Traditionally, maintenance fluid replacement in children about 50 years ago based on Holliday Segar liquid formula Hypotonic used. In recent years, studies have shown that the use of Hypothonic liquid can Hyponatremia some children due to fluid therapy. In some cases, Hyponatremia can lead to irreversible neurological symptoms and even death. Hypothonic ( serum containing 30 meq/lit in children under 12 months, containing 50 meq/lit children over 12 months ) with intravenous fluid contains high levels of sodium ( serum containing 50 meq/lit in children under 12 months and children over 12 months liquid 100meq.lit ), on admission and 24 hours after starting rehydration, compared to volume urine in children receiving intravenous fluid Hypothonic with intravenous fluid contains high levels of sodium, on admission and 24 hours after starting rehydration compared blood pressure changes in children receiving intravenous fluid Hypothonic with intravenous fluid contains high levels of sodium, on admission and 24 hours after starting rehydration compared the prevalence of hypernatremia , Hyponatremia (serum sodium level greater than 135 - 145 ) in both fluids. Inclusion criteria: children in age from 30 days to 14 years without speaking to him prescribe intravenous fluid for at least 24 hours in the ICU Bahrami Children Hospital, Tehran University of Medical users are admitted. Exclusion criteria: patients with acute or chronic renal parenchymal; patients at risk of cerebral edema; diabetic ketoacidosis; head trauma; heart disease; patients Hypoglycemia; patients with abnormal secretion of antidiuretic hormone; diabetes insipidus disorders; pituitary or hypothalamic; patients underwent surgery to have lost a lot of blood during surgery; patients after surgery of cranial or thorax; cirrhotic patients; patients with severe malnutrition; diabetes; any disease that his doctors do not accept this fluid. Withdrawal criteria: children with higher serum sodium lower than the normal range (135_145); would be required CPR; intubation; death, early oral feeding, any conditions that the patient's physician his decision to withdraw from the study or decide to change intravenous fluids. In the beginning especially sodium levels, blood pressure and urine specific gravity will be check and again 24 hours after initiation of intravenous fluid to be re- check. Liquid sodium 50 and 100 mEq per liter of liquid will be used. Fluid besides sodium respectively containing potassium of 20 mEq per liter of liquid glucose to a concentration of 10 grams per liter. Fluid volume shall be calculated according to the formula Holliday _ segar , so go for one weighing 10 kg and 10 kg weight Kg 100 cc per second per Kg weight of 50 cc and 20 cc per kg body weight remaining Kg weight may be given intravenous fluid every 24 hours . Finally, the groups are compared in terms of average plasma sodium. The specific gravity of the urine and blood pressure before and after receiving IV therapy is evaluated.