In the study of Gandhi R and et al. (2012), the onset of sensory and motor blockage in combined dexemedetomidine group was faster than alone local anesthetic group, duration of sensory and motor blockage were 732 minutes and 660 minutes, shoter than about 100 minutes of our BD group, is 825 and 800 minutes, explaining this difference may be due to two different assisted technique in practiced anesthesia, we did ultrasound guidance while Gandhi R used anatomical technique to do brachial plexus block.