POTASSIUM BALANCE Alan C. Pao, M.D. Division of Nephrology Cell:

Why devote 2 lectures to K+? Disorders of plasma K+ affect cell functions Disorders of K+ affect muscle function and nerve conduction Disorders of K+ cause death - often sudden

GOALS Tissue distribution of K+ Urinary excretion of K+ Clinical disorders of K+ balance and treatment

Diffusion of K+ out of cell sets up negative charge

Sodium channels begin to open Na-K ATPase resets Action potential

GOALS Tissue distribution of K+ Urinary excretion of K+ Clinical disorders of K+ balance and treatment

Na/K ATPase can be stimulated Insulin Catecholamines

ACID BASE BALANCE Can affect the serum potassium level

Alkalosis shifts K in to cells Cell K+K+ H+H+ OH - added Extracellular Fluid

Conditions that shift K+ into cells Insulin administration Stress reaction Alkalosis

GOALS Tissue distribution of K+ Urinary excretion of K+ Clinical disorders of K+ balance and treatment

ALDOSTERONE Na+ K+ H+ HCO

Hypokalemia- Low Plasma Potassium Hyperkalemia- High Plasma Potassium

HYPOKALEMIA Definition is serum K+ < than 3.5 mEq/L Decreased intake Shifting of K+ into cells Increased renal losses Increased stool losses

Poor oral intake of potassium Starvation Vomiting Malabsorption Clay

Conditions that shift K+ into cells Insulin administration Stress reaction Alkalosis

CASE 20 y.o. Asian male seen in ER for one day of acute onset muscle weakness –Leg > arm weakness –Thigh > calf ms weakness –Could not get out of bed and cannot walk –No muscle aches Over past 3 months: 35 pound weight loss, attributed to boxing training regimen Eats pasta frequently for training regimen

FH father with hyperthyroidism No PMH, No Meds No EtOH, tobacco, IVDA

VS T 36.4 P 91 BP 125/60 RR 18 Neuro exam a and o x 4 CN 2-12 intact Motor grip 4/5, elbow flexion/extension 4/5 Shoulder abduction/adduction 4/5 Motor dorsiflex/plantar flex 3/5 Knee extension/flex 4/5 Hip flexion/extension 3/5 Sensory grossly intact Reflexes 1+ throughout

Labs CSF normal CK 617 Utox neg TSH <

Increased stool losses Diarrhea Laxative abuse Tumors that cause K+ secretion into stool

Increased Renal Losses Diuretic medications

ALDOSTERONE Na+ K+ H+ HCO

Increased Renal Losses Diuretic medications Mineralocorticoid excess Amphotericin B Hypomagnesemia

ALDOSTERONE Na+ K+ H+ HCO

CASE 63 year old male with severe HTN Serum potassium of 3.0

CASE 63 year old male with severe HTN Serum potassium of 3.0 Serum bicarbonate of 30

ALDOSTERONE Na+ K+ H+ HCO

CASE 63 year old male with severe HTN Serum potassium of 3.0 Serum bicarbonate of 30 Renin level is suppressed Aldosterone level elevated

ALDOSTERONE Na+ K+ H+ HCO

ALDOSTERONE Na+ K+ H+ HCO RENIN

Treatment of Hypokalemia Find the underlying cause and treat it Stop the clay, stop the laxatives, reduce the diuretics etc. Administer K+ orally or intravenously Replace magnesium

HYPERKALEMIA Definition is serum K+ > than 5.3 mEq/L Increased intake Shifting of K+ out of cells Decreased renal losses

Increased intake of K+ Oral intake such as bananas, tomatoes K+ supplements Intravenous KCL

Conditions that shift K+ out of cells Insulin deficiency Adrenergic blocking medications Acidosis Cell lysis

Decreased urinary K+ excretion Renal failure Hypoaldosteronism Potassium sparing diuretic such as spironolactone

ALDOSTERONE Na+ K+ H+ HCO3-

GOALS Tissue distribution of K+ Urinary excretion of K+ Clinical disorders of K+ balance and treatment