Toronto Notes Nephrology 2015 8
Toronto Notes Nephrology 2015 8
Toronto Notes Nephrology 2015 8
Electrolyte Disorders
Hyponatremia
Hypo-Osmolar (dilutional)
Most common cause of
hyponatremia
Excess water in relation to
sodium stores which can be
decreased, normal, or increased
Categorized by volume status
as determined by clinical
assessment
Hypervolemic
UNa<20 and FeNa >1% (renal losses)
CHF
Cirrhosis and ascites
Nephrotic syndrome
Pregnancy
UNa>20
AKI, CKD
Iso-Osmolar
Retention in ECF of large volumes
of isotonic fluids that do not
contain sodium (e.g. mannitol)
Pseudohyponatremia lab artifact
seen with severe hyperlipidemia
or paraproteinemia (e.g. multiple
myeloma)
Euvolemic
Uosm>100
SIADH (normal UNa)
Adrenal insufficiency
Hypothyroidism
Uosm<100
Psychogenic polydipsia
Low solute - tea & toast
Hyper-Osmolar (translocational)
Extra osmoles in ECF draw
water out of cells diluting the
Na+ in ECF
Usually glucose (rarely
hypertonic mannitol)
Every 10 mmol/L increase in
blood glucose results in
3 mmol/L decrease in Na
Hypovolemic
UNa>20
Diuretics (especially thiazides)
Salt-wasting nephropathy
UNa<10 and FeNa<1% (extra-renal losses)
Diarrhea
Excessive sweating
Third spacing (e.g. peritonitis,
pancreatitis, burns)