Potassium and Hydrogen Homeostasis Flashcards
Normal Potassium
3.6 - 5.0 mmol/L
Values 6 dangerous causing
Cardiac conduction defects and abnormal neuromuscular excitability
Measurement
Serum K conc, don’t reflect body, as 98% in cells, total body K+ determined by total cell mass, always exchange ICF-ECF influenced by acidosis, insulin/glucose therapy, adrenaline, rapid cellular incorporation (TPN, leukaemia)
How much potassium intake all day?
60-200 mmols/day
Hydrogen and Potassium
Exchange across cell membrane, both bind to negatively charged proteins, changes in pH causes shift in equilibrium
Acidosis causes
K+ move out of cells (hyperkalaemia)
Alkalosis causes
K+ move into cells (hypokalaemia)
Causes of hyperkalamia
Delay in sample analysis (may leak), haemolysis (small needles taking blood sample, shear force break them up), drug therapy (excess intake), acute/chronic renal failure, acidosis (intracellular exchange), adrenocortical failure (protects against), mineralocorticoid resistance (spironolactone), cell death
Treatment of hyperkalaemia
Correct acidosis, stop unnecessary supplements, give glucose and insulin (drives potassium into cells), ion exchange resists (GIT K binding), dialysis
Causes of hypokalaemia
Low intake, increased urine loss (diuretics/osmotic diuresis, tubular dysfunction, mineralocorticoid excess), GIT losses (vomitting, diarrhoea/laxitatives, fistulae), without depletion (alkalosis, insulin/glucose therapy)
Acute effects of hypokalaemia
Neuromuscular - lethargy, muscle weakness, heart arrhythmias
Chronic effects of hypokalaemia
Lethargy, muscle weakness, heart arrhythmias, polyuria, alkalosis increased renal HCO3 production
Treatment of hypokalaemia
Prevention (supplements), replacement (oral - no more than 48mmol day) and (IV
