Potassium Metabolism

Front 1

Importance of Potassium

Back 1

Resting membrane potential is maintained by potassium gradient
Hypo- or hyperkalemia can result in fatal cardiac arrhythmias, by altering conduction in cardiac muscle.
Hypo- or hyperkalemia may result in muscle weakness or even paralysis.

Front 2

Regulation of K homeostasis

Back 2

Cellular distribution
Renal excretion
GI excretion

Front 3

Major Regulators of Cellular K distribution

Back 3

Insulin
Catecholamines
Acid-Base status

Front 4

Insulin and Potassium

Back 4

Insulin binding to its receptor causes hyperpolarization of cell membrane which facilitates K uptake. It also activates Na-K-ATPase

Front 5

Catecholamines

Back 5

Beta agonists. increase cAMP leading to hyperactive channels Na K

Front 6

Acid Base Status

Back 6

adding H ions causes release of K and uptake H.

Front 7

Major cell regulating potassium in the kidney

Back 7

principal cells in the CD

Front 8

Principal cells

Back 8

Na K atpase on basement
K channels on both sides
Na channel on lumen side
electroneg lumen will cause K excretion

Front 9

Aldosterone and principal cells

Back 9

promotes the insertion of more K Na channels on the lumen side and enhances more Na K ATPases to basement side. resulting in more K secretion into urine and increased urinary Na absorption

Front 10

Determinants of renal K secretion

Back 10

Mineralocorticoid activity
Distal delivery of Na (eg Lasix)
Tubular flow rate (eg oliguric ATN)
Total body K

Front 11

increased sodiem in distal tubules causes

Back 11

increased K secretion leading to hypokalemia

Front 12

Increased K ( hyperkalemia) leads to

Back 12

increased K exretion into the lumen in the kidneys

Front 13

Urinary Flow rate incr

Back 13

kidney cannot secrete pure H2O, has to put electrolytes in urine so you incr K excretion

Front 14

Sx of Hypokalemia

Back 14

Muscle weakness, even paralysis
Cardiac arrhythmias
Rhabdomyolysis
Renal manifestations – impaired concentrating ability causing polyuria
Ileus
Hyperglycemia

Front 15

Hypokalemia

Back 15

Muscle weakness, even paralysis (secondary to depolarization)
Cardiac arrhythmias (ventricular fibrillation, standstill)

Front 16

Tx of Hypokalemia

Back 16

discontinue diuretics, supplement K, monitor ECG.

Asymptomatic- K salts, KCl vol replacement. Kcitrate can be used in acidosis too.

Front 17

Hyperkalemia

Back 17

incr dietary K, renal failure, k sparing Diuretics, acidosis, cell lysis, B blocker, digitalis overdose

Front 18

Sx of Hyperkalemia

Back 18

Muscle weakness, even paralysis (secondary to depolarization)
Cardiac arrhythmias (ventricular fibrillation, standstill)

increased amplitude of T wave w/ decr qtr interval. widening of qrs complex, decr p amlitude

Front 19

Treatment of Hyperkalemia

Back 19

try to shift K into cells- insulin, alkalosis and beta agonists can do it. (bicarb)

Kayexelate-orally binds K in GI tract. Start of diuresis, hemodialysis.

Ca infusion- antagonizes membrane actions of hyperkalemia. Changes normal threshold (incr) for the cell...so the hyperkalemic cell has to reach a higher threshold to fire.