Objective To evaluate the efficacy of anesthesia with different doses of dexmedetomidine combined with propofol and remifentanil in patients undergoing abdominal surgery.Methods Ninety ASA Ⅰ or Ⅱ patients of both sexes,aged 18-64 yr,weighing 45-80 kg,undergoing abdominal surgery,were randomly assigned into 3 groups ( n =30 each):control group (group C ),dexmedetomidine 0.25 μg· kg-1 · h-1 group ( group D1 ) and dexmedetomidine 0.50 μg· kg-1·h-1 group (group D2 ).Dexmedetomidine was infused at a rate of 0.25 μg·kg-1 ·h-1 and 0.50 μg·kg-1 ·h-1 in groups D1 and D2 respectively until extubation after a loading dose of 0.5 μg/kg over 15 min.In group C,normal saline was infused intravenously at a rate of 10 ml/h.Anesthesia was induced with TCI of propofol with the target plasma concentration (Cp) of 1.0 μg/ml,iv injection of cisatracurium 0.2 mg/kg and TCI of remifentanil with Cp of 3 ng/ml.The patients were tracheal intubated and mechanically ventilated.PETCO2 was maintained 35-40 mm Hg and SpO2 was maintained ≥95％.Anesthesia was maintained with TCI of remifentanil with the target Cp of 5 ng/ml,iv infusion of cisatracurium 0.1 mg· kg-1 · h-1 and TCI of propofol.The target Cp of propofol was increased to maintain Narcotrend index of 37-46.The amount of remifentanil,cisatracurium and propofol consumed,extubation time and eye-opening time,complications during operation and during recovery from anesthesia were recorded.Results There was no significant difference in the amount of remifentanil and cisatracurium consumed and extubation time among the three groups ( P ＞ 0.05).Compared with group C,the eye-opening time was significantly prolonged,the incidence of hypertension and tachycardia during operation,and restlessness,vomitting,hypertension,and tachycardia during recovery from anesthesia was significantly decreased in groups D1 and D2,and the amount of propofol consumed was significantly decreased in group D2 (P ＜ 0.05).Compared with group D1,the eye-opening time was significantly prolonged,the incidence of hypertension during operation,and restlessness,hypertension,and tachycardia during recovery from anesthesia was significantly decreased in group D2 ( P ＜ 0.05).Conclusion When combined with propofol and remifentanil,dexmedetomidine infused at a rate of 0.50 μg·kg-1 · h-1 can provide satisfactory efficacy for abdominal surgery.