LAUSR

We thank Pushpanathan and Pawa for their insightful comments [1] on our cadaver study of the paravertebral space [2] We agree that pleural depression is not always seen with injection posterior to the superior costotransverse ligament (SCTL), and that multi-level thoracic paravertebral block (TPVB) requires an injection anterior to the SCTL. We do however question the long-held dogma that the SCTL must be traversed with the needle tip, or that pleural displacement is necessary, to produce a single-level TPVB. We believe that the traditional teaching for multi-level injection (based on the landmark technique) will not reliably place the needle tip several millimeters from the pleura, and within the paravertebral space, hence the need (with a landmark technique) for multiple injections. The recently described retrolaminar PVB [3] and erector spinae plane block [4] involve injections well posterior to the SCTL, and yet would seem to result in paravertebral spread. We concur that injection deep to the SCTL is required for multilevel paravertebral dispersion, and are not suggesting a change of practice to injecting posterior to the SCTL. However, clinicians new to TPVB may be reassured that multiple injections at each level, posterior to the SCTL, could potentially result in successful block without the proximity to the pleura that is still seen by many as a downside to TPVB. More work is needed to further elucidate the mechanisms of local anesthetic spread in TPVB.