If Wishes Were Horses, Beggars Would Ride

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To the Editor:
We congratulate Vandepitte et al1 on their study comparing liposome bupivacaine with standard bupivacaine in interscalene brachial plexus blocks for major shoulder surgery. The pharmacological profile of liposome bupivacaine offers the potential to provide longer-lasting analgesic effects, and this is the first study to compare it directly with single-shot interscalene block in a representative patient group. The complexity of managing nerve catheters is well known, and as such, the outcome of this study has been eagerly awaited; however, we feel it is important to clarify the authors' conclusions.
First, it should be emphasized that this is a negative study. The primary outcome stated was worst pain in the first postoperative week, using a 3-point difference in the numeric rating scale at postoperative day 2 as the clinically important difference to detect. Patients had moderate to severe pain at baseline, which was treated, in more than 50% of patients, with multimodal analgesia. This baseline pain did not improve by much postoperatively in either group and did not correlate with reduced opioid consumption or sleep disturbance. The authors state that there was a modest reduction in worst pain in the liposome bupivacaine group, but they do not explicitly state that they had not achieved their primary outcome. According to the authors' own powering, this nonsignificant difference could be explained by chance.
Second, the patient group chosen was undergoing moderate to severely painful surgery, which, in North America, would most often be managed with a catheter technique and local anesthetic infusion, rather than a single-shot nerve block.2 This leads us to question whether the control methodology is adequate. We do appreciate, however, that a single-shot technique may be the standard at their institution and that a noninferiority trial versus standard catheter technique may have been premature at this dose-finding stage, especially given no improvement seen in the primary outcome measure compared with standard bupivacaine.
Third, it was positive that there were no significant differences in motor block or functionality of the arm, as it would have been concerning if there was prolonged analgesia, accompanied with a fully paralyzed limb! However, this could also suggest that the liposome bupivacaine was not as effective as hoped, and we wonder why the authors used 0.25% bupivacaine, as opposed to a higher-mass solution, especially considering this is a low-volume block.
Overall, this study has not demonstrated a clear benefit of liposome bupivacaine over multimodal analgesia with a standard local anesthetic. While we all wish for a long-lasting local anesthetic for single-shot blocks, with minimal motor blockade, it seems from this study that the search continues.

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