A Double-Blind Randomized Comparison Trial of Postoperative Pain in Patients Undergoing Total Shoulder Arthroplasty Who Receive Interscalene Blocks With or Without Liposomal Bupivacaine (PoPTSAWoW Trial)

Patients undergoing shoulder surgery can suffer from significant postoperative pain which can lead to an increase in recovery time, opioid use and potential dependency, and a decrease in quality of recovery. The interscalene brachial plexus block is a common effective regional anesthesia technique used for a variety of procedures involving the shoulder. The number of total shoulder arthroplasty surgeries being performed annually in the United States are increasing every year. Liposomal bupivacaine was FDA approved for use in patients undergoing interscalene block in 2018 to reduce postoperative pain from shoulder surgery. The information from the manufacturer indicates that the liposomal encapsulation may release the drug for up to approximately 72 hours after it has been administered, providing a prolonged analgesic effect. Evidence to the prolonged analgesic effect of liposomal bupivacaine has varied in the current literature. A recent meta-analysis suggested that liposomal bupivacaine may provide a statistically significant, but clinically insignificant decrease in opioid consumption and pain scores over time. The authors noted a possible limitation of their study is that the meta-analysis included a variety of surgical procedures and block techniques, and was not specific to shoulder surgery or interscalene block. The authors noted that this variability in anesthetic regimens between study groups could have affected the observed outcomes.

Recently, the investigators performed a retrospective quality improvement study to investigate the potential benefit of liposomal bupivacaine used for interscalene blocks among 491 patients undergoing shoulder arthroplasty between 2018 and 2021. The investigators compared the difference in the proportion of patients with clinically tolerable pain scores (defined as VAS ≤ 4) in those patients receiving liposomal bupivacaine vs. those receiving another local anesthetic (plain bupivacaine, mepivacaine or ropivacaine) vs. those receiving no block. The results of this study suggested there was significant difference in the proportion of patients with clinically tolerable pain scores when receiving liposomal bupivacaine during all observations and at 3 days postoperatively versus those patient that did not. The patients who received liposomal bupivacaine also had a significant reduction in morphine milligram equivalents (MMEs).

Based on the investigators retrospective results, the investigators performed a power analysis which allowed for the development of this prospective randomized double blinded trial comparing liposomal bupivacaine plus plain bupivacaine vs. plain bupivacaine only in near equipotent doses. The investigators believe that this is a very important and unique trial to perform as it could change the way pain management is delivered in this patient population. Longer acting local anesthetic used for interscalene blocks may increase the number of patients who have tolerable pain and require less or no opioids. This could reduce or inevitably eliminate the unwanted effects of opioids (nausea, vomiting, constipation, urinary retention, opioid induced respiratory depression, dependency and addiction) and result in an improvement in the quality of recovery of patients undergoing total shoulder arthroplasties.