Changes in extracellular Na+ concentration result in increase or decreases in the osmolality of the ECF, which in turn, influence the distribution of body water. It is therefore related in regulation of water balance as well as blood volume in the body.
Normally, serum Na+ concentration varies between 136 and 145 mmol/L in healthy individuals. The normal daily intake of Na+ is 100-250 mmol. Ordinarily, the amount of Na+ loss is balance by the daily intake.
A decrease in serum sodium level, termed as “hyponatremia” is usually seen in hypoadrenalism, potassium deficiency, diuretic use, ketonuria, salt-losing nephropathy, prolonged vomiting, diarrhea, renal failure, hepatic cirrhosis, congestion heart failure (CHF) and diabetic ketoacidosis.
Whereas, an increase in serum sodium level, termed as “hypernatremia” is seen in profuse sweating, severe burns, dehydration, malnutririon, edema, ascitis in chronic failure, uncontrolled diabetes, and nephritic syndrome.