Disorders Of Potassium Balance And Diuretics

Front 1

Normal K levels

Back 1

98% intracellular (mostly muscle)
120-150 meq/L

Front 2

Nernst Equation

Back 2

balance between electric and chemical forces across a membrane
E=-RT/F*ln(Ki/Ko)
decr K incr electric gradient --> incr excitability
incr K decr electric gradient

Front 3

Acid-Base affect on K

Back 3

Acidemia --> K out/H out --> HyperK
inhibit distal tubular secretion of K
0.1 decr in pH incr serum K 0.5
Alkamemia --> K in/H out --> HypoK
enhances renal excr of K
0.1 incr in pH decr K 0.1 to 0.4

Front 4

Hypertonicity affect on K

Back 4

incr serum glucose w/o insulin shifts H2O and K out of cells --> hyperK

worse in HHNK than DKA b/c of K deficiency associated w/ DKA

Front 5

Insulin affect on K

Back 5

insulin stimulates Na-K-ATPase shifting K into cells
insulin administered in cases of life-threatening hyperK

Front 6

beta2 agonists

Back 6

shift K from extracell to intracell by increasing cAMP which stimulates Na-K-ATPase
beta blockers incr serum K by 0.5 meq/L

Front 7

Renal excretion/reabsorption

Back 7

88% reabsorbed
50-70% in proximal tubule
15-20% in loop of henle
enhanced secretion: incr K intake, incr Na delivery, mineralocorticoids, incr urine flow, alkalosis

Front 8

Factitious hyperK

Back 8

incr WBCs in sample lyse before analysis leading to factitious hyperK

Front 9

Increased K load

Back 9

exogenous, endogenous (rhabdomyolysis, trauma, burns, tumor lysis, hemorrhage), intra to extracell shift (acidosis, insulin def, hyperosm, dig overdose, succinylcholine, arginine or lysine infuse), hyperkalemic periodic paralysis

Front 10

Hyperkalemic Periodic Paralysis

Back 10

AD w/ 100% penetrance
mutated non-inactivating Na channel
onset in 1st year of life
attacks precipitated by EtOH, mental stress K intake, glucocorticoids, exercise
prophylax w/ thiazide diuretics, carbonic anhydrase inhibitors, mineralocorticoids

Front 11

Impaired K secretion

Back 11

acute or chronic renal fail (GFR<15)
K spareing diuretics
mineralocorticoid deficiency - addisons, idiopathic, hyporeninemic hypoaldosteronism (DM, interstitial nephritis, obstructive uropathy), adrenogenital syndrome, ACEi
Calcineurin inhibitors (cyclosporine, tacrolimus)

Front 12

clinical manifestations of hyperK

Back 12

peaked T waves, widened QRS
ascending flacid paralysis (K>7.0)
hyperchloremic acidosis

Front 13

management of acute hyperK

Back 13

Ca gluconate - antagonizes membrane affect of hyperK (never w/ dig tox)
Glucose-insulin - stimulates Na-K-ATPase
NaHCO3
Kayexalate - K binding resin
dialysis

Front 14

HypoK

Back 14

inadequate dietary intake (EtOH, anorexia)'
GI loss
extracell to intracell shift (insulin, alkalosis)
hypoK periodic paralysis

Front 15

Renal K wasting w/ HTN

Back 15

high plasma renin - incr aldo, incr renal K secretion, DDX: renal a. stenosis, malignant HTN, renin producing tumor
Low plasma renin - primary hyperaldo, exogenous mineralocorticoid, liddle's syndrome, adrenogenital syndrome, glucocorticoid excess

Front 16

Renal K wasting (normotensive)

Back 16

diuretics
RTA I/II
Mg def
DKA
non absorbing anions
Rx
Bartter's syndrome

Front 17

Liddle's syndrome

Back 17

mutation in beta-subunit of ENaC causing constitutve activation of the amiloride sensitive distal renal Na channel
AD
causes HTN, hypoK, met alk, decr renin & aldo
Tx: Na restrict or triamterene

Front 18

Bartter's syndrome

Back 18

like endogenous lasix
thick ascending limp mutations to Na-K-2Cl txp, or type II K channel, or Cl channel, or barttin
causes proximal muscle weakness, polyuria, growth retardation
Tx: K replace, K sparing diuretic

Front 19

Gitelman's syndrome

Back 19

like constitutive HCTZ
inactivating mutation in Na-Cl cotxp in DCT
present in adolescence w/ hypoK, met alk, hypoMg, hypoCa
may have intermittent cramps and muscle weakness

Front 20

clinical manifestations of hypoK

Back 20

cardiac - U waves (arrhythmia risk as T wave encroaches on QRS complex)
neuromusc - ascending muscle weak, resp fail, rhabdomyolysis, paralytic ileus
renal - polyuria, hypoK, intertitial nephritis, chronic renal insufficiency
acid-base - cannot correct met alk w/o correcting K depletion

Front 21

Osmotic Diuretic

Back 21

Mannitol
MOA - causes water to be retained in tubules promoting diuresis (opposes action of ADH)
*Na sparing (long term)
Uses - tx elevated ICP, reduce intraocular pressure, promotion of toxin excretion
AE - rapid H2O move from intra to extracellular causes acute transient ECF expand and hyponatremia --> n/v/headache, CHF complication, incr intracellular K

Front 22

carbonic anhydrase inhibitors

Back 22

Acetazolamid (Dichlophenamid, methazolamide)
MOA - inhibits CA and decr bicarb reabsorb leading to bicarb diuresis
*may cause met acid, alkalinizes urine
Uses - prophylax AMS, glaucoma (CA in eye)
AE - met acid, phosphaturia and hypercalciuria --> stone, K wasting, drowsiness (CA in CNS), paresthesias, contraindicated in liver dz (worsen hepatic encephalopathy)

Front 23

Loop diuretics

Back 23

furosemide (bumetanide, torsemide, ehtyacrynic acid)
MOA - inhibits Na-K-Cl txper in cortical and medullary thick ascending limb of loop of henle (RAPID onset)
*also have ceiling dose
Uses - first line for acute pulm edema, CHF, combo w/ HCTZ for HTN, K excrete, edema
AE - hypoK, hypoMg, hyperuricemia, incr delivery of Na to DCT --> incre K & H excrete --> met alk, hearing loss, sulfa allergy cross react, incr LDL decr HDL

Front 24

Thiazide Diuretics

Back 24

HCTZ (chlorothiazide, chlorthalidone, metolazone)
MOA - inhibits Na-Cl txper in DCT causing contraction of ECF volume
*"ceiling" diuretic
Uses - HTN, mild CHF, edema, Ca urinary stones, osteoporosis, nephrogenic DI (COUNTERINTUITIVE)
AE - Na/K/Cl/Mg depletion, uric acid retention, Ca retention, impaired insulin release, incr LDL, photosensitivity, sulfa allergy cross rxn, ineffective for GFR<40 (except metazolone (GFR<20))

Front 25

K sparing diuretics

Back 25

Spironolactone (Eplerenone) - aldo antagonists
Triamterene (Amiloride) - interferes w/ Na influx in CD
Uses - hyperaldo, HTN, diuretic induced hypoK
AE - hyperK, hyperchloremic met acid, Spironolactone: endocrine AE

Front 26

Diuretic Uses

Back 26

edema
CHF - reduce symptoms, improve exercise tolerance, no effect on dz progression
Cirrhosis - tx edema and ascites (spironolactone and furosemide)
Kidney Dz - mild dz
HTN - HCTZ 1st line
Nephrolithiasis - HCTZ
HyperCa - loop
DI - HCTZ