Abstract: Objective:To observe the efficacy and safety of dexmedetomidine(Dex) in preventing and treating remifentanil-induced hyperalgesia(RIH).Methods:Eighty patients(stage ASA Ⅰ to Ⅱ) scheduled by radical resection of esophageal carcinoma were randomly divided into the low dose of Dex group(group LD),medium dose of Dex group(group MD),high dose of Dex group(group HD) and control group(group C) (20 cases each group).Before the induction of anaesthesia,group LD,MD and HD were treated with 0.25 μg/kg,0.50 μg/kg and 1.00 μg/kg of Dex by intravenous infusion for 10 min,then with 0.25 μg·kg^-1·h^-1,0.50 μg·kg^-1·h^-1 and 1.0 μg·kg^-1·h^-1 of Dex till 30 min before the end of the operation,respectively.The C group were treated with the same volume 0.9% sodium chloride injection.The score of improved OAA/S after extubation,and the scores of VAS 10 min,30 min,1 h,2 h,6 h,12 h and 24 h after extubation in four groups were recorded.The total drug mount in PCA and incidence rate of postoperative adverse reactions in four groups 24 h after operation were recorded.Results:The scores of VAS in group LD,MD and HD after extubation were significantly lower than that in group C(P<0.01),which was dose-dependent.The total drug mount in PCA and incidence rates of postoperative adverse reactions in group LD,MD and HD after 24 h of operation were significantly less than those in group C(P<0.01).Conclusions:Intraoperative infusion of medium dose of Dex can safely and effectively relieve postoperative pain,attenuate high-dose remifentanil-induced hyperalgesia,reduce the complication and improve the satisfaction of patients.