Comparing Analgesic Efficacy of Regional Block Techniques After Laparoscopic Liver Resection: In Reply [Response to Letter]

Dear editor

We thank Dr. Nong He et al for their comments on our study. First, we agree that the distinction is important when designing, or interpreting the results of clinical trials. However, we disagree that the minimal clinically important difference (MCID) should dictate the effect size used in a sample size calculation for a clinical trial.¹ The chosen effect size should be clinically or scientifically meaningful, but it need not be the MCID.² In addition, the recommended MCIDs of 10 mg IV morphine reduction for 24 h is for total hip arthroplasty or total knee arthroplasty,³ not for liver resection.

Second, most patients complained of severe abdominal pain or discomfort when they were admitted to the PACU (ie, at emergence) which led to demands for additional opioid analgesics. So, the highest pain score was mostly detected at the time of PACU admission as shown in Figure 2,⁴

Figure 2 Numeric rating scale (NRS) scores at rest for the two groups within 72 hours postoperatively. P values result from a Bonferroni correction for multiple comparisons.  Abbreviations: ESP, erector spinae plane; QL, quadratus lumborum. Notes: Reproduced from: Kang R, Lee S, Kim GS, et al. Comparison of Analgesic Efficacy of Erector Spinae Plane Block and Posterior Quadratus Lumborum Block in Laparoscopic Liver Resection: A Randomized Controlled Trial. J Pain Res. 2021;14:3791–3800. doi: 10.2147/JPR.S343366.4 © 2021 Kang et al. Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/).

and this severe pain may reflect significant visceral pain in addition to somatic pain. Although there is evidence that paravertebral or epidural spread can occur after facial plane blocks such as erector spinae plane block or quadratus lumborum block, it is not clear how consistently and to what extent this occurs, so it may not completely cover the visceral pain in our patients after hepatectomy.⁵

In our institution, postoperative pain management in the general ward was performed by the surgical team. We agree that postoperative pain management should be more refined to improve patient recovery. We also agree that repeated measurement of the QoR-15 questionnaire might be better to elucidate the quality of recovery between two peripheral nerve blocks. However, the QoR-15 score was the secondary outcome of this study, and we were more focused on the primary outcome (ie, cumulative opioid consumption) under the constraints such as limitations in time and manpower.