 OBJECTIVES AND HYPOTHESES In this factorial design study of outpatients undergoing elective arthroscopic shoulder surgery with interscalene brachial plexus block ISB, the investigators will compare perineural and intravenous administration of dexamethasone at high 8mg and low 4mg doses. The investigators hypothesize that high doses and the perineural route will provide significantly longer duration of analgesia, without significant statistical interaction between dose and route of administration. 