Potassium Metabolism

Question 1

Where is most potassium in the body located?

Answer 1

Intracellular compartment = 98%, most in muscle

Question 2

Regarding the nephron, where is most potassium reabsorbed?

Answer 2

Proximal convoluted Tubule (65%)

Question 3

Three fundamental causes of hyperkalemia?

Answer 3

Decreased renal excretion, Excessive intake, Internal redistribution

Question 4

What is the only part of the tubule system where K is secreted?

Answer 4

Distal Tubule

Question 5

Decreased renal excretion causes?

Answer 5

Acute or chronic renal failure
Decreased distal tubular flow
Distal tubular dysfunction
hypoaldosteronism

Question 6

Hyperkalemia manifests as what on an EKG?

Answer 6

Initially, Peaked T wave.
As it worsens….QRS widens
…P wave is absent
…sine wave (tachycardia)

Question 7

Hyperkalemias effect on the heart?

Answer 7

EKG changes, cardiac conduction defects, arrhythmias

Question 8

Hyperkalemia will manifest clinically in what way?

Answer 8

Heart problems and muscular problems

Question 9

Treatment of hyperkalemia

Answer 9

stabilize cardiac muscle cells with IV calcium,

Lower serum K level

Question 10

What are methods of lowering serum K level in hyperkalemia?

Answer 10

Move K inside the cell with:
Insulin, B antagonists, Bicarbonate
Or, Move K outside the body:
Diuretics, resin, dialysis

Question 11

What is the main B antagonist?

Answer 11

Albuterol

Question 12

Causes of hypokalemia

Answer 12

Decreased intake, increased excretion, internal redistribution

Question 13

Hypokalemia in hypertensive disorders, what three hormones are associated with this>

Answer 13

Renin, aldosterone, gluccocorticoid

Question 14

How does potassium come into cells in the Thick ascending loop of Henle?

Answer 14

Through NK2C pumps. Then flows back out to the lumen to be re-used and to maintain a gradient for the paracellular infusion of other positivel charged molecules

Question 15

What role does aldosterone play in the movement of sodium in the convoluted tubule?

Answer 15

Aldosterone stimulates the NaKATPase pump, stimulates the ROMK channel which pushes potassium back into the lumen, stimulates the Na epithelial channel which provides Na for the NaKATPase pump

Question 16

How important is the concept/phenomenon of distal sodium delivery to the secretion ok K back to the lumen.

Answer 16

VERY IMPORTANT. Basically, distal sodium delivery creates an electronegative lumen to draw sodium out of teh cell and into the lumen.

Question 17

Three major factors affecting the internal balance of potassium?

Answer 17

1. ) Acid-Base disturbance: changes in extracellular pH leads to reciprocal shifts of H+ and Na/K. SO during extracellular alkalosis, H+ moves into the ECF and K moves inside. and vice versa
2. ) Changes in plasma tonicity. Hypertonic plasma draws water out of Intracellular fluid (solvent drag brings K with it)
3. ) Cell Lysis and ProliferationCel lysis releases K into the ECF

Question 18

What are the two categories of hypokalemia from renal loss

Answer 18

Normotensive and hypotensive

Question 19

Causes of normotensive hypokalemia/

Answer 19

Metabolic alkalosis, metabolic acidosis

Question 20

Describe the effect of aldosterone on the principle cells. What does it stimulate?

Answer 20

Stimulates the uptake of sodium from the lumen. This sodium is then used in the NaKATPase channel that aldosterone also stimulates. Also stimulates K to move through the K channel back into the lumen. THerefore, aldosterone stimulates the uptake of sodium and the excretion of K.

Question 21

Why is distal sodium delivery so imporatant in the aldo K excretion.

Answer 21

Without Na, the Na K pump cant run and the electrical gradient and concentration gradient are not established to draw K back into the lumen for excretion

Question 22

Increast distal tubular flow rate means

Answer 22

Increased K secretion

Question 23

How does insulin affect internal K balance?

Answer 23

Stimulates the Na+ H+ exchanger which brings Na into the cell to be used in the Na K ATPase.

Question 24

Three factors affecting internal sodium balance

Answer 24

Insulin, Epinephrine, Plasma potassium conc.

Question 25

How does epinephrine effect K balance

Answer 25

Influences Beta receptor which stimulates NaK ATPase

Question 26

Describe the behavior of K during metabolic alkalosis.

Answer 26

Metabolic alkalosis occurs when Extracellular pH is high, low H+. This means H moves out of cell to counter the rise in pH and K moves into the cell causing Hypokalemic conditions.

Question 27

K in metabolic acidosis

Answer 27

In metabolic acidosis, low bicarb and high H in ECF, H moves in, K moves out….hyperkalemic conditions.

Question 28

How does hypertonicity in plasma affect K?

Answer 28

Hypertonicity in the plasma is basically the same as high plasma osmolarity….it draws out water from inside the cells into the plasma, K comes with the water….solvent drag.

Question 29

How does hypotonicity of plasma affect K

Answer 29

Opposite of hyper

Question 30

Hyperglycemia creates what?

Answer 30

Hyperkalemia…creates inc plasma tonicity which draws water and plasma out of cells.

Question 31

EKG manifestations of hyperkalemia?

Answer 31

First- peaked T wave, Later- Wide QRS, Last Sine wave

Question 32

Signs of hyperkalemia

Answer 32

EKG changes, cardiac conduction defects, arrhythmias, weakness

Question 33

Hyperkalemia treatment?

Answer 33

Stabilize cardiac muscles with calcium, lower serum K, move K inside cells (insulin, B agonist, Bicarbonate), Move K out of body (Diuretics, Resin, Dialysis

Question 34

Hypokalemai causes?

Answer 34

Decreased intake, External losses- GI, cutaneous, renal Internal redist like insulin excess, catecholamine excess, alkalemia, cell prolif

Question 35

EKG manifestations of hypokalemia

Answer 35

Flat T wave, Prominent U, Depresssed ST