First, postoperative pain was determined using a visual analog scale (VAS). However, the status of the patients during pain level assessment was not provided. The available literature indicates that pain intensity following bariatric surgery is higher during movement than at rest [3]. We are thus concerned that this unknown factor could have affected the postoperative pain assessment results in this study.

Second, the mean VAS score in the first 24 h postoperatively was higher in patients receiving the TAPB than in those receiving the ESPB. However, we noted that the mean VAS scores during the first 24 h postoperatively in the two groups were < 3, with small standard deviations (2.78 ± 0.34 vs. 2.32 ± 0.12). This indicates that most patients experienced only mild postoperative pain. Furthermore, the maximal between-group difference in the mean VAS scores during the first 24 h postoperatively appeared 20 min after extubation and was < 1. Most importantly, this study did not assess and compare patient satisfaction with postoperative pain control for the TAPB and ESPB. On this basis, we cannot determine whether the greater postoperative pain control reported with the ESPB compared to the TAPB should be considered clinically important.

Third, the authors reported that intravenous nalbuphine was used as the first rescue analgesic and intravenous ketorolac as the second rescue analgesic in cases where the postoperative pain VAS score was ≥ 4, as needed. In the results, the authors only provided total nalbuphine consumption during the first 24 h postoperatively and not ketorolac consumption. We were thus very interested to know whether any of the patients received intravenous ketorolac as a second rescue analgesic. Moreover, when between-group difference in postoperative analgesic consumption has been compared in previous studies assessing the efficacy of different analgesia modalities in patients undergoing bariatric surgery, the dosages of all the analgesics used for postoperative pain control were converted into morphine milligram equivalents in the oral or intravenous form [2]. As the equianalgesic conversion factor of morphine and nalbuphine for postoperative analgesia is approximately 1 : 1.5, the net between-group difference in mean nalbuphine consumption within the first 24 h postoperatively in this study were only equivalent to 2.94 mg intravenous morphine. The available literature recommends that the minimal clinically important difference in morphine milligram equivalents for postoperative pain control be an absolute reduction of 10 mg of intravenous morphine within 24 h [4]. Thus, the clinical significance of postoperative opioid sparing with the ESPB compared to the TAPB is not clearly evident.

Finally, this study assessed the time to first flatus or stool but no other outcome variables of enhanced recovery after surgical protocols for bariatric surgery, such as the incidence of postoperative nausea and vomiting, time to early mobilization, time to hospital discharge, and quality of postoperative recovery [5]. Because of this design limitation, an important question that this study cannot answer is whether the improved postoperative pain control and decreased opioid consumption reported for the ESPB compared to the TAPB can be translated into early postoperative benefits in obese patients undergoing bariatric surgery.