Objective:To evaluate the effect of dexmedetomidine mixed with dexamethasone on efficacy of ropivacaine for popliteal sciatic nerve block in the patients undergoing ankle surgery.Methods:A total of 120 patients of either sex, aged 30-64 yr, with body mass index of 19.6-29.7 kg/m 2, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, undergoing elective ankle surgery, were divided into 4 groups ( n=30 each) by a random number table method: control group (group C), dexmedetomidine group (group DD), dexamethasone group (group DM), and dexmedetomidine plus dexamethasone group (group DD+ DM). In group C, 0.5% ropivacaine 30 ml was injected around the popliteal sciatic nerve guided by ultrasound combined with a nerve stimulator.Dexmedetomidine 1 μg/kg, dexamethasone 10 mg and dexmedetomidine 1 μg/kg plus dexamethasone 10 mg were added to 0.5% ropivacaine in group DD, group DM and group DD+ DM, respectively.The analgesic time, consumption of sufentanil and adverse reactions were recorded after popliteal sciatic nerve block. Results:Compared with group C, the analgesic time was significantly prolonged, the consumption of sufentanil was reduced, and the incidence of nausea and vomiting was decreased in group DD, group DM and group DD+ DM ( P<0.05). Compared with group DD and group DM, the analgesic time was significantly prolonged, and the consumption of sufentanil was reduced in group DD+ DM ( P<0.05). No itching, drowsiness, hypotension, bradycardia or respiratory depression occurred in each group. Conclusion:Dexmedetomidine mixed with dexamethasone can effectively enhance the efficacy of ropivacaine for popliteal sciatic nerve block in the patients undergoing ankle surgery.