ABSTRACT
Sodium is the principal extracellular cation. Normal plasma values are in the range 133145mmol l−1 with a requirement of 1-2mmol kg−1 day−1.
Hyponatraemia
Hyponatraemia is the most common electrolyte abnormality seen in hospitalised patients. It is associated most commonly with increased total body water and sodium, and is compounded by giving hypotonic intravenous (i.v.) fluids.
