Last updated: Tuesday, 14, December, 2010
Hyponatraemia may occur with dilution of plasma sodium (total body sodium may be normal or increased) or withdehydration and excess sodium loss.
Excessive sodium loss may be renal or extra-renal and the effect may be exacerbated by replacement with oral or IV fluids containing little or no sodium.
Electrolytes, urea, creatinine; sodium - urine.
See Table 1.
Osmolality; urine - osmolality, sodium.
Dilutional / Water (fluid) overload
Renal sodium loss
Salt-wasting renal disease
Creatinine, urea; urine - sodium, potassium, osmolality.
Extra-renal losses and/or sequestration
Operative blood/fluid loss