Efficacy and Safety of Dexmedetomidine to Bupivacaine in Supraclavicular Brachial Plexus Block

patient will receive Ultrasound -guided Supraclavicular brachial plexus block with 20 ml bupivacaine 0.5% + 1 μg/kg dexmedetomidine.

patient will receive Ultrasound -guided Supraclavicular brachial plexus block with 20 ml bupivacaine 0.5% without additives

patient will receive Ultrasound -guided Supraclavicular brachial plexus block with 30 ml bupivacaine 0.5% without additives as a control group.