A Prospective Triple-masked Randomized Controlled Trial Measuring Analgesia Duration of Dexamethasone, Buprenorphine, or Clonidine With Ropivacaine for Interscalene Nerve Block

This is a prospective randomized controlled triple-masked study looking at the duration of nerve block analgesia when using the listed adjuvants (dexamethasone, buprenorphine and clonidine) plus ropivacaine versus plain ropivacaine alone. This will be looked on on patients undergoing painful shoulder surgery in the ambulatory surgery center. Patients will be randomized to one of four groups (1. 0.75% plain ropivacaine. The reference comparator 2. A mixture of 0.75% ropivacaine with 300 mcg buprenorphine 3. A mixture of 0.75% ropivacaine with 75 mcg clonidine 4. A mixture of 0.75% ropivacaine with and 8mg dexamethasone) for their regimen in the interscalene block for their surgery. The patients will then be called within 3 days post-operatively to follow-up. Follow-up data collected will be when did the patient experience return of pain to the operative limb (duration of analgesia), when did the patient experience return of motor function of the operative limb (duration of motor block) and when did the patient experience return of sensation of the operative limb (return of sensory block). All three of these adjuvants have been studied previously and shown to have increased analgesic duration with local anesthesia, but have never had a good comparative study. The mechanism of action of the analgesia for these adjuvants pain relief has never been shown although it is likely a indirect effect as there are animal studies looking at their effect on A and C fibers that did not show those results.