Dexmedetomidine, was reported to prevent postoperative delirium in elderly patients following its use in intensive care units. Possible mechanisms included improved quality of sleep and an inhibitory effect on inflammation. A greater number of studies indicated that propofol has negative effect on postoperative cognitive function. In this study, we planned to investigate the influence of these two different sedative drugs on peripheral inflammation induced by surgery and postoperative cognitive function of patients who will receive hip and knee arthroplasty.

Dexmedetomidine, was reported to prevent postoperative delirium in elderly patients following its use in intensive care units. Possible mechanisms included improved quality of sleep and an inhibitory effect on inflammation. A greater number of studies indicated that propofol has negative effect on postoperative cognitive function. In this study, patients who will receive hip and knee arthroplasty will be divided to two groups: Propofol group and Dexmedetomidine group. Spinal anesthesia will be used to meet the requirement of intraoperative analgesia. Patients in two groups will be sedated by propofol and dexmedetomidine, respectively. TNF-α and IL-6 in blood will be detected. And postoperative cognitive function of patients will be investigated. The objective of this study is to clarify the influence of these two different sedative drugs on peripheral inflammation induced by surgery, and the relationship with the change of postoperative cognitive function.

Inclusion Criteria:

• The patients included in this study were 65 years or older, were undergoing total hip arthroplasty, and were classified as American Society of Anesthesiologists (ASA) physical health class I-IV.

Exclusion Criteria:

• Contraindications to spinal anesthesia (i.e., coagulopathy, concurrent use of anticoagulants, infection at puncture site, and refusal of spinal anesthesia), patients with infectious diseases, patients with mental or language barriers, patients who had been anesthetized within the past 30 days, severe congestive heart failure (New York Heart Association, class IV) and/or severe chronic obstructive pulmonary disease (Global Initiative for Chronic Obstructive Lung Disease Guidelines, stages III-IV), sick sinus syndrome, severe sinus bradycardia (< 50 beats per min), and second or greater atrioventricular block without pacemaker. In addition, patients exhibiting cognitive impairment (i.e., a Mini-Mental State Examination (MMSE) score < 24) and/or preoperative delirium (i.e., positive Confusion Assessment Method (CAM) result) were excluded.

We don't want to open individual participant data (IPD) available to other researchers.

Outcomes Assessor will be blinded to this study.