Dexmedetomidine is an α-2 adrenoreceptor agonist and has been extensively used through intravenous infusion，in order to improved the quality of block in regional anesthesia. In this prospective, randomized study, the authors focus on the effect of dexmedetomidine mixed with ropivacaine in coracoid approach brachial plexus block.

Inclusion Criteria:

1. American Society of Anesthesiologists (ASA) physical status I or II;
2. Aged 18-60 years;
3. The elbow, forearm, wrist or hand surgery

Exclusion Criteria:

1. History of allergy to local anesthetics;
2. Coagulation dysfunction, neuromuscular disease or local infection;
3. The operation time is longer than the local anesthetics effective time.