A total of 120 patients , aged between 20 to 50 years old , who were scheduled to receive elective gynecological open surgery under general anesthesia , were randomly divided into 3 groups : the control group , furosemide 0.05 mg/kg ( F0 .5 ) group and furosemide 0.1 mg/kg ( F1 ) group ( n = 40 ) .