Since the past many years there have been many documented cases of hyponatremia after administration of hypotonic fluids with potential for serious neurological injury in this group of patients.The use of Holliday and Segar's formula to calculate the maintenance fluid regimen in postoperative children leads to an overestimation of the volume of fluid needed, as there is a low urine output in this period. The postoperative period is at risk for non-osmotic secretion of anti-diuretic hormone (ADH), which reduces the ability of kidney to excrete free water and carries risk for development of hyponatraemia.Authors in favour of hypotonic solutions feel that hyponatremia results from excessive volume of fluid and isotonic solutions have risk of hypernatremia, interstitial fluid overload, excessive sodium excretion, and hyperchloremic metabolic acidosis.