In Reply

Bellew et al. take issue with my statement¹  that the patients reported by Kaufman et al.²  developed “chronic diaphragmatic paralysis that was clearly due to phrenic nerve damage after ISB [interscalene blockade].” However, there was obvious phrenic nerve damage sufficient to cause diaphragmatic paralysis, which usually recovered with treatment of that nerve, and a block had been performed. My statement is a correct summary of the report boiled down to its scientific bare bones. This statement was immediately followed by my comment regarding the Kaufman data that “Few conclusions can be made from a case series with certainty, but their observations support several preliminary hypotheses.” Because I offered only hypotheses on this matter, I suspect that it is actually with these hypotheses that Bellew et al. are uncomfortable. Yet it is established that local anesthetic reaches the phrenic nerve and anterior scalene muscle, that local anesthetic damages nerves and especially muscle, and that muscle damage leads to scaring. Given what is known, it would be surprising if phrenic nerves were not damaged by interscalene local anesthetic injection.

The proposal is offered by Bellew et al. that obesity was a contributing factor. It is worth noting that the body mass indexes of Kaufman’s patients did not differ from the U.S. average. Bellew et al. point out that there may also be surgical risk factors contributing to phrenic nerve damage in cases for which interscalene block is currently used. This is another good reason to seek alternative measures for providing postoperative analgesia in place of interscalene block.