Is Thoracic Paravertebral Block Truly Superior to Erector Spinae Plane Block? Re-Evaluating the Evidence from a Recovery Perspective [Letter]

We read with great interest the randomized controlled trial (RCT) by Shi et al comparing ropivacaine-based thoracic paravertebral block (TPVB) with erector spinae plane block (ESPB) on quality of recovery in laparoscopic colorectal cancer surgery, recently published in Drug Design, Development and Therapy. 1 We commend the authors for conducting this timely and clinically relevant investigation; as the adoption of enhanced recovery after surgery (ERAS) pathways accelerates in colorectal surgery, defining the optimal regional analgesic strategy remains a priority.That said, we would like to raise three points that we believe merit closer attention: the anatomical basis for the chosen block level, the use of per-protocol instead of intention-to-treat analysis, and how to interpret clinical significance alongside statistical significance. Anatomical Considerations for Block Level SelectionThe authors performed both TPVB and ESPB at the T10 level, with 20 mL of 0.375% ropivacaine injected per side.Technically this is sound, but a single-level injection may not cover the full range of nociceptive pathways activated during colorectal surgery.Somatic pain from abdominal incisions travels via the T8-T12 intercostal nerves, whereas visceral pain from the colon and rectum is carried by the celiac and superior hypogastric plexuses.In addition, low rectal or pelvic dissection engages the parasympathetic pelvic splanchnic nerves (S2-S4). 2 Previous studies indicate that a single TPVB injection of 20 mL local anesthetic typically spreads over four to five dermatomes, which could leave both cephalad and caudad nociceptive inputs only partially blocked. 3Similarly, although ESPB was originally described for thoracic neuropathic pain, 4 its spread mechanism and extent remain variable.Anatomical and histotopographic studies have shown that injectate distribution within the erector spinae plane is inconsistent; lateral and anterior spread depend on fascial integrity and on the needle tip's precise position relative to the costotransverse foramina. 5onsequently, a single injection at T10 risks inadequate anesthesia of the T8-T9 dermatomes, the periumbilical region, and -crucially for low anterior resection -the pelvic and sacral nociceptive afferents.Incomplete cephalad, caudad, or pelvic nociceptive coverage is a possible explanation for the modest between-group differences observed in this trial, though this mechanism was not directly measured.For future studies, we suggest that researchers consider a multi-level injection strategy, combine ESPB with a block targeting the abdominal wall or pelvic plexus, or explore alternative truncal blocks such as the quadratus lumborum block (QLB). Methodological Rigor: Intention-to-treat versus Per-protocol AnalysisOur second point concerns the analytical framework used in this trial.The primary efficacy analysis was performed on the per-protocol (PP) population, after two participants were excluded post-randomization -one due to block failure and