K+ Flashcards
what is the normal plasma [K+]?
3.5-5 mEq/L
What hormones regualte K and what do they do?
Insulin and epinephrine (beta-2 stimulation), active Na/K ATPase
what are some causes of hyperkalemia?
beta-blockers (inhibits ATPase), digoxin, intense exercise, acidosis
ekg changes in hyper and hypokalemia
tall t, v fib, wide complex; flat t, high u
How is K excretion controlled?
changes in secretion (not much reabsorption change)
where is K reabsorbed?
65% PT, 25% TAL, CT varies
what is the driving force for K secretion across apical membrane and what does this mean?
chemical gradient (affected by urine flow rate) and electrical gradient (activity of ENaC)
what are the two key determinants of CCD secretion of K
aldosterone and Na delivery and transport
what are some blockers of Na channels?
Amiloride, triamterene, trimethoprim (bactrim), pentamidine
what are some causes of kidney hyperkalemia
decreased GFR, aldosterone deficiency, decreased Na delivery or blockage of Na channels. Also, NSAIDS and ACEI
what is the main stimulator for aldosterone?
AT2,K+. So ACEI can cause hyperkalemia
causes of aldosterone deficiency
low plasma renin
Depletional vs nondepletional hypokalemia
depletional- gi (vomiting, diarrhea), renal (aldosterone excess, diuretics, Bartter and Gitleman, RTA), low intake. nondep- redistribution (albuterol, ^ insulin)
primary vs secondary hyperaldosteronism
cause hypokalemia w/htn. Primary (tumor) has decreased renin, secondary has increased renin
bartters syndrome
NKCC2 mutation (K/Cl/Na channel)
