Inclusion Criteria:  With American Society of Anesthesiologists (ASA) physical status Ⅱ-Ⅳ Undergo elective non-cardiac and non-neurological surgery receiving general anesthesia Operation time is expected to be longer than 2 hours  Exclusion Criteria:  Clinical diagnosis of dementia Clinical diagnosis of cerebrovascular disorders Clinical diagnosis of heart failure Clinical diagnosis of liver failure Clinical diagnosis of renal failure Clinical diagnosis of traumatic brain injury Alcohol abuse Can not complete the cognitive assessments Refuse to sign informed consent