Abstract： Background:Postoperative cognitive dysfunction (POCD) is a serious complication after surgery,especially in elderly patients.The anesthesia technique is a potentially modifiable risk factor for POCD.This study assessed the effects of dexmedetomidine,propofol or midazolam sedation on POCD in elderly patients who underwent hip or knee replacement under spinal anesthesia.Methods:The present study was a prospective randomized controlled preliminary trial.From July 2013 and December 2014,a total of 164 patients aged 65 years or older who underwent hip or knee arthroplasty at China-Japan Friendship Hospital and 41 nonsurgical controls were included in this study.Patients were randomized in a 1:1:1 ratio to 3 sedative groups.All the patents received combined spinal-epidural anesthesia (CSEA) with midazolam,dexmedetomidine or propofol sedation.The sedative dose was adjusted to achieve light sedation (bispectral index[BIS] score between 70 and 85).All study participants and controls completed a battery of 5 neuropsychological tests before and 7 days after surgery.One year postoperatively,the patients and controls were interviewed over the telephone using the Montreal cognitive assessment 5-minute protocol.Results:In all,60 of 164 patients (36.6％) were diagnosed with POCD 7 days postoperatively,POCD incidence in propofol group was significantly lower than that in dexmedetomidine and midazolam groups (18.2％ vs.40.0％,51.9％,x2=6.342 and 13.603,P=0.012 and＜ 0.001).When the patients were re-tested 1 year postoperatively,the incidence of POCD was not significantly different among the 3 groups (14.0％,10.6％ vs.14.9％,x2=0.016 and 0.382,P=0.899 and 0.536).Conclusion:Among dexmedetomidine,propofol and midazolam sedation in elderly patients,propofol sedation shows a significant advantage in term of short-term POCD incidence.