Effectiveness of Ultrasound (US) Guided Supraclavicular Block

This research study is being done in order to find out if there is any difference in the effectiveness of ultrasound guided supraclavicular brachial plexus nerve block that can be achieved with 3 different amounts of ropivacaine 0.5% (20 ml, 30 ml, and 40 ml). The investigators want to show if you can have a successful nerve block with less amount of local anesthetic, thus potentially decreasing the risk of side effects.