1: Potassium Flashcards
Intracellular and extracellular K+ concentrations
140 and 4-5 meq/L respectively
K+ decrease/increase by 1 meq reflects what deficit/excess respectively?
200-400 meq deficit, 100-200 meq excess
Symptoms of K+ imbalance
Related to AP generation issues in muscles: cramps, muscle weakness/ paralysis starting in legs, EKG changes, arrhythmias
EKG changes in hypoK
PR prolongation, ST depression, flattened or inverted T waves, U waves, QRS widening
EKG changes in hyperK
PR prolongation, elevated T waves, widened QRS, weird sine wave type shaped QRS
HyperK does what to membrane potential? How can this be mitigated?
Depolarizes. Hypercalcemia -> inc threshold potential (give Ca).
How are K+ and pH interconnected?
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)
What causes K+ to move into cells?
Insulin, catecholamines
Potassium elimination route, reasons for concern
Major route: kidney -> urine. Minor: stool and sweat, if clinically important = pathologic.
Effect of aldosterone onK+ secretion by principal cells
Increases K+ secretion
Hypokalemia turns on reabsorption of K+ in ___ (kidney part) by ___ (cell type)
Collecting duct, intercalated cells
What is the interaction of K+ and Mg?
hypomagnesemia -> affects #K channels -> hypokalemia
HypoK: need to determine loss through GI or urine (or pH issue). How?
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.
HypoK complications
Muscle-related, rhabdomyolysis, renal dysfx (loss of conc ability, inc NH3/4+ prod/excr), hypertension
Causes of hyperkalemia
Inc intake, kidney disease -> dec excretion, shift from intra to extracellular
What saves us from hyperkalemia when dietary intake is high?
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
Causes of K+ shift out of cells
Muscle/tissue breakdown, insulin deficiency, metabolic acidosis, drugs (succinylcholine, b-blockers, digoxin)
Causes of dec urinary excr of K+
renal failure (most common), dec ECV -> dec distal flow, hypoaldosteronism
What should you look for if K+ = 6.5+ w/o EKG changes?
Pseudohyperkalemia
What conditions potentiate K+ toxicity?
Hyponatremia and acidemia
Steps in hyperK treatment
- 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)
Usual culprits (2) in K+ imbalance
adrenal glands (mineralcorticoids) and kidneys
