Abstract: Objective To assess the effect of dexmedetomidine on agitation in awakening period of liver cancer patients after high intensity focused ultrasound(HIFU) therapy. Methods One hundred 48-80 years old ASA Ⅱ or Ⅲ liver cancer patients with their BMI being 18.2-26.5 kg/m²,admitted to General Hospital of Second Artillery Forces for HIFU therapy from December 2009 to January 2013,were randomly divided into control group and dexmedetomidine treatment group(50 in each group).Patients in dexmedetomidine treatment group were intravenously infused at the dose of 0.7μg/kg for 15 min before anesthesia followed by 0.2 μg/(kg·h) till the end of operation and those in control group were infused with the equal volume of 0.9% sodium chloride solution.Patients in both groups were anesthetized through iv injection of fentanyl(2-3 μg/kg),propofol(1.5-2 mg/kg)and cisatracurium(0.2 mg/kg) 5 min after the loading dose was infused and maintained by inhaling sevoflurane(the end-tidal concentration was 1.5%-2%) and pumping remifentanil 0.01-0.02 mg/(kg·h) and propofol 1.5-2 mg/(kg·h) into trachea,and adding cisatracurium(0.05 mg/kg) when needed with the BIS maintained at 40-60.The volume of propofol,remifentanil and sevoflurane used,and the incidence of agitation in wakening period and delirium within 24 h after operation were recorded. Results The volume of propofol,remifentanil and sevoflurane used,the incidence of agitation in awakening period and delirium within 24 h after operation,and the heart rate were significantly lower in dexmedetomidine treatment group than in control group(P<0.05). Conclusion Dexmedetomidine can effectively reduce the incidence of agitation in awakening period of liver cancer patients after HIFU therapy and the volume of narcotics.