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      The Minimal Clinically Important Differences as Well as Statistical Differences of Main Endpoints are Important in Comparing Postoperative Benefits of Different Analgesic Modalities [Letter]

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      Drug Design, Development and Therapy

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          Dear Editor In a randomized controlled trial including 99 patients who underwent elective laparoscopic bariatric surgery, Sun and colleagues1 showed that both intravenous infusion of lidocaine (IIL) and ultrasound-guided transverse abdominal plane block (UG-TAPB) provided good postoperative recovery and analgesia, but the IIL resulted in better analgesia at 12 h and 24 h postoperatively compared with UG-TAPB. This study has potential implications, but we would like to remind the readers to pay attention to the clinical significance of their findings. First, the Quality of Recovery-40 (QoR-40) score at 24 h after surgery was used as the primary endpoint. In the available literature, a 10-point between-group difference in the total QoR-40 scores is generally considered as the minimal clinically important difference.2 We noted that the total QoR-40 scores were significantly higher in the patients receiving IIL and UG-TAPB compared with the patients receiving the control intervention, but the net between-group difference in the median of total QoR-40 scores was less than 10. That is, the between-group difference in the quality of postoperative recovery is statistically significant, but its clinical significance is not clearly evident. Second, this study assessed the visual analog scale (VAS) score of postoperative pain in the resting state, but not the VAS pain score in the active state. In fact, active pain is more severe than resting pain following bariatric surgery, and effective control of active pain after abdominal surgery is very important for the successful use of enhanced recovery after surgery protocols.3 In this study, the VAS resting pain scores at some time-points after surgery were significantly different among the three groups, but the net between-group differences in mean VAS resting pain scores at all time-points postoperatively were less than 1. We would like to remind the readers that the recommended minimal clinically important differences for postoperative pain scores in the available literature are 1.5 in the resting state and 1.8 in the active state when pain is assessed by a 0–10 VAS score.4 That is, the improvements in postoperative pain control by IIL and UG-TAPB compared with the control intervention do also not exceed the recommended minimal clinically important differences. Finally, intravenous dezocine was applied on demand to maintain a VAS score of 4 or less, and dezocine consumption within 24 h postoperatively was significantly decreased in the patients receiving IIL and UG-TAPB compared with the patients receiving the control intervention. However, when between-group differences in postoperative analgesic consumption are compared, it is generally required that the dosage of analgesic used for postoperative pain control should be converted into morphine milligram equivalents in oral or intravenous form.3,4 Furthermore, it is commonly recommended that the minimal clinically important difference of morphine milligram equivalents for postoperative pain control is an absolute reduction of 10 mg intravenous morphine in the 24 h.4 As the equianalgesic conversion factor of morphine and dezocine is 1,5 the net between-group differences in mean dezocine consumption within 24 h postoperatively in this study are only equivalent to 0.9–5.91 mg intravenous morphine. Accordingly, the real clinical significance of postoperative opioid sparing with IIL or UG-TAPB in this study should be interpreted with caution. We believe that clarification of the above issues will improve the interpretation of findings in this study.

          Most cited references5

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          Minimal clinically important differences in randomised clinical trials on pain management after total hip and knee arthroplasty: a systematic review

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            Efficacy of Ultrasound-Guided Serratus Plane Block on Postoperative Quality of Recovery and Analgesia After Video-Assisted Thoracic Surgery: A Randomized, Triple-Blind, Placebo-Controlled Study

            The optimal regional technique for analgesia and improved quality of recovery after video-assisted thoracic surgery (a procedure associated with considerable postoperative pain) has not been established. The main objective in this study was to compare quality of recovery in patients undergoing serratus plane block (SPB) with either ropivacaine or normal saline on the first postoperative day. Secondary outcomes were analgesic outcomes, including postoperative pain intensity and opioid consumption.
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              Ultrasound-guided transversus abdominis plane (TAP) block for laparoscopic gastric-bypass surgery: a prospective randomized controlled double-blinded trial.

              Despite the laparoscopic approach, patients can suffer moderate to severe pain following bariatric surgery. This randomized controlled double-blinded trial investigated the analgesic efficacy of ultrasound-guided transversus abdominis plane (TAP) blocks for laparoscopic gastric-bypass surgery. Seventy patients undergoing laparoscopic gastric-bypass surgery were randomized to receive either bilateral ultrasound-guided subcostal TAP block injections after induction of general anesthesia or none. All patients received trocar insertion site local anesthetic infiltration and systemic analgesia. The primary outcome was cumulative opioid consumption (IV morphine equivalent) during the first 24 h postoperatively. Interval opioid consumption, pain severity scores, rates of nausea or vomiting, and rates of pruritus were measured during phase I recovery, and at 24 and 48 h postoperatively. There was no difference in cumulative opioid consumption during the first 24 h postoperatively between the TAP (32.2 mg [95% CI, 27.6-36.7]) and control (35.6 mg [95% CI, 28.6-42.5]; P = 0.41) groups. Postoperative opioid consumptions during phase I recovery and the 24-48-h interval were similar between groups, as were pain scores at rest and with movement during all measured intervals. The rates of nausea or vomiting and pruritus were equivalent. Bilateral TAP blocks do not provide additional analgesic benefit when added to trocar insertion site local anesthetic infiltration and systemic analgesia for laparoscopic gastric-bypass surgery.

                Author and article information

                Drug Des Devel Ther
                Drug Des Devel Ther
                Drug Design, Development and Therapy
                20 September 2022
                : 16
                : 3195-3196
                [1 ]Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University , Beijing, People’s Republic of China
                Author notes
                Correspondence: Fu-Shan Xue, Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University , No. 95 Yong-An Road, Xi-Cheng District, Beijing, 100050, People’s Republic of China, Tel +86-13911177655, Fax +86-10-63138362, Email xuefushan@aliyun.com; fushanxue@outlook.com
                Author information
                © 2022 Tian et al.

                This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms ( https://www.dovepress.com/terms.php).

                : 11 April 2022
                : 07 September 2022
                Page count
                Figures: 0, References: 5, Pages: 2

                Pharmacology & Pharmaceutical medicine
                Pharmacology & Pharmaceutical medicine


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