To the Editor:
We read with great interests the article “Superior Trunk Block: A Phrenic-sparing Alternative to the Interscalene Block: A Randomized Controlled Trial” by Kim et al.1 The superior trunk block is a promising alternative to interscalene brachial plexus block with diaphragm-sparing. We appreciate the authors’ great work, but we do have several concerns. First, the cutaneous innervation of shoulder is provided by brachial plexus and supraclavicular nerves which originate from superficial cervical plexus2 ; therefore, to carry out shoulder surgery solely with peripheral nerve blocks, brachial plexus block must be combined with superficial cervical plexus or supraclavicular nerve block to provide coverage for skin incision and closure.3 In this study, consequent intravenous sedation was provided intraoperatively, but superficial cervical plexus, supraclavicular nerve block, or local anesthetic infiltration at the surgical sites was not performed. Second, the unit of grip strength measurement in this article was not provided. We speculate that the unit should be kilogram according to their previous study.4 The grip strength after block was described as change from baseline in this article rather than proportion of baseline by Auyong et al.5 We consider the latter description of grip strength a better strategy to make comparisons. According to their previous baseline data of grip strength, we speculate that the grip strength after interscalene plexus block was about 42% of baseline in this study, which is higher than 27% by Auyong et al.5 It would be hard to preserve such a high proportion of baseline grip strength with 0.5% bupivacaine 15 ml deposited in between C5 and C6 nerve roots. Thirdly, there are existent studies by Aliste et al.6,7 showing that targeting the brachial plexus causes a hemidiaphragmatic paralysis rate of less than 5%. Finally, it is illogical that under intravenous sedation, the intraoperative mean minute ventilation measurements have even increased in the superior trunk group compared with baseline.
Competing Interests
The authors declare no competing interests.