Session 5- Regulation of Potassium Flashcards
normal range of potassium
3.5 - 5.5 mmol/l
how does membrane potential change with ECF K+
if ECF K+ rises the resting membrane potential is decreased
if ECF K+ falls the resting membrane postential is increased
hypokalaemia on a ECG
slightly prolonged PR interval
slighly peaked P wave
shallow T wave
prominent U wave
ST depression
hyperkalaemia on ECG
decreased R wave amplitude
wide, flat P wave
prolonged PR interval
widened QRS
decreased ST segement
Tall peaked T wave
water distribution in body
60% is water
of that 2/3 intra 1/3 extra
of 1/3 extra 25% plasma 75% interstitual fluid
where is the majority of K reabsorbed
67% PCT
Thick ascending limb through NKCC
DCT- ROMK
where is k reabsorbed and secreted
collecting duct -ROMK
how does teh kidney alter the secretion of K in alkalosis
Beta intercalated cells in PCT
reabsorbs H+
secrete K+ and HCO3-
How does the kidney alter the absorbption of K+ in acidosis
Alpha intercalated cells in PCT
secrete H+
reabsorb K+ and HCO3-
Clinical features of hyperkalaemia
muscle weakness
cardiac arrythmias
what can cause hyperkalemia
lack of excretion
release from cells
excess administration
how do we treat hyperkalaemia
calcium gluconate - Ca2+ stabalises the myocardium preventing arrythmias
insulin-drives K+ into cells to lower plasma conc. Given with glucose to avoid hypoglycaemia
calcium resonium- removes K+ by increasing excretion from the bowels
what causes hypokalaemia
reduced dietary intake
increased entry into cells
increase GI losses
increased urine loss
clinical effects of hypokalaemia
muscle wekaness, cramps and tetany
vasoconstriction and cardiac arrythmias
impaired ADH action causing thirst, polyuria and no conc of urine
metabolic alkalosis due to increas ein intracellualr H+ conc
how do we treat hypokalaemia
potassium replacement
- oral
- iv
- potassium sparing diuretics
