Postoperative analgesic effectiveness of ultrasound-guided bilateral erector spinae plane block

Abstract

While the study of Urmale Kusse et al. [1] makes a valuable contribution to the topic, I believe that several aspects warrant further discussion.

First, the sample size was based on a randomised controlled trial investigating postoperative analgesia in patients undergoing laparoscopic cholecystectomy [2]. The trial compared rectus sheath block with rectus sheath block and erector spinae plane block, which differs from the comparison in the current study. Thus, using this reference to calculate the sample size may not be appropriate. Additionally, the blinding in this study presents challenges, as the puncture sites for erector spinae plane block and rectus sheath block are located on the back and abdomen, respectively, compromising blinding for both patients and postoperative caregivers. The inclusion of placebo or sham blocks would have improved blinding.

Second, regarding the evaluation of postoperative analgesic outcomes, the study measured total opioid consumption and converted the 24-h opioid use into standardised morphine milligram equivalents (MME). The results showed mean (SD) opioid consumption of 3.5 (8.7) MME in the erector spinae plane block group vs. 8.2 (2.8) MME in the rectus sheath block group (p = 0.003). However, the minimum clinically important difference for 24-h postoperative opioid consumption is 10 MME [3], indicating that the observed difference between the two groups did not meet this threshold. I believe this may be attributed to the analgesic protocol employed, which involved administering medication based on pain assessment rather than patient-control. This approach may have resulted in delayed opioid administration, potentially compromising pain control, as a significant proportion of patients experienced moderate to severe pain (NRS 4–7) postoperatively. This could be related to the constraints typical of low- and middle-income settings.

Finally, I have concerns regarding the timeline of the nerve block procedures. Both blocks were performed while patients were anaesthetised. While rectus sheath block can be administered with the patient in a supine position, erector spinae plane block requires the patient to be in the lateral decubitus position. This necessitates repositioning the anaesthetised patient from supine to lateral and then back to supine, which is complex and time-consuming. However, the reported mean (SD) anaesthesia duration of 164 (16) min for the erector spinae plane block group and 159 (14) min for the rectus sheath block group; and the surgery duration of 150 (14) min for the erector spinae plane block group and 143 (18) min for the rectus sheath block group, do not indicate a longer non-surgical anaesthesia time for the erector spinae plane block group.