This study is designed to test the hypothesis that closed loop system reduces post operative cognitive dysfunction incidence 15 min after anesthesia more than desflurane, sevorane, total intravenous anesthesia manually guided by bispectral index in urologic surgical patients.

The secondary aim is to evaluate the postoperative cognitive impairment in in elderly vs younger surgical patients.

Postoperative cognitive dysfunction (POCD) is a transient cognitive impairment manifested by compromised memory and concentration with altered performance on intellectual tasks that can affect patients of any age but it is more frequent in advanced age people after anesthesia.

Recently clinical research has demonstrated the efficacy of computer- controlled endovenous drug delivery system guided by bispectral index score (BIS) of the electroencephalogram as the control variable. The BIS closed loop (CL) titration of propofol and remifentanyl target control infusion provides clinically adequate anesthesia with stability of cardiovascular parameters and favorable patients outcomes, including decreasing drug consumption and shortened postoperative recovery times when compared with manual control infusion.

Inclusion Criteria:

• Patients aged above 18 years
• Patients undergoing elective urologic surgery under general anesthesia expected 2 hours
• American Society of Anesthesiology physical status II- III

Exclusion Criteria:

• Patients with body mass index greater than 30,
• Patients with clinically significant cardiopulmonary, hepatic, renal disorders, neurological, psychiatric or metabolic disease
• Patients unable to read and write and with impaired hearing