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REGUB Path - Disorders of Potassium Balance (ii) Hypokalaemia…
REGUB Path - Disorders of Potassium Balance (ii) Hypokalaemia
Intro
K serum level < 3.5 mmol/L
NOT total body levels (can't measure intracellular, where most of it is)
moderate if < 3
severe if < 2.5
compensation: if serum level low, K is brought out of cells to try maintain normal serum levels
3 sources
decreased intake
rarely the sole aetiology, as urinary K losses can go as low as 10mmol/day
causes more total body depletion than hypokalaemia
more often a contributing factor in other primaries aetiologies of hypokal
can be caused by lots of vomiting (e.g. bulimia nervosa)
intracellular shift
cell growth
periodic paralysis
tocolytics for preterm labour (anti-contraction medications, labour suppressants)
B-agonists for asthma + COPD (remember catechols drive K+ intracellularly)
refeeding syndrome: sudden production of insulin - big intracellular K shift
increased renal excretion
secondary hyperaldosteronism (caused my massive ascites, left HF + cor pulmonale)
diuretics
loop + esp thiazides increase Na delivery to distal tubule - stims aldosterone sensitive ENaC
vomiting - lots of bicarb excreted due to lost stomach acid
salt wasting nephropathies
primary hyperaldosteronism aka Conn's syndrome (due to adenoma) - causes HTN
K wasting nephropathies
hypomagnesia
drug toxicity
unresorbable anions
RTA
polyuria
Consequences
muscle weakness/paralysis
ECG changes + arrhythmia
urinary concentrating deficits
HTN + stroke
Tx
oral K preferred over IV
IV can cause phlebitis (toxic to veins), vol overload (if K in saline), release of insulin (if K in dextrose)