Reply to Dr Bansal et al

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To the Editor:
We thank Dr Bansal et al1 for their interest in our Daring Discourse.2 In the latter, we speculated that combined infraclavicular-suprascapular nerve blocks (ICB-SSBs) could provide a diaphragm-sparing strategy for shoulder surgery. However, we cautioned readers that initial enthusiasm must be tempered, and randomized trials are required to compare ICB-SSBs to the criterion standard (interscalene blocks).2 In fact, such validation is currently underway in Santiago, Chile ( NCT02993939).
If the results of our upcoming trial reveal that ICB-SSBs provide inferior analgesia to their interscalene counterparts, the road map for future research is clear. The next logical step would be to combine SSB with a costoclavicular instead of a paracoracoid technique for ICB. The former targets the 3 cords of the brachial plexus more proximally (in the costoclavicular space),3 thereby facilitating anesthesia of the lateral pectoral, subscapular, and axillary nerves. Alternatively, formal comparison could be carried out between interscalene and supraclavicular blocks (using a 20-mL injectate and local anesthetic injection posterolateral to the brachial plexus).4 At this stage, we are somewhat hesitant to explore targeted C7 nerve root blocks because of the risk of periforaminal vascular breach.5 However, if hemidiaphragmatic paralysis (HDP), and not analgesia, turns out to be the main issue afflicting combined ICB-SSBs, dose-finding trials should explore the minimal effective volume of local anesthetic required for ICB (and SSB) to cover the shoulder joint while circumventing the risk of incidental phrenic nerve block. Once the optimal diaphragm-sparing analgesic strategy has been elucidated, one will need to determine if it can also provide intraoperative anesthesia. Furthermore, future studies should also investigate the rate of HDP for continuous blockade. While a single-injection technique could initially spare the phrenic nerve, over time, HDP may occur because of local anesthetic accumulation.2
In their comments, Bansal et al1 advocate a combination of cervical plexus, suprascapular, axillary, and Pecs blocks. Conceptually, this strategy is confronted with 2 (prohibitive) shortcomings. First, it ignores the important contribution of the subscapular nerve to the innervation of the rotator cuff.6,7 Second, the strategy of Bansal et al can be used only as a single-shot modality. If inserted preoperatively, axillary catheters interfere with the surgical field, whereas surgical dressings and the presence of hardware (with the attendant infectious concerns) preclude their postoperative insertion.
Nonetheless, we thank Bansal et al for their suggestion. We hope that such discussion provides an omen of things to come. Scientifically and research-wise, we believe that the time has finally arrived for diaphragm-sparing nerve blocks to stand shoulder to shoulder with their quadriceps-sparing counterparts.

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