Objective To explore the effects of sedationand hemodynamics on different ages patients with the same concentration of dexmedetomidine under general anesthesia. Methods A total of 264 patients( ASAⅠ-Ⅱ) with orthopaedic surgery under general anesthesia in our hospital from April 2013 to May 2015 were divided into 3 groups by age,the young group( group Y,n = 76),middle age group( group M,n = 107),and old age group( group O,n = 81). Fifteen minutes before anesthesia,patients were infused dexmedetomidine with 1...