1: Potassium

Question 1

Intracellular and extracellular K+ concentrations

Answer 1

140 and 4-5 meq/L respectively

Question 2

K+ decrease/increase by 1 meq reflects what deficit/excess respectively?

Answer 2

200-400 meq deficit, 100-200 meq excess

Question 3

Symptoms of K+ imbalance

Answer 3

Related to AP generation issues in muscles: cramps, muscle weakness/ paralysis starting in legs, EKG changes, arrhythmias

Question 4

EKG changes in hypoK

Answer 4

PR prolongation, ST depression, flattened or inverted T waves, U waves, QRS widening

Question 5

EKG changes in hyperK

Answer 5

PR prolongation, elevated T waves, widened QRS, weird sine wave type shaped QRS

Question 6

HyperK does what to membrane potential? How can this be mitigated?

Answer 6

Depolarizes. Hypercalcemia -> inc threshold potential (give Ca).

Question 7

How are K+ and pH interconnected?

Answer 7

Met acidosis -> release K+ from cells while HCl is buffered into cells. Treat with bicarb. Opposite is true (K+ enters cells/H+ leaves in alkalosis)

Question 8

What causes K+ to move into cells?

Answer 8

Insulin, catecholamines

Question 9

Potassium elimination route, reasons for concern

Answer 9

Major route: kidney -> urine. Minor: stool and sweat, if clinically important = pathologic.

Question 10

Effect of aldosterone onK+ secretion by principal cells

Answer 10

Increases K+ secretion

Question 11

Hypokalemia turns on reabsorption of K+ in ___ (kidney part) by ___ (cell type)

Answer 11

Collecting duct, intercalated cells

Question 12

What is the interaction of K+ and Mg?

Answer 12

hypomagnesemia -> affects #K channels -> hypokalemia

Question 13

HypoK: need to determine loss through GI or urine (or pH issue). How?

Answer 13

Hx: laxative, vom, diarrhea. 24 hr K+: if low, loss is not from kidney. Kidney should be able to dec K+ excr to 25-30 meq/24 hrs.

Question 14

HypoK complications

Answer 14

Muscle-related, rhabdomyolysis, renal dysfx (loss of conc ability, inc NH3/4+ prod/excr), hypertension

Question 15

Causes of hyperkalemia

Answer 15

Inc intake, kidney disease -> dec excretion, shift from intra to extracellular

Question 16

What saves us from hyperkalemia when dietary intake is high?

Answer 16

Rapid shift into skeletal muscle and hepatocytes thanks to insulin and beta-adrenergic receptors. Also inc K+ -> aldosterone release -> excretion w/in 6-8 hrs

Question 17

Causes of K+ shift out of cells

Answer 17

Muscle/tissue breakdown, insulin deficiency, metabolic acidosis, drugs (succinylcholine, b-blockers, digoxin)

Question 18

Causes of dec urinary excr of K+

Answer 18

renal failure (most common), dec ECV -> dec distal flow, hypoaldosteronism

Question 19

What should you look for if K+ = 6.5+ w/o EKG changes?

Answer 19

Pseudohyperkalemia

Question 20

What conditions potentiate K+ toxicity?

Answer 20

Hyponatremia and acidemia

Question 21

Steps in hyperK treatment

Answer 21

1. Antagonize K+ effects (IV Ca) 2. shift K+ into cells (Gluc/insulin/NaHCO3, 3% NaCl if hypoNa) 3. Remove excess K+ (loop diuretics, dialysis, Kayexalate: cation exchange resin)

Question 22

Usual culprits (2) in K+ imbalance

Answer 22

adrenal glands (mineralcorticoids) and kidneys