Editor—We thank Coppens and colleagues1Coppens S. Uppal V. Hoogma D.F. Merjavy P. Rex S. Therapeutic efficacy of intravenous lidocaine infusion compared with thoracic epidural analgesia in major abdominal surgery. Comment on Br J Anaesth 2023; 131: 947–54.Br J Anaesth. 2023; 132: 625-626Abstract Full Text Full Text PDF Scopus (1) Google Scholar for their interest in our study.2Casas-Arroyave F.D. Osorno-Upegui S.C. Zamudio-Burbano M.A. Therapeutic efficacy of intravenous lidocaine infusion compared with thoracic epidural analgesia in major abdominal surgery: a non-inferiority randomized clinical trial.Br J Anaesth. 2023; 131: 947-954Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar We appreciate the concerns raised regarding the potential contradiction of our results with established recommendations favouring thoracic epidural analgesia (TEA) as the first option for analgesic management in major abdominal surgery.3Hughes M.J. Ventham N.T. McNally S. Harrison E. Wigmore S. Analgesia after open abdominal surgery in the setting of enhanced recovery surgery: a systematic review and meta-analysis.JAMA Surg. 2014; 149: 1224-1230Crossref PubMed Scopus (131) Google Scholar In fact, the initial hypothesis within our working group also leaned towards the superiority of TEA over lidocaine in terms of postoperative pain. However, a meticulous review of existing literature revealed consistent evidence supporting the similarity in analgesic benefits between intravenous lidocaine and TEA. This evidence prompted us to design a noninferiority study, acknowledging the associated methodological challenges. The study adhered to the recommendations of the US Food and Drug Administration (FDA) for noninferiority trial design,4https://www.fda.gov/media/78504/downloadGoogle Scholar which establishes that noninferiority is determined as long as the upper limit of the 95% confidence interval of the difference between intravenous lidocaine and TEA is equal to or less than the previously determined noninferiority margin. The predetermined noninferiority margin of 1 for the primary outcome (numerical pain rating scale difference between intravenous lidocaine and TEA at 24 h for dynamic pain) was chosen, considering the psychometric limitations of the numerical pain scale when the difference between techniques is close to 1.5Karcioglu O. Topacoglu H. Dikme O. Dikme O. A systematic review of the pain scales in adults: which to use?.Am J Emerg Med. 2018; 36: 707-714Abstract Full Text Full Text PDF PubMed Scopus (520) Google Scholar Although certain secondary outcomes indicated superiority of TEA over intravenous lidocaine (e.g. greater need for rescue analgesia at 2 h in the intravenous lidocaine group), our primary focus remained on the primary outcome, aligning with the SPIRIT 2013 guidelines.6Chan A.-W. Tetzlaff J.M. Altman D.G. et al.SPIRIT 2013 Statement: defining standard protocol items for clinical trials.Ann Intern Med. 2013; 158: 200-207Crossref PubMed Scopus (3989) Google Scholar However, the study demonstrated the superiority of TEA over intravenous lidocaine in pain management at 24 h (mean 0.53; 95% confidence interval [0.01–1.00]). We concur with the correspondent that any statistical conclusion should resonate with the main result, regardless of secondary outcomes. In addressing intervention blinding, ethical constraints imposed by the Institutional Ethics Committee limited catheter placement to the epidural group, compromising blinding. Our original intention was to place an epidural catheter in all patients regardless of the intervention group, but according to our Institutional Review Board it was not ethical to perform an invasive procedure that would not be used. Nevertheless, efforts were made to ensure patient and treating anaesthesiologist blinding to the greatest extent possible. We informed patients that for those randomised in the epidural group, the catheter would be placed by a physician with more than 5 yr of experience in these procedures, applying the cold sensation test on abdominal dermatomes. One of the issues with TEA is that it is a highly effective technique, but it loses effectiveness over time as a result of catheter exit from the epidural space, displacement or lateralisation, and analgesic failure, among other factors.7Hermanides J. Hollmann M. Stevens M. Lirk P. Failed epidural: causes and management.Br J Anaesth. 2012; 109: 144-154Abstract Full Text Full Text PDF PubMed Scopus (283) Google Scholar Respecting the TEA regimen, the authors are correct in stating that our study did not determine the effectiveness of using patient-controlled epidural analgesia (PCEA). The reason is that, in our setting, PCEA techniques are not used systematically. For this reason, the study conclusion cannot go beyond the use of TEA continuous infusion and cannot be extrapolated to PCEA. Regardless of the analgesia regimen, all patients had non-steroidal anti-inflammatory drugs, paracetamol, or both if they had no contraindications during the 3 days of follow-up. Concerning the type of surgical interventions, the incidental imbalance in Whipple procedures between groups had no attributable factors, with a consistent surgical approach across abdominal procedures (the only difference being time, which we do not consider to be a factor that indicates greater postoperative pain), minimising potential confounding variables. Another point highlighted by the authors is about the trial outcomes. The deliberate choice of dynamic pain as the primary outcome acknowledged its challenging nature in the evaluated surgical procedures. Both static and dynamic pain assessments were reported, offering a comprehensive view of analgesic efficacy. Local anaesthetic toxicity was deemed a secondary safety outcome, and there is inadequate statistical power to ascertain the distinction between groups. Conversely, although we uncovered certain indications that TEA, when compared with intravenous lidocaine, reduces hospital length of stay, it was a secondary outcome. Unfortunately, blinding the surgeons responsible for deciding patient discharge was not feasible, potentially introducing bias to this outcome. A more extensive, blinded, randomised controlled trial with a specific focus on this hypothesis is imperative for further validation of this observed effect. Finally, we acknowledge that the study's results might be startling, but not unprecedented. Although our group recognises flaws in the study, as underscored by the authors of this correspondence,1Coppens S. Uppal V. Hoogma D.F. Merjavy P. Rex S. Therapeutic efficacy of intravenous lidocaine infusion compared with thoracic epidural analgesia in major abdominal surgery. Comment on Br J Anaesth 2023; 131: 947–54.Br J Anaesth. 2023; 132: 625-626Abstract Full Text Full Text PDF Scopus (1) Google Scholar the results are valid and reflect the reality observed in patients subjected to these interventions with these analgesic techniques. Readers ultimately determine whether these results furnish compelling evidence to change their anaesthetic practices. Currently, we are conducting a systematic review of the literature to evaluate the impact of intravenous lidocaine infusion in this and other surgical procedures (PROSPERO 2023 CRD42023392306). The authors declare that they have no conflicts of interest. Therapeutic efficacy of intravenous lidocaine infusion compared with thoracic epidural analgesia in major abdominal surgery. Comment on Br J Anaesth 2023; 131: 947–54British Journal of AnaesthesiaVol. 132Issue 3PreviewEditor—We commend the efforts of Casas-Arroyave and colleagues1 for comparing the efficacy of i.v. lidocaine with thoracic epidural analgesia (TEA) in a multicentre RCT. They concluded that i.v. lidocaine was non-inferior to TEA.Click or tap here to enter text. However, we note that their conclusions face challenges in terms of data support, given that the upper limit of the 95% confidence interval (CI) for the primary outcome measure, the numerical pain rating (NPR) scale on movement, encompasses the prespecified non-inferiority margin of one point on the NPR scale. Full-Text PDF