Dexmedetomidine(Dex)is a specific alpha-2-adrenergic agonist which was widely used in nerve blocks as an adjuvant to local anesthetic(LA) in order to shortening the onset time ,prolonging the analgesic effect and reducing the postop- erative analgesic consumption .When compared with other adjuvant to LA ,Dex was effective in providing better analgesia efficacy with fewer side effects