Effect of Tolvaptan in preventing decrease in blood sodium levels after surgery

INTERVENTION: Intervention1: Tolvaptan: Oral tolvaptan 15mg one hour before surgery Control Intervention1: Placebo: Similar looking placebo tablet orally one hour before surgery CONDITION: Health Condition 1: K402‐ Bilateral inguinal hernia, withoutobstruction or gangrene Health Condition 2: K800‐ Calculus of gallbladder with acutecholecystitis Health Condition 3: N201‐ Calculus of ureter Health Condition 4: H701‐ Chronic mastoiditis Health Condition 5: C501‐ Malignant neoplasm of central portion of breast Health Condition 6: M171‐ Unilateral primary osteoarthritisof knee PRIMARY OUTCOME: Serum sodium valuesTimepoint: On first postoperative day SECONDARY OUTCOME: Urine output ; Blood pressure ; Postoperative stayTimepoint: During surgery ; Postoperative period INCLUSION CRITERIA: All adult patients undergoing major surgeries of more than 2 hours duration under regional or general anaesthesia