Dear Editor
We read with great interest the trial by Fang et al. [1] evaluating dexamethasone as an adjuvant to continuous erector spinae plane block (ESPB) for analgesia after video-assisted thoracoscopic surgery. This study addresses an underexplored question, as few rigorous trials have examined adjuvants in continuous regional catheter infusions, and the multidimensional outcome assessment incorporating the QoR-15 scale, chronic postsurgical pain follow-up, and inflammatory biomarkers represents a commendable design. Nevertheless, we wish to raise several methodological concerns that may affect the interpretation of the findings.
First, the clinical significance of the primary outcome warrants careful consideration. The observed mean difference in resting VAS at 12 h was 0.68 points, below the 1.0-point minimal clinically important difference (MCID) threshold that the authors themselves cited. Although the reported Cohen’s d of 0.61 suggests a medium effect, statistical effect sizes and patient-perceived thresholds serve different functions and should not be conflated. Moreover, MCID values for postoperative VAS vary across surgical populations and require cautious interpretation [2]. We acknowledge this finding should not be examined in isolation, as significant reductions in tramadol consumption and rescue analgesia suggest a broader analgesic benefit. However, this simultaneously raises the question of whether VAS at a single time point was the optimal primary endpoint, and whether a composite or cumulative pain measure would have better characterized the clinical impact of the intervention.
Second, the study design cannot distinguish between perineural and systemic effects of dexamethasone. In this trial, 10 mg of dexamethasone was infused continuously over 72 h via the ESPB catheter, resulting in sustained systemic absorption. The dexamethasone plus continuous ESPB(D + C-ESPB) group exhibited significantly elevated blood glucose and reduced lymphocyte counts at 48 h, consistent with systemic glucocorticoid activity. Without an intravenous dexamethasone control group, it is impossible to attribute the analgesic benefits to a local mechanism. Two recent meta-analyses demonstrated that intravenous dexamethasone produces comparable analgesic prolongation to perineural administration, with one network meta-analysis of 118 studies finding no difference between routes after bias adjustment [3,4]. These findings suggest the reported benefits may have been achievable through intravenous administration alone.
Third, there is a discrepancy in the analytical approach. The authors stated that all 90 randomized participants were included in the intention-to-treat (ITT) analysis, yet all reported results derive from the per-protocol population of 85 patients. Five patients were excluded for catheter-related complications and protocol deviations, events potentially related to the intervention. In a superiority trial, per-protocol analysis alone risks overestimating treatment effects by excluding patients who fared poorly, compromising randomization’s protective balance [5]. The absence of true ITT results represents a deviation from CONSORT standards.
In summary, while the concept of enhancing continuous ESPB with adjuvants is promising and this trial offers valuable preliminary evidence, the conclusions should be interpreted with caution given the above concerns. Future three-arm studies including an intravenous dexamethasone group, powered to detect clinically meaningful differences, would clarify the role of perineural dexamethasone in continuous regional analgesia.
Acknowledgements
Fan Mo: Writing – original draft; Yuanhong Xu: Conceptualization; Zhaohui Song: Writing – review & editing.
Funding Statement
No funding was received for this work.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
Data sharing does not apply to this article as no new data were created or analysed in this study.
References
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This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
Data sharing does not apply to this article as no new data were created or analysed in this study.