Pharmacology: Hyperkalemia, Hypokalemia Flashcards
describe the ECG changes with hypokalemia
- flattened T waves
- ST segment depression
- prolonged QT interval
- U waves
- atrial arrhythmias
- v tach, v fib
describe the ECG changes with hyperkalemia
- tall T waves
- prolonged PR interval
- widened QRS interval
- flattened P waves
- arrhythmias – bradycardia, v tach, v fib
- sinus arrest or nodal rhythm w/ possible asystole
name the K-sparing diuretics
- triamterene, amiloride (Na channel blockers)
2. spironolactone (aldosterone agonist)
name the K-wasting diuretics
- thiazides (NaCl cotransporter blockers)
- loop diuretics (NaK2Cl cotransporter blockers)
- carbonic anhydrase inhibitors (rarely used)
- osmotic diuretics (non-reabsorbable solutes)
name the site of action:
carbonic anhydrase inhibitors
PCT
name the site of action:
osmotic diuretics
PCT, thin descending limb
name the site of action:
loop diuretics
TAL
name the site of action:
thiazide diuretics
DCT
name the site of action:
Na-channel blockers
cortical CD
name the site of action:
vaptans
CD
furosemide MOA
- directly inhibits reabsorption of Na and Cl in TAL via blocking NaK2Cl cotransporter (loop diuretic; K-wasting)
- indirectly inhibits paracellular reabsorption of Ca and Mg by TAL d/t loss of K backleak responsible for lumen + transepithelial potential
furosemide effects
increased excretion: Na, H2O, K, Cl, Mg, Ca
furosemide applications
- edema from CHF, hepatic disease, renal disease
- acute pulmonary edema (decrease preload; rapid dyspnea relief)
- HTN (alone or combo; will work in pts w/ low GFR*)
furosemide pharmacokinetics
- onset: IV ~5 mins, PO and IM 30 mins
- duration: 6-8 hrs oral, 2 hrs IV
- half life: ~0.5-2 hrs, longer if low GFR
- eliminated unchanged in urine
furosemide toxicities
- hypo: K, Na, Ca, Mg
- hypochloremic metabolic alkalosis
- ototoxicity
- sulfonamide, risk of HSN
- hyperglycemia; hyperuricemia; hyperlipidemia
sulfonamide similar to furosemide w/ longer t1/2, better oral absorption and evidence of higher effectiveness in HF
torsemide
sulfonamide similar to furosemide w/ more predictable oral absorption
bumetanide
non-sulfonamide loop diuretic
ethacrynic acid
*reserved for those w/ sulfa allergy