Hyponatremia Study (Delayed Hyponatremia After Pituitary Surgery)

"Patients will be started on a weight-based intravenous fluid replacement with D5 ½ NS on POD 0 (75 cc/hr for patients \< 70kg, 100 cc/hr for patients 70-100kg, and 125 cc/hr for patients \>100kg). Patients will be allowed to drink water freely after surgery on POD #0. Fluids will be stopped at 8am on POD 1 and patients will be started on a moderate fluid restriction on POD #3 based on their weight (1000 cc/24 hours for patients who weigh \<=100 kg and 1200 cc/24 hours for patients who weigh \> 100kg). Prior to initiation of a fluid restriction all of the following criteria have to be met:~1. Serum Na level must be \< 145 mEq/l~2. Patient should be taking fluids by mouth~3. Patient should not have evidence of DI (as determined by endocrine team following patient) If a patient in Fluid Restricted group develops DI, the fluid restriction will be stopped/not initiated."