40 patients (ASA Grade 1 to 2) scheduled to undergo hand and forearm surgery with tourniquet and brachial plexus anesthesia via axillary approach for upper-limb block were randomized to receive a continuous infusion of dexmedetomidine or saline as placebo until the end of surgery. Following evaluations over a 2 week period, results exhibited that the dexmedetomidine treatment led to a significant decrease the plasma hypoxanthine production in ischemic period and plasma malondialdehyde production in the reperfusion periods. The dexmedetomidine group had significantly lower blood creatine phosphokinase and uric acid levels after reperfusion compared to the control group.