The purpose of this study is to determine whether postoperative analgesia pump continuous infusion of dexmedetomidine are effective in the prevention of Postoperative delirium and Postoperative cognitive dysfunction.

1. collection of cases: This trail is approved by Hospital Ethics Committee, and patients who participated in the study signed the informed consent. The subject will select 300 elder patients (age ≥60 years) routine tumor surgery, American Society of Anesthesiologists classificationⅠ-Ⅲ. Preoperative liver and kidney function, blood electrolytes were in the normal range.
2. Case group: Selected cases divided into the right dexmedetomidine group and control group by computer randomly, 150 patients in each group. Dexmedetomidine group (A group) analgesia pump formula is: 3 ug/kg sufentanil and 3 ug/kg dexmedetomi-dine, with 0.9% saline diluted to 150ml. Control group (group C) postoperative analgesia formula is: 3 ug/kg sufentanil, with 0.9% saline diluted to 150ml. Two group with the same anesthesia program.
3. Our primary outcome was the 7-day incidence of postoperative delirium assessed by CAM-ICU twice daily (8 a.m. and 8 p.m.) and supplemented with a review of medical and nursing records. The assessment was carried out by investigators who had been trained prior to the trial and were unaware of the group assignment.All investigators and patients were unknown of experiments and results. The four clinical criteria for CAM-ICU are as follows: (1) acute onset with fluctuating course of disease; (2) inattention; (3) altered level of consciousness; (4) disorganized thinking. Delirium can be diagnosed by the appearance of both features 1 and 2, with at least one of features 3 or 4. RASS was used to measure sedation or agita-tion prior to testing delirium. If the patient was deeply sedated or unable to fall asleep (RASS - 4 or - 5), delirium assessment was halted; if RASS score was of - 3 or above, delirium was evaluated by CAM-ICU.

Inclusion Criteria:

• Patients' age ≥60 years
• Underwent elective non-cardiac surgery under general anesthesia

Exclusion Criteria:

• Patients with severe bradycardia (heart rate<55bpm)
• Severe arrhythmia or cardiac dysfunction (ejection fraction<35%)
• Mini-Mental Scale Test (MMSE) Exclusion criteria: illiteracy <18, primary school <21, junior school and above <25
• Preoperative clear systems and spiritual history of neurological disease or long-term use of sedatives or antidepressants
• History of alcohol abuse or a history of drug dependence
• Have brain surgery or trauma
• Severe vision or hearing impairment
• Cannot with the completion of tests of cognitive function
• Refused to participate in the study