Letter to the Editor Regarding ‘Deep Neuromuscular Block Attenuates Chronic Postsurgical Pain and Enhances Long-Term Postoperative Recovery After Spinal Surgery: A Randomized Controlled Trial’

Abstract

Dear Editor, With profound interest we read the article by Tang et al. published in the August issue of Pain and Therapy. In the article, entitled “Deep neuromuscular block attenuates chronic postsurgical pain and enhances long-term postoperative recovery after spinal surgery: A randomized controlled trial”, the authors report the results of a clinical trial comparing the efficacy of intraoperative deep neuromuscular blocks (DNMB) and moderate neuromuscular blocks (MNMB) in reducing the incidence of chronic postsurgical pain (CPSP) and improving recovery following lumbar spinal surgery [1]. Each of the 209 trial participants were diagnosed with a lumbar degenerative condition. The authors determined that DNMB significantly reduced the incidence of CPSP when compared to MNMB, with CPSP occurring in 28.5% of the DNMB group (n = 30/104) and 42.86% of the MNMB group (n = 45/105). In the study, CPSP was defined as postsurgical pain with a VAS score ≥ 4 that persisted for at least 3 months. In terms of secondary outcomes, the DNMB group also saw a significant reduction in acute postsurgical pain when compared to the MNMB group over the first 12 postoperative hours. Additionally, patients’ quality of recovery (as assessed by QoR-15) was significantly higher among the DNMB group at 3 months following surgery. Postoperative opioid consumption was also shown to be reduced among the DNMB group, though this effect was not statistically significant [1]. The authors should be commended for their work in advancing understandings of CPSP prevention, as well as for their assessment of robust secondary outcomes relevant to patients’ quality of life. While we are impressed with the rigor of this article, and the practical applications of its results, we found that there was an area that should be clarified by the authors in order to best contextualize their findings. Though all the participants in the trial had lumbar degenerative diseases, the types of surgeries they received as treatments for said conditions were not constant [1]. In both the DNMB and MNMB groups, some participants had lumbar decompression surgeries that were accompanied by fusion of at least two vertebrae, with the remainder of each group exclusively receiving decompression surgery. Importantly, the proportion of patients that underwent fusion procedures as opposed to decompression alone was not consistent between the DNMB and MNMB groups. In the MNMB group, ~ 82% of participants underwent lumbar fusion (n = 86/105), whereas in the DNMB group, only ~ 75% of participants underwent fusion (n = 79/104). We would like to call attention to the fact that the comparative efficacy of lumbar decompression alone versus lumbar decompression with fusion is a hotly debated subject, with sound evidence present on both sides of the controversy [2, 3]. While fusion is known to improve stability during postsurgical recovery [4], it is also commonly associated with longer operation times, more protracted hospital stays, and more intraoperative blood loss than decompression alone [3, 5]. A 2018 RCT on the topic concluded that decompression alone is usually a more practical approach due to these fusion-associated drawbacks [5], and a 2016 retrospective cohort study recommended fusion only when patients are indicated for instability that would specifically require it, for the same reasons [4]. The two most recent meta-analyses that we found on this topic make contradictory recommendations. Wei et al. 2022, which examined six randomized controlled trials (RCTs) and 27 cohort studies (n = 94,953 total participants analyzed), found no significant differences in patients’ pain, disability scores, or satisfaction with their surgery between lumbar decompression alone and decompression with fusion [2]. As a factor of the observed minimal differences in outcomes between these surgical approaches, Wei et al. posit that decompression alone is more advisable. Conversely, Pranata et al. 2022 found that decompression with fusion was more efficacious than decompression alone in terms of pain and disability outcomes, based on a meta-analysis of three RCTs and ten cohort studies (n = 3993 total participants analyzed) [3]. In light of these opposing perspectives on best approaches for lumbar decompression surgeries, we are interested in whether Tang et al. conducted any subgroup analyses to determine whether the type of surgery received by participants in each group had an effect on postsurgical outcomes, namely CPSP incidence. Releasing an analysis of this sort could help readers gain a more complete understanding of the apparent superiority of DNMB to MNMB in reducing CPSP after lumbar spinal surgeries. While only ~ 6% more of the MNMB group underwent fusion than the DNMB group, we believe that this discrepancy could potentially introduce confounding factors if left unaddressed. If no analysis on the effect of surgery type on focal outcomes has been conducted as of yet, we request that the authors release participant-specific data from this RCT in order to allow other physicians and research groups to make this determination. Publishing this data, or an analysis thereof, would serve the dual purpose of comparing DNMB to MNMB and comparing lumbar decompression alone to decompression with fusion. Despite our concerns surrounding proportional differences in surgery types between the two arms of this RCT, the article is a fundamentally strong piece of research in the pain medicine field, which makes great strides towards understanding and preventing CPSP in the context of lumbar degenerative disease surgeries. CPSP is a persistent global health issue, and research on its prevention has the ability to improve millions of lives. While we are requesting additional analyses from the authors, the benefits of DNMB on postsurgical pain are nonetheless evident, and have been well established previously in the context of laparoscopic surgeries [6, 7]. However, unlike most prior investigations of DNMB versus MNMB on postsurgical outcomes [8], the article by Tang, et al. assesses outcomes that have a significant bearing on patients’ long-term quality of life, including CPSP incidence, daily opioid consumption, and quality of recovery. We congratulate the authors for their specific attention to these too-often-neglected outcomes. We welcome all additional commentary from the authors and other interested persons; this will aid in furthering critical interpretations of this important article. Many thanks to the authors for their valuable contributions.