To the Editor,

By conducting a randomized controlled trial in patients who underwent thoracoscopic lung cancer radical surgery, Xu et al. [1] compared the postoperative analgesic efficacy of ultrasound-guided and thoracoscopy-guided thoracic paravertebral block (TPB) and showed that the thoracoscopy-guided technique needed a shorter procedure time, achieved a higher success rate on the first puncture, and provided more block segments and a longer block duration compared with the ultrasound-guided method. Other than the limitations described by the authors in the discussion section, we noted several issues in this study which would have made the interpretation of their results questionable.

First, the primary outcomes were the procedure time and the success rate on the first puncture for the TPB. In the methods, the authors did not clearly describe if the experience of the anesthesiologist and surgeon who participated in the study in performing the TPB was comparable. To compare effects of different interventions on primary outcomes by a randomized controlled trial, it is essential that the participants are equally proficient with each studied technique to avoid potential bias. We are concerned that an unbalanced experience of anesthesiologist and surgeon in carrying out the TPB would have biased the primary outcomes in favor of the thoracoscopy-guided technique.

Second, this study applied an opioid-dominated postoperative analgesic strategy, that is, patient-controlled intravenously administered sufentanil analgesia with a continuous background infusion dose. Furthermore, a nonopioid basic analgesic, parecoxib, was intramuscularly administered for rescue analgesia when postoperative pain score was greater than five or pain became intolerable. This design does not meet the requirements of the current enhanced recovery after surgery practices for thoracoscopic surgery, in which minimum use of opioid drugs is one of main goals and a multimodal opioid-sparing analgesic strategy is recommended [2]. Although the optimal analgesic combinations remain to be determined, the cornerstone of a multimodal opioid-sparing analgesic strategy is always a series of nonopioid basic analgesics with different mechanisms, such as acetaminophen, nonsteroidal anti-inflammatory drugs, cyclooxygenase-2 specific inhibitors, and others. Furthermore, a combination of nonopioid basic analgesics should be administered as scheduled dosing perioperatively, while opioid analgesics should be administered only as rescue on an “as needed” basis when nonopioid basic analgesics are ineffective or contraindicated [3]. Thus, this design issue may have hindered the generalization of their findings to the current enhanced recovery after surgery practices for thoracoscopic surgery. Most importantly, the authors did not report the total opioid consumption and dosages of rescue parecoxib in the two groups. In the absence of comparison of postoperative analgesic dosages, we argue that the secondary outcomes and their subsequent conclusions, such as postoperative pain scores, duration of regional blocks, and occurrence of adverse events, should be interpreted with caution, as they may have been measured by incomplete methodology.

Finally, the procedure time of the TPB was significantly shortened with the thoracoscopy-guided technique, but the mean between-group difference of procedure time only was 3.5 min. This difference may be statistically significant but clinically insignificant. Moreover, unlike other previous works comparing the performance of different regional blocks [4, 5], this study did not assess the ease of performing the two blocks, though it could be rapidly completed by the operators using a 5-point Likert scale: 1, very difficult; 2, difficult; 3, neutral; 4, easy; and 5, very easy. Thus, we do not agree with the authors’ conclusion that the thoracoscopy-guided technique for the TPB is simpler and more convenient than the ultrasound-guided method.