9 - Dyskalemias

Question 1

largest store of ICF potassium is in

Answer 1

muscle

Question 2

clinical scenarios in which ICF potassium floods ECF

Answer 2

crush injuries
rhabdomyolysis
acute liver failure
hemolysis

Question 3

3 short term causes of K uptake by cells

Answer 3

insulin
epi (beta 2)
alkalosis (less important)

Question 4

beta blockers have what effect on serum K

Answer 4

higher after ingesting K load

Question 5

urinary K is from filtered, secreted, or both?

Answer 5

secreted

Question 6

2 factors regulating renal K secretion by principal cells

Answer 6

aldosterone

distal Na delivery

Question 7

results of aldosterone action

Answer 7

lumen negativity in CCD

K and H secretion, Na reabsorption

Question 8

hypokalemic periodic paralysis

Answer 8

intermittent acute attacks of muscle weakness w/ hypokalemia

triggered by large carb meals, rest post exercise

2 forms - AD mutation in DHP sensitive Ca channel OR thyrotoxicosis

Question 9

3 possibilities for hypokalemia w/ metab alkalosis and high urine Cl

Answer 9

loop/thiazide diuretics
bartter’s syndrome
gitelman’s syndrome

Question 10

Bartter’s syndrome

Answer 10

mutation in transporters in TAL of LoH
phenotype is that of pt taking loop diuretic > dec fn of Na/K/2Cl channel

hypokalemia, metab alkalosis, absence of HTN, hypocalcemia

Question 11

Gitelman’s syndrome

Answer 11

mutation in Na/Cl cotransporter in DCT - looks like pt is on thiazide diuretics

hypokalemia, metab alkalosis, no HTN, hypercalcemia

Question 12

example of condition that can cause hypokalemia with metab alkalosis and low urine Cl

Answer 12

vomiting:
lose H from stomach > absorb bicarb in small intestine
excess plasma bicarb > overwhelms reabs in PCT > lose as NaBicarb
volume depletion > stim aldosterone > K loss, > PCT Na and Cl reabs > low urine chloride

Question 13

what is the next step in evaluating a pt w/ hypokalemia and high BP?

Answer 13

check renin and aldosterone levels

Question 14

causes of hypokalemia w/ HTN and high renin and aldosterone

Answer 14

renin secreting tumor
RAS > hypoperfused kidney keeps secreting renin regardless of volume status

both cause K wasting from aldosterone and high BP from NaCl retention

Question 15

causes of hypokalemia w/ HTN and low renin and high aldosterone

Answer 15

Conn’s syndrome - aldosterone secreting tumor
bilateral adrenal gland hyperplasia
glucocorticoid remediable aldosteronism (GRA)

Question 16

glucocorticoid remediable aldosteronism (GRA)

Answer 16

AD inheritance
crossover of aldosterone synthase and steroid 11B-hydroxylase that causes aldosterone secretion to be under control of ACTH instead of ATII

tx w/ dexamethasone to suppress ACTH

Question 17

causes of hypokalemia w/ HTN and low or normal renin and aldosterone

Answer 17

Cushing’s syndrome
Syndrome of Apparent Mineralocorticoid Excess (SAME)
Liddle’s syndrome

Question 18

SAME

Answer 18

syndrome of apparent mineralocorticoid excess
dysfunctional enzyme 11B-OHSDH that normally breaks down cortisol. extra cortisol in principal cell binds to mineralocorticoid receptor and acts like there is too much aldosterone > hypokalemia and HTN

Question 19

licorice (glycyrrhizic acid) can cause what syndrome?

Answer 19

SAME

Question 20

Liddle’s syndrome

Answer 20

mutation in Na channel (eNaC) in CD principal cell > always open
causes hypokalemia, HTN, metabolic alkalosis (looks like hyperaldosteronism)
tx: block that channel (amiloride)

Question 21

clinical presentation of hypokalemia

Answer 21

asymptomatic until nephrogenic DI due to ADH resistance

Question 22

U wave is pathognomonic for

Answer 22

hypokalemia

Question 23

tx for hypokalemia

Answer 23

give K - oral is safest, IV burns small vessels

Question 24

K rich foods

Answer 24

potatoes, beans, avocados, spinach, banana, tomato, raisin, fish

Question 25

3 causes of impaired K entry into cells resulting in acute hyperkalemia

Answer 25

``` lack of insulin - hyperglycemia pulls K rich water out of cells SYNS blockade (beta blockers) inorganic acidoses ```

Question 26

why do inorganic acidoses cause hyperkalemia but organic ones (lactic for ex) dont?

Answer 26

in organic, the anion can follow H in so K doesnt have to leave in inorganic, the anion often can't follow H in, so K is driven out

Question 27

2 main causes of chronic hyperkalemia

Answer 27

renal failure | hypoaldosteronism (includes K sparing diuretics which block aldosterone)

Question 28

2 times when you might be in a hypoaldosterone state

Answer 28

type 4 RTA | spironolactone

Question 29

hyperkalemia clinical presentation

Answer 29

depolarizes cardiac muscle - peaked T waves, loss of P wave, widened QRS, basically progressing towards sine wave / Vfib skeletal muscle weakness

Question 30

hyperkalemia tx

Answer 30

stabilize cardiac fn w/ IV calcium (doesnt fix hyperkalemia at all) shift K into cells (quick fix) - insulin+glucose, beta 2 agonist, NaBicarb (may not work in renal failure) remove K from body - diuretics, cathartic or cation exchange resin (kayexalate), dialysis

Question 31

why does high aldosterone cause alkalosis?

Answer 31

intercalated cell secretes H allowing bicarb to enter blood

Question 32

how do you differentiate bartter's from gitelman's?

Answer 32

urine calcium