Intravenous Dexamethasone on Supraclavicular Brachial Plexus Block for Shoulder Arthroscopy

Numerous studies have confirmed that perineural dexamethasone prolongs bupivacaine and ropivacaine brachial plexus blocks by approximately 10 hours (from approx. 12 to 22 hours) without clinical evidence of toxicity. However, perineural toxicity in an animal model has raised concern about its use as a peripheral nerve block adjuvant. Moreover, recent studies suggest that high dose IV dexamethasone (810mg) prolongs analgesia to a similar degree as perineural dexamethasone for interscalene, supraclavicular and sciatic nerve blocks performed with ropivacaine and bupivacaine. However these studies only utilized fixed, high level doses of IV dexamethasone. Moreover, there remains a concern that high dose IV dexamethasone may lead to postoperative hyperglycemia and could possibly increase the risk of postoperative wound infection. Open surgery under general anesthesia has been shown to increase blood glucose levels with a peak at approximately 2 hours post-induction and results have been conflicting regarding whether or not IV dexamethasone causes greater increase. To the investigators' knowledge, it is not yet known if arthroscopic surgery under regional anesthesia triggers a similar increase in blood glucose levels and if this is impacted by administration of IV dexamethasone. The investigators aim to identify the duration of supraclavicular block prolongation that can be expected over a range of doses of IV dexamethasone. The investigators also seek to identify what association, if any, is noted between IV dexamethasone and changes in blood glucose levels after shoulder surgery with regional anesthesia and sedation. Finally, the investigators will collect data on side effects and postoperative complications, if any, in patients receiving a range of doses of IV dexamethasone.