People who have shoulder surgery are given medicine so they do not feel pain during the procedure. This includes a nerve block that makes the shoulder numb, along with medicine that keeps the person asleep. The nerve block usually keeps the shoulder numb for about three to five days. Pain after surgery often lasts longer than this. In this study, doctors are testing whether adding another medicine called dexamethasone can make the numbness last longer. If you join the study, you will be placed into one of two groups. One group will get the usual nerve block, and the other group will get the nerve block with the extra medicine. In both groups, you will be asleep during surgery. The only difference is how long the numbness in the shoulder may last.