• analgesia
• pain
• postoperative
• nerve block

To the Editor

We read the provocative narrative by Lonnqvist et al 1 entitled ‘Should the ESP block be renamed the RIP II block?’ with great interest. The authors identified numerous parallels between the erector spinae plane block (ESPB) and the almost-forgotten interpleural block, highlighting the abundance of enthusiasm for performance of the ESPB despite a lack of robust scientific evidence to support its effectiveness. While they present many thought-provoking ideas, we would like to present a few counterarguments for the authors’ consideration.

First, the critique of anatomical evidence and comparative studies using a placebo control is typified across regional anesthesia literature. The quadratus lumborum block, as an example, receives a greater volume of journal coverage (140 Pubmed items since 2019), with a comparable proposed mechanism of action, based on similarly diverse cadaveric study outcomes.2 While methodological improvements in cadaveric research may help standardize outcomes, the behavior of embalmed tissue versus living tissue, especially during fascial plane blocks, will always present a challenge in how we translate these findings to the clinical setting.3 We agree that randomized controlled trials (RCTs) comparing blocks against systemic analgesia are ‘stacking the odds’ for a favorable outcome, but this pattern of reporting is commonplace, with very few studies comparing blocks to systemic local anesthetic or wound infiltration, even for a block as heavily reported as the transversus abdominus plane (TAP) block.4

Second, we challenge the idea that the efficacy of an ESPB could be explained by the systemic effects of local anesthetic alone. After changing practice from surgically placed TAP catheters to ESPB catheters for major open hepatobiliary surgery in 2017, we significantly reduced the postoperative morphine consumption and length of stay for our patients despite administering equivalent doses of local anesthetic, which should result in comparable levels from systemic absorption. We also question the logic of equilibrating intravenous lidocaine, which is postulated to exert its clinical effects from mechanisms independent of its sodium channel blockade,5 to the longer-acting local anesthetics used in all the ESPB RCTs included in the referenced meta-analyses. Bupivacaine has never been administered systemically for analgesia to the best of the authors’ knowledge, due to the well-documented and feared complication of local anesthetic systemic toxicity.6

Previously, viable alternatives for postoperative analgesia for thoracic and abdominal surgery were almost entirely neuraxial and associated with catastrophic although rare risks of vertebral canal hematoma, infection and paralysis. Therefore, alternatives were attractive, even if ultimately disappointing. With the advent of ultrasound-guided regional anesthesia, we believe that part of the fascination with fascial plane blocks such as the ESPB stems from perceived ease of performance combined with relative safety when compared with their counterparts. Effectiveness should be established before widespread adoption, but without an association with serious complications, we believe the ESPB will outlive the interpleural block even if we need to wait for more robust evidence of its efficacy.