Abstract: Objective:To investigate the effects of different concentrations of dexmedetomidine(DEX) on early cognitive function and inflammatory parameters in elderly patients treated with orthopedic surgery.Methods:Ninety elderly patients treated with general anesthesia operation,aged 60 to 85 years,ASA Ⅰ~Ⅲ and without severe liver and kidney disease and active inflammation,were divided into the 0.5 μg/kg DEX group(groupD1),1.0 μg/kg DEX group(group D2) and control group(group C) (30 cases each group).The preoperative and postoperative cognitive function in three groups were evaluated using Mini Mental State Examination(MMSE).The inflammatory parametersincluding serum interleukin -1β(IL-1β),serum interleukin -6(IL-6),tumor necrosis factor -α(TNF-α) and high-sensitivity C-reactive protein(hs-CRP) and oxidative stress parametersincluding serum super-oxide anion(O₂^-),hydroxy radical(OH),malondialdehyde(MDA) and super-oxide dismutase(SOD) between three groups before 5 min of anesthesia(T₀),after 30 min of begining operation(T₁),at the end of operation(T₂),postoperative 2 h(T₃),postoperative 1 d(T₄) and postoperative 3 d(T₅) were compared.Results:The differences of inflammatory parameters between three groups before operation were not statistically significant(P>0.05).Compared with before operation,all parameters in group C gradually increased after 3 d of operation.The serum levels of IL-1β in group D1 at T₂ and T₃ increased,but which was lower than that group C.The serum levels of IL-6,TNF-αand hs-CRP in group D1 gradually increased from T₁ to T5,but which was lower than that in group C.There was not significant change of the levels of IL-1β in group D2 at each time-point,and the levels of IL-6,TNF-α and hs-CRP in group D2 at T₂,T₃,from T₁ to T₃ and from T₁ to T₅ gradually increased with compared before operation.The differences of the oxidative stress parameters between three groups with before operation were not statistically significant.Compared with before operation,the levels of O₂^- and MDA in group D1 and D2 gradually increased from T₂ to T5,and which in group D2 was lower than that in group D1 and C.Compared with before operation,the level of SOD gradually decreased,and the level of SOD in group D2 was higher than that in group D1 and C.Compared with before operation,the level of OH in group D1 and D2 gradually increased,which in group D2 and D1 from T₁ to T₅ were lower that in group C.Conclusions:DEX can reduce the early cognitive dyfunction in elderly patients treated with orthopedic surgery by inhibiting oxidative stress and inflammation reaction.