Objective To evaluate the effect of dexmedetomidine on lung injury induced by extremity ischemia-reperfusion.Methods Forty patients,aged 18-60 yr,with body mass index of 20-25 kg/m2,of ASA physical status Ⅰ or Ⅱ,with 1 h ≤ predicted duration of surgery ≤ 1.5 h,were randomly divided into 2 groups (n =20 each) using a random number table:control group (group C) and dexmedetomidine group (group D).In groupD,dexmedetomidine 1 (g/kg was infused intravenously for 10 min,followed by continuous infusion of dexmedetomidine at 0.5 μg· kg-1 · h-1 until the end of the surgery,while in group C the equal volume of normal saline was given instead.Immediately before induction of anesthesia (T1,baseline),at 60 min after tourniquet was inflated (T2) and at 30 min,2 h and 6 h after tourniquet release (T3-5),blood samples were collected from the radial artery for blood gas analysis and for measurement of the levels of plasma interleukin-6 (IL-6),IL-8,tumor necrosis factor-α (TNF-α),malondialdehyde (MDA) and superoxide dismutase (SOD),and arterial partial pressure of oxygen (PaO2) and partial pressure of carbon dioxide (PaCO2) were recorded.Alveolar-arterial oxygen difference (A-aDO2) and respiratory index (RI) were calculated.Results Compared with group C,PaO2 was significantly increased at T5,and A-aDO2 and RI at T5,the levels of plasma IL-6 and IL-8 were decreased at T4,5 and the levels of plasma TNF-α,MDA and SOD were decreased at T3-5 in group D.Conclusion Dexmedetomidine can attenuate lung injury induced by extremity ischemia/reperfusion via inhibiting inflammatory responses and lipid peroxidation.