Diseases of potassium regulation

Question 1

54 y/o male with acute MI

cardiac arrest

Lab 145/2.8/120/15

ECG: Vfib

1) What was cause of arrest
2) How would you treat patient

Answer 1

K+ low due to ischemic myocardium

Treatment =

1) defibrillate
2) GIve IV K and defibrillate
3) call intern

Question 2

24 y/o male with HIV/AIDS

Diarrhea several days

145/2.6/120/14

urine K < 10 mEq/d

workup?

what would you say if urine K was 80 mEq/d

Answer 2

Workup =

1) low serum K
2) diarrhea
3) low urine K
4) extrarenal problem (GI problem) and acidotic with diarrhea so hypokalemia due to diarrhea

Trematnet

1) treat the diarrhea
2) give him K

if patient had high urine K

1) look at his acid/base status

if acidotic = look for RTA

if normal pH = magnesium

Question 3

16 y/o woman with DKA

136/6.5/95/6

Glucose 650

Metabolic acidosis

what is cause of hyperkalemia

how would you treat high K

Answer 3

1) cause = insulin deficiency causing hyperglycemia –> acidosis –> inability to move K+ from ECF to intracellular –> hyperkalemia
2) treatment = treat the DKA with insulin - lower serum K to reasonable leve

then become hypokalemic and treat

Question 4

16 y/o woman with DKA

20 years later

developed CKD due to diabetes

meds = insulin, BB, ACEI, HCTZ

Labs = 139/6.2/109/19

BUN 42, creat 1.8

Glucose = 118; Hg A1C = 6.5

what is cause of hyperkalemia

how would you treat

Answer 4

1) bb depending could be problme

ACEI = problme = lowers aldosterone levels by blocking angiotensin II

HCTZ = hypokalemic

Treatment =

1) start with urine K
2) if urine K low and GFR okay –> figur eout if sufficient aldo or no aldo
3) if no aldo, she is probably due to ACEI –> hypoaldosteronism

Question 5

Problem:

intracellular K = 3500 mEq

extracellular K = 60 mEq

Serum K = 3.5-5 mEq/L

Dietary K = 30 mEq/meal

After eating why doesn’t extracellular K go from 60 –> 90 and serum K from 4–> 6 mEq/L

Answer 5

hyperkalemic arrhythmia and die.

not usu die immediately from eating such significant dietary K+

Question 6

Internal K balance controlled by 3 hormones

Answer 6

1) insulin = insulin moves K+ from ECF to ICF by activ Na/K transporter
2) catecholamines = B2 adrenergic receptor =moves K+ from ECF to intracellular
3) aldosterone

Question 7

what is the diff between nonselective bb vs. selective bb

Answer 7

nonselective bb (propranolol) prevents K movment

selective bb (metoprolol) does not prevent K movement

Question 8

Answer 8

1) insulin binds receptor
2) activ Na/H antiporter bringing Na in
3) activ Na/K transporter to bring K from ECF to ICF

Question 9

what is importance of external K balance

Answer 9

what you eat you gotta poop or pee or

you would blow up (salt) or die (K)

Question 10

GFR = ___ (minor/major) player

cortical collecting tubule = ___ (important or not)

Kidney __ and ___ K in contrast to Na, water, Ca, PO4 where there is just reabsorption

Answer 10

1) minor until GFR very low
2) important
3) reabsorbs and secretes

so urinary K+ depends on K+
secretion in CCT

Question 11

Division of renal tubules

1) what % of filtered K load is excreted
2) proximal tubule affects K how
3) descending loop of Henle affects K how
4) ascending limb of henle affects K how
5) CCT affects K how
6) MCT and PCT affect K how

Answer 11

1) K excreted = 50%
2) prox tubule reabosrbs 50% of filtered load at end of PCT
3) 120% K+ added by end of descending loop
5) at ascending limb 15-20% leftover after reabs
4) K+ now at 120% due to secretion
5) after K+ reabsorption, K+ at 30% in urine

Question 12

Channels in ascending limb of Henle

Answer 12

1) Na/K/2Cl for reabsorption of K+
2) ROMK provides constant secretion of K+ in for Na/K/2Cl

Question 13

Channels in CCT

Answer 13

1) ENaC brings Na from lumen into cell
2) Na/K atpase pumps Na out and bring K in
3) outward rectifying K+ for leak of K+ into lumen (channel blocked by Mg)

Question 14

Question 15

CCT is sensitive to which hormone

Diseases which cause hypomagesiumemia also imply…

Answer 15

Aldosterone via MR receptor

low K+ bc remove block on ROMK channel

Question 16

Approach to determine cause of hypokalemia

3 causes of low serum K

Answer 16

1) spurious (high WBC count) = WBC > 100,000 = NOT SIGNIFICANT
2) decr TOTAL body K = decr intake OR incr loss (GI vs renal)
3) transcellular shift (stress)

Question 17

2 causes of low serum K by decr to body K

Answer 17

1) decr intake
2) incr loss = GI or renal loss

___

Question 18

if you have low TB K and low urine K < 20 meq/L what could you have

chronic

___

method to approach

Answer 18

EXTRARENAL PROBLEM =

1) if in metabolic acidosis (diarrhea= causes bicarbonate loss)
2) if in normal pH (decr dietary intake)

____

1) if no acid/base disorder, decr intake
2) if metabolic acidosis = GI loss

Question 19

if you have low TB K and high urine K > 40 mEq what could you have

CHRONIC

Answer 19

RENAL PROBLEM = look at CCT

1) metabolic alkalosis - aldosterone drives K+ and H+ secretion; moving H+ out of cell
2) normal pH ( low Mg)
3) metabolic acidosis (DKA, RTA)

____

if no acid base disorder = mg despletion

if metab acidosis = RTA type 1 or 2

if metab alkalosis = hyperaldosteronism (primary vs secondary) = K+ and H+ out of cell

Question 20

what could you have if you have low total body K, metabolic alkalosis (urine K > 40 meQ/L) and urine chloride high >20mEq/l)

Answer 20

1) if low BP = Bartter’s or Gittelman’s S
2) if high BP = primary aldosterone deficiency or cushing’s syndrome

Question 21

what could you have if you have low total body K, metabolic alkalosis (urine K > 40 meQ/L) and urine chloride < 20 mEq/L)

Answer 21

diuretics

Question 22

ECG changes with hypokalemia

Answer 22

As K+ decr, ECG becomes flatter

but no relationship btwn level of serum K+ and ECG abnormalities because normal ECG can rapidly jump to most severe ECG

Question 23

causes of transcellular shift (decreasing serum K+)

acute

Answer 23

1) catechoalmine excess = B2 AR
2) medication = b2AR agonists

3) Physiology = stress (chest pain and substernal MI, acute asthma = hypoxic and hypercarbic= sudden death
alcohol or drug withdrawal)

4) Insulin excess (rare)

Question 24

Hypokalemia –> decr total body K+ –> extrarenal loss (urinary K+ < 20)

causes of metabolic acidosis

Answer 24

1) GI loss
2) diarrhea
3) laxative abuse
4) GI fistulas

Question 25

Hypokalemia –> decr total body K+ –> extrarenal loss (urinary K+ < 20)

normal acid base

Answer 25

1) decr intake
2) cutaneous or GI loss
3) laxative abuse
4) geophagia

Question 26

Hypokalemia –> decr total body K+ –> extrarenal loss (urinary K+ < 20)

metabolic alkalosis

Answer 26

1) GI loss
2) laxative abuse
3) congenital chloride losing diarrhea

Question 27

Hypokalemia –> decr total body K+ –> renal loss (urinary K+ > 20)

variable acid base balance

Answer 27

1) recovery phase of ATN
2) postobstructive diuresis
3) Mg depletion
4) leukemia
5) drugs
6) cisplatin or penicillin large dose

Question 28

Hypokalemia –> decr total body K+ –> renal loss (urinary K+ > 20)

metabolic acidosis

Answer 28

1) RTA
2) carbonic anhydrase inhib
3) DKA

Question 29

Hypokalemia –> decr total body K+ –> renal loss (urinary K+ > 20) –> metabolic alkalosis

low urinary chloride (< 10 mEq/L)

Answer 29

1) diuretics
2) vomiting/nasogastric drainage
3) chloride losing diarrhea
4) cystic fibrosis

Question 30

Hypokalemia –> decr total body K+ –> renal loss (urinary K+ > 20) –> metabolic alkalosis

high urinary chloride (> 20 mEq/L)

normotension

Answer 30

1) diuretics
2) severe K+ depletion
3) bartters vs gittelman

Question 32

major consequences of hypokalemia

Answer 32

1) neuromuscular = weakness, paralysis, resp distress from diaphragm paralysis
2) cardiac

Question 33

Approach to treating hypokalemia ALWAYS

Answer 33

1) reverse correctable causes
2) stop diuretics
3) correct magnesium

Question 34

Approach to treating hypokalemia additionally if symptomatic (arrhythmia +/- digitalis, paralysis, or weakness)

Answer 34

1) IV replacement up to 40 mEq/hr–> if give orally limited dose, if give IV limited by rate
2) continuous ECG monitoring and serum K+ monitoring

Question 35

Approach to treating hypokalemia additionally if asymptomatic with metabolic acidosis (diarrhea or RTA)

Answer 35

1) K+ citrate or K+ bicarbonate

Question 36

Approach to treating hypokalemia additionally if asymptomatic with metabolic alkalosis or normal pH

1) normotensive
2) Hypertensive

Answer 36

1) KCl or volume replacement
2) consider K+ sparing diuretic

Question 37

3 causes of high serum K+

Answer 37

1) spurious (incr platelet count) = pseudohyperkalemia
2) decr renal K+ excretion (GFR < 20 = exogenous vs. endogenous K vs meds)
3) transcellular (DKA or hyperglycemia)

Question 38

if high serum K with high GFR > 20 mL/min

with low aldosterone

causes?

Answer 38

PROBLEM WITH RAAS

1) low renin = DM
2) high renin = adrenal insufficiency

Question 39

if high serum K with high GFR > 20 mL/min

with high aldosterone

CAUSES?

Answer 39

with low urine Na = decr Na delivery

with high urine Na = drugs, PHA

Question 40

what happens if you get a spurious cause of high serum K

Answer 40

1) repeat serum K
2) plasma rather than serum K because platelets haven’t time to coagulate (thrombocytosis)

Question 41

What is the first test you would order in a patient with hyperkalemia?

Answer 41

ALWAYS REPEAT THE ECG

if ecg normal, continue workup
if ecg abnormal, treat first and workup next

Question 42

ECG consequences of hyperkalemia

Answer 42

peaking of T wave and widening of segment (PR, QRS, QT, etc.)
but not linearly related so can jump stages from normal to abnormal ECG easily

Question 43

Approach to treating hyperkalemia

if ECG changes present,

Answer 43

1) acutely give Calcium right away = stabilize the membrane = lasts for 15 min

2) sodium bicarbonate to push into ICF (lasts for 1 hr)
3) insulin and glucose
4) albuterol nebulizer
5) K exchange resins (K-xcylat) exchanges K for Na in the gut

6) DIALYSIS

Question 44

Acute causes of hyperkalemia (transcellular shift)

Answer 44

1) inadequate insulin response = diabetes (type 1 or type 2)
2) medications = nonselective BB and take large dose of K+

3) ischemic or dead body part = rhabdomyolysis or interstitial/peripheral vascular arterial insufficiency
dumping of K+ into cell from intracellular to ECF

Question 45

Chronic causes of hyperkalemia

major problem is…NOT

urine K is usu…

Answer 45

1) high K+ dietary intake RARELY SUFFICIENT
2) must be renal excretory defect as well

major problem is K secretion by the CCT NOT GFR until ESRD
Urine K is usually (but not always low < 20 mEq/L