Continuous Interscalene Blocks and Rebound Pain

The number of patients requiring shoulder replacements for many different indications,including osteoarthritis, cuff arthropathy and acute fractures has continually grown inthe last 15 years, as suggested by a recent international meta‐analysis. While there isno designated Canadian database specific to total shoulder arthroplasty compiled by theCanadian Institute for Health Information (CIHI), international data suggests that theexpansion of the indications for reverse total shoulder replacements has contributed tothe increase in the total amount of patients that undergo such procedure, with anestimated growth of 6‐15% between 2011 and 2019. Moreover, there has also been afour‐fold increase in the proportion of outpatient shoulder arthroplasty cases in anACS‐NSQIP database from 2015‐2019, without a notable increase in adverse patient events,highlighting a shift towards a more ambulatory approach to total shoulder arthroplasty(TSA).As this procedure becomes mostly ambulatory, new challenges arise regarding the best painmanagement modality to limit the overall need for opioids and reduce their side effectsincluding respiratory depression, pruritis, nausea and vomiting, as well as increasingpatient satisfaction and recovery. There are multiple anesthetic techniques described inthe literature to aid in multimodal analgesia, the most commonly used being theinterscalene block (ISB), as a single‐shot (sISB) or as a continuous infusion (cISB),often combined with multimodal analgesia with dexamethasone and dexmedetomidine. Othertechniques include superior trunk blocks, as well as suprascapular nerve block, oftenused as an alternative when respiratory complications are a major concern due to phrenicnerve blockade. Most regional analgesia techniques detailed above have shown superiorpain management compared to local infiltration alone.Although the interscalene block is clearly established as standard of care for allpatients undergoing shoulder surgery, numerous studies have compared the efficacy of sISBversus catheter‐based cISB, with variable results favoring either modality in terms ofpain management, opioid consumption and patient‐related side effects. A more recentsystematic review and meta‐analysis of over 1000 patients in 20 trials on the effects ofsingle‐injection vs. continuous brachial plexus blocks for shoulder surgeries onpatient‐reported outcomes published in June 2026 has highlighted better pain managementfor cISB than sISB, especially during the 12‐ to 48‐hour period, although most of theregimens showing better analgesia also included patient‐controlled boluses. Notably, meanpain at rest was lower in the cISB group, with a particular benefit in the 24‐48 hourperiod, a period where the concept of "rebound pain" can occur with single‐shotmodalities.This concept has been defined in some studies as the "the transition from well‐controlledpain (numerical rating scale [NRS] ≤3) while the block is working to severe pain (NRS ≥7)within 24 h of block performance.", with an estimated occurrence of 49.6%. Someidentified contributors were younger patients, female gender, surgery involving bone, theabsence of IV dexamethasone, as well as upper limb surgery. A possible explanation relieson a "supply‐vs‐demand" mismatch, where the possible analgesic block could be ofinsufficient length compared to the patient's needs, especially in the at‐riskpopulations. A study realized in 2007 on femoral nerve block proved that prolonging anerve block with a catheter based infusion did reduce the apparition of rebound pain.This concept has yet to be formally evaluated in upper limb surgeries and blocks,including in total shoulder arthroplasty.