3. Post operative delirium and postoperative cognitive dysfunction diagnosis: Patients completed neuropsychological tests at entry to the study-generally the day before surgery-and at discharge from hospital or 1 week. The investigators assessed delirium by the Confusion Assessment Method for the intense care unit. The neuropsychological tests include Wechsler Adult Intelligence Scale-Revised by China Visual Reproduction、Wechsler Adult Intelligence Scale-Revised by China Digit Span、Digit-Symbol Substitution Test、The Stroop Color-Word Test、Trail Making Test A and Trail Making Test B. Patients had cognitive dysfunction when two Z scores in individual tests or the combined Z score were 1.96 or more.