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This letter was written in response to the recent article by Xing et al. regarding “Effect of Transcutaneous Electrical Acupoint Stimulation (TEAS) Combined with Transversus Abdominis Plane Block (TAPB) on Postoperative Recovery in Elderly Patients Undergoing Laparoscopic Gastric Cancer Surgery: A Randomized Controlled Trial,” in which the combination of two interventions increased quality of recovery-15 score in early postoperative period, and improved postoperative pain control and immune function.

This letter questioned a few details regarding the method and results of the study conducted by Xing et al., such as inappropriate design of study group, use of non-updated minimal clinically important difference of the quality of recovery-15 score to estimate sample size, clinical significance of pain control improved by TEAS combined with TAPB, and the lack of assessment on important outcome variables of enhanced recovery after surgery for laparoscopic gastric cancer.

This letter aims to clarify the methodological limitations of the study conducted by Xing et al. and improve the interpretation of main findings.

The authors believe that addressing these issues is not only important for design quality improvement of randomized clinical trials comparing perioperative benefits of various interventions, but is also helpful for the readers who want to use an enhanced recovery after surgery protocol, including a combination of TEAS with TAPB in elderly patients undergoing laparoscopic gastric cancer surgery.

To the Editor,

In a single-center double-blind randomized controlled trial with a total of 90 patients undergoing elective laparoscopic gastric cancer surgery, Xing et al. [1] assessed the effect of transcutaneous electrical acupoint stimulation (TEAS) combined with transversus abdominis plane block (TAPB) on the outcomes of postoperative recovery. They showed that TEAS combined with TAPB enhanced early postoperative recovery defined by the quality of recovery-15 (QoR-15) score and improved postoperative pain control and immune function. However, there are several issues in the methodology and results of this study that would have made interpretation of their findings questionable.

First, this was a randomized controlled trial with three arms that were designed to determine the influence of TEAS combined with TAPB on postoperative recovery. However, it was unclear why TEAS without actual electric stimuli was used in the general anesthesia group (G group). The available evidence indicates that use of TEAS alone can significantly enhance postoperative recovery and reduce pain level after laparoscopic surgery [2, 3]. We are concerned that such a blank stimulus design in the G group would have biased their primary outcome in favor of TEAS combined with TAPB group (group NTG). Perhaps, the design of this study can only determine whether TEAS combined with TAPB is superior to use of TAPB (NG group) alone, in term of postoperative recovery outcomes.

Second, the QoR-15 score was the primary outcome of this study, and a difference of at least 8.0 points in the QoR-15 score was considered as clinically significant according to 2016 study of Myles et al. [4]. However, we would like to remind the readers and authors that the minimal clinically important difference (MCID) of the QoR-15 score has been reevaluated and updated to a value of 6.0 by Myles et al. in 2021 [5], as there are significant concerns on the shortcomings of methods used for estimating the MCID of the QoR-15 score in the 2016 study. If a six-point between-group difference was used as the MCID of the QoR-15 score in designing this study, we believe that a greater sample size in each group would be needed.

Third, the visual analog scale (VAS) scores of rest and movement pain levels at 4, 12, and 24 h postoperatively were significantly lower in the NG and NTG groups than in the G group. We noted that the between-group differences in the rest and movement pain VAS scores at all observed points were less than 1. In available literature, the recommended MCID of postoperative pain score is a reduction of 1.5 point on a 0–10 VAS score [6]. The press number of patient-controlled intravenous analgesia pump within 2 days postoperatively was significantly decreased in the NG and NTG groups compared with the G group, but dosages of sufentanil and flurbiprofen axetil for postoperative analgesia were not provided and compared. Thus, it is unclear whether TEAS combined with TAPB can provide a significant opioid sparing for postoperative pain control, i.e., an absolute reduction of 10 mg intravenous morphine in the 24 h [6]. Most important, this study did not determine patients’ satisfaction with postoperative pain control. Because of the above questions, it is very difficult for the readers to determine whether modest improvement of postoperative pain control by TEAS combined with TAPB should be considered as being clinically important.

Finally, this study showed that TEAS combined with TAPB increased the QoR-15 score in an early postoperative period, improved postoperative pain control and immune function, and reduced times to first ambulation and first flatus. Furthermore, an observed period of 7 days after surgery was designed. However, this study did not evaluate other important outcome variables of the current Enhanced Recovery After Surgery practice for laparoscopic gastric cancer surgery, such as the length of hospital stay, incidence of postoperative complications and adverse events, readmission rates within 30 days after surgery, and cost savings [7]. Because of these design limitation, this study cannot answer whether the improvements in immune function, gastrointestinal movement, and quality of postoperative recovery by TEAS combined with TAPB can be translated into the early postoperative benefits of elderly patients undergoing laparoscopic gastric cancer surgery.