Ropivacaine Block Alone or With Perineural or Systemic Dexamethasone for Pain in Shoulder Surgery

Pre-operative perineural injection of dexamethasone mixed with local anesthetic in peripheral nerve blockade for orthopedic surgery has been shown to prolong the length of analgesia, improve visual analog pain scores, decrease post-operative opioid use, and decrease post-operative nausea. No study has been published to determine if this effect is a result of systemic absorption of dexamethasone or is a local effect of the drug on neuronal activity at the injection site. This study is a prospective, randomized, double-blind, controlled study to compare pain block with (1) ropivacaine and saline plus intravenous saline vs (2) ropivacaine and dexamethasone plus intravenous saline vs (3) ropivacaine and saline plus intravenous dexamethasone. Patients will be recruited sequentially and assigned to the three groups at random in equal ratios. The hypothesis is that dexamethasone injected perineurally in combination with ropivacaine for interscalene brachial plexus block will yield longer duration of sensory blockade as compared to ropivacaine alone without intravenous or perineural dexamethasone and as compared to ropivacaine and intravenous dexamethasone. This result will suggest that the effect of dexamethasone is a result of direct neuronal activity at the injection site versus systemic absorption.