Question 32

Bartter's syndrome mechanism

Answer 32

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

Question 33

What are two hormones that can lead to hypertensive hypokalemia?

Answer 33

Renin -renal artery stenosis or tumor secretion Aldosterone (from tumor - Conn's syndrome) from adrenal hyperplasia Diuretics do same thing pretty much

Question 34

What are S/S of hypokalemia?

Answer 34

``` Muscle weakness and rhabdo EKG changes Tachyarrythmias Ilus Nephrogenic diabetes insipidus ```

Question 35

What are the EKG manifestations of hypokalemia?

Answer 35

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

Question 36

What is the treatment for hypokalemia?

Answer 36

K replacement oral or IV Also, K-sparing diuretics, usually only for chronic hyper-K

Question 37

Which diuretics are potassium-sparing?

Answer 37

Aldosterone receptor antagonists (aka mineralocorticoid antagonists) -Amiloride, triamterene ENaC inhibitors - Spironolactone - Eplerenone

Question 38

What are the two major determinants governing potassium secretion?

Answer 38

Serum aldosterone | Distal sodium delivery