Eighty ASAI-III elderly patients ( over 65 years ) were randomized equally into 4 groups including a control group without dexmedetomidine and 3 dexmedetomidine groups ( groups D1 , D2 , and D3 ) with loading dexmedetomidine doses of 0.2 , 0.5 , and 0.8 g/kg and maintenance doses of 0.2 , 0.5 , and 0.8 gkg ( -1 ) h ( -1 ) , respectively .