S5. Potassium Flashcards
What happens to resting membrane potential when extra cellular K+ rises?
Membrane potential is decreased (depolarised)
What happens to resting membrane potential when extra cellular K+ falls?
Membrane potential increased (hyperpolarised)
Most K+ found where?
Intracellular
Where does reabsorption of K+ occur
First place in PCT (bulk of K+ reabsorbed here). Through solvent drag.
- loop of henle using a NaK co transporter
- DCT through ROMK channels
Where does K+ secretion occur
Late collecting duct SECRETES K+ via ROMK (under influence of aldosterone)
Clinical features of hyperkalemia
- asymptomatic
- possibly muscle weakness or cardiac arrhythmias
- changes on ECG
What can hyperkalaemia result from
Lack of excretion
Release from cells (cell lysis/ acidotic cells)
Excess administration
Too much from diet (only affects UNhealthy kidneys CKD)
Treatment of hyperkalaemia and how it helps?
- calcium gluconate > ca stabilises myocardium
- insulin >drives k into cells. Lower plasma conc of k > less effect on contraction of heart
> given with glucose to avoid hypoglycemia
Whats the only way to remove k+ when don’t have a functioning kidney? (W/o renal replacement therapy)
Calcium resonium >removes k+ by inc excretion from the nowels
Longer term treatment of hypokalaemia
- low k+ dirt
- stop certain medications
- give furosemide > enhances k+ loss in urine
Causes of hypokalaemia
Reduced dietary intake
Inc entry into cells
Inc GI losses
Inc urine loss
Clinical effects of hypokalemia
- muscle weakness, cramps and tetany (intermittent muscle spasms)
- vasoconstriction and cardiac arrythmias
- impaired ADH action causing thirst, polyuria
- metabolic alkalosis due to inc in intracellular H+ conc
Treatment of hypokalaemia
- give potassium replacement
Oral- bananas, oranges
IV- ass KCl to IV bags
Potassium sparing diuretics e.g. spiromoladtone, amiloride
How long will insulin dec K+ for?
6 hours
