Jan9 M2-Potassium Pathophysiology

Question 1

hyperK and hypoK effect on resting potential

Answer 1

hyperK: depol (resting potential more positive)
hypoK: hyperpol (resting potential more negative)

Question 2

electrical effects of hyperK on the heart + ultimate effect (less or more excitable)

Answer 2

• sustained gradual depolarization
• inactivation of Na channels
• *less excitable even though closer to threshold bc Na channels inactivated

Question 3

hyperK on ECG (step by step)

Answer 3

peaked T wave, widened QRS, loss of P wave, sine wave, V fib

Question 4

3 causes of hyperkalemia

Answer 4

impaired cell entry, increased cell release, reduced urinary excretion

Question 5

key points in hyperK

Answer 5

almost all cases involve decreased GFR and are multifactorial

Question 6

why can have hyperK in heart failure

Answer 6

volume contraction with decreased GFR

Question 7

hormonal problem that can cause hyperK and 3 causes to that

Answer 7

hypoaldosteronism (1. primary adrenal insufficiency 2. ACEi 3. NSAIDs bc inhibit PGs’ effect on renin release)

Question 8

drug that can cause hyperK

Answer 8

K sparing diuretics

Question 9

can high K diet cause hyperK? yes no and why

Answer 9

no bc aldo turned on and K excreted normally

Question 10

why does high K diet not cause high Na reabso

Answer 10

when euvolemic, RAAS is off (aldo is on because detects K but renin and therefore AT2 are off so AT2 doesn’t promote Na reabso at PCT)

Question 11

hyperK cause related to not enough cell entry

Answer 11

insulin deficiency in hyperglycemia or uncontrolled diabetes

Question 12

hyperK cause related to too much excretion from cells

Answer 12

rhabdomyolysis (muscle breakdown so K from these cells is released)

Question 13

why can have false positive hyperK

Answer 13

when blood sample is hemolyzed (cells in it lysed)

Question 14

history of patient with hyperK

Answer 14

• ask for CKD!!! (GFR!!), diabetes, adrenal insufficiency

- drugs taken (ACEi, ARB, K-sparing like spironolactone)

Question 15

labs in hyperK patient

Answer 15

Cr, urea (GFR!!), glucose, electrolytes, bicarb

Question 16

important test to do in hyperK patient

Answer 16

ECG

Question 17

drugs that contribute to hyperK (4 types)

Answer 17

• ACEi and ARBs
• NSAIDs
• cyclosporine (reduce renin release)
• all K sparing (ENac blockers or MRAs)

Question 18

how diabetes affects renin release

Answer 18

reduced renin release

Question 19

symptoms of hyperK + what kind of arrhythmia

Answer 19

weakness, feeling faint, arrhythmia (brady)

Question 20

summary of 3 causes to hyperK

Answer 20

low GFR
low aldo (drug, adrenals)
K shift out (insulin, rhabdo)

Question 21

3 parts of hyperK treatment

Answer 21

• protect the heart
• shift the K in the cells
• excrete the K

Question 22

hyperK treatment: how to protect the heart and when

Answer 22

if peaked T waves, give IV Ca gluconate. Ca increases AP threshold

Question 23

hyperK treatment: how to shift K in the cells (2)

Answer 23

• IV D5W + insulin

- inhaled beta-2 agonist (salbutamol)

Question 24

hyperK treatment: how to excrete the K + this part of the treatment depends on what

Answer 24

oral K exchange resin (exchanges K with Ca)
loop diuretic if volume overloaded
NS if volume deplete

Question 25

other considerations in hyperK treatment (think of causes)

Answer 25

dietary review
control diabetes
stop the meds (ACEi, K-sparing diuretics, NSAIDs, etc.)

Question 26

does IV bicarb decrease K levels? what’s the basis for that

Answer 26

no. (but would think yes because H (out) K (in) exchanger in alpha intercalated cells would work less and keep more K out)

Question 27

if you’re on ACEi or ARB or NSAID, how much aldo secretion after K intake

Answer 27

some secretion bc adrenals react to K level

Question 28

channels stimulated by aldo (or synthesized to its effects)

Answer 28

• ENac, ROMK and Na-K ATPase of principal

- H (out) K (in) ATPase exchanger in alpha int.

Question 29

ECG changes in hypoK

Answer 29

U wave formation, T wave flattening, arrhythmia but less than hyperK

Question 30

effect of hypoK on muscles

Answer 30

muscle weakness, cramping and pain (myalgias)

rhabdomyolysis and paralysis if severe

Question 31

most common cause of hypoK + other causes

Answer 31

• diuretics (distal flow of Na increases K secretion)
• high aldo
• chemo (Fanconi Syndrome: less PCT reabso)
• GI losses
• black licorice (acts like aldo)

Question 32

hypoK symptoms

Answer 32

weakness or brady arrhythmia

Question 33

3 conditions or states where hypoK is caused by urinary loss (and increased distal Na flow)

Answer 33

• primary hyperaldo
• RAS
• diuretics

Question 34

most common GI tract loss cause of hypoK and why

Answer 34

diarrhea (bc GI secretion with highest K)

Question 35

does alkalosis cause hypoK. (this question is different from ‘‘does bicarb reduce K’’) if yes how

Answer 35

yes. alkalosis: bicarbonaturia. bicarb enters the CCD cells and H (out) K (in) ATPase works less so that H stays inside with bicarb

Question 36

history in hypoK

Answer 36

hyperaldo? diuretics? diarrhea?

Question 37

how to differentiate between renal vs extra-renal K loss

Answer 37

• if renal (urine K spot>15 and 24hr>30)

- if extra-renal (diarrhea): low urine K

Question 38

hypoK treatment

Answer 38

IV or oral replacement

Question 39

very important rule in K administration

Answer 39

for a serum deficit of 1 mM, there is a K deficit of 100-150 mM (in the body). (K conc in the ICW is 140 mM)