Preoperative Pain and POCD in Elderly Patients

Inclusion Criteria: 1. Elder than 65 years old 2. Speak Chinese Mandarin 3. Those who will undergo major low limb surgery like hemiarthroplasty or total hip arthroplasty with general anesthesia. 4. Signed the inform consent 5. American Society of Anesthesiologists classification I to II Exclusion Criteria: 1. Existing cerebral disease, or have a history of neurological and psychiatric disease including Alzheimer Disease, stroke, epilepsy and psychosis 2. Existing cognitive impairment as evidenced by Mini-Mental State Examination scores below 24 3. Severe hearing or visual impairment 4. Unwillingness to comply with the protocol or procedures 5. Cannot communicate with Chinese Mandarin 6. Serious pulmonary, heart , liver or renal insufficiency patients 7. Had anesthesia or surgery within the past 30 days