Erector Spinae Versus Paravertebral Nerve Blocks for Breast Surgery

Following painful surgical procedures of the breast, postoperative analgesia is often provided with a paravertebral nerve block (PVB). For intense, but shorter-duration acute pain, a single-injection of local anesthetic is used with a duration of approximately 12 hours. The PVB has several limitations: it can decrease blood pressure, and very rare-but serious-complications have occurred, including neuraxial injection, neuraxial hematoma, and pleural puncture. An alternative block has been described: the erector spinae plane block. The theoretical benefits include ease of administration since it is a plane superficial to the PVB and therefore easier to identify and target with ultrasound (therefore increasing success rate); and an increased safety margin: there are few anatomic structures in the immediate area which could be injured with the needle; and, the target plane is much further from the intrathecal/epidural space relative to the PVB. Lastly, the plane may be easier to catheterize for continuous peripheral nerve blocks relative to the relatively-small volume PVB. There are therefore multiple theoretical reasons to prefer the erector spinae plane block. Unfortunately, it remains unknown if the analgesia provided by this new technique is comparable to that provided with the PVB. The investigators therefore propose to compare these two techniques with a randomized, subject-masked, active-controlled, parallel-arm, human subjects clinical trial.