Background Currently, the optimal volume of pericapsular nerve group (PENG) block for analgesia after total hip arthroplasty (THA) has not been clarified. In this trial, we investigated whether a high-volume PENG block has a superior analgesic effect than a conventional PENG block for primary THA. Methods Forty patients receiving primary THA under spinal anesthesia were enrolled and randomly divided into the high-volume PENG group (40 mL of 0.375% ropivacaine) and the conventional-volume PENG group (20 mL of 0.375% ropivacaine). Dexamethasone (5 mg) was added to the local anesthetic in both groups. A blinded researcher performed pain scores and lower limb sensory and motor block assessments at 3, 6, and 24 h after surgery. The time of first walking, time of first opioid consumption, total opioid consumption within 48 h, nerve block, opioid-related complications, and length of hospital stay were recorded. The primary outcome was the dynamic pain scores at 6 h post-surgery. Results Thirty-seven patients were included in the final analysis, among whom 18 were in the high-volume group and 19 in the conventional-volume group. There were no significant differences between the two groups in dynamic pain scores at 6h after surgery median and interquartile range (p25, p75) 5(4,6) vs 4 (4,5) and other secondary outcomes. Conclusions The high-volume PENG block is not superior to conventional-volume PENG block in improving post-operative analgesia in patients undergoing primary THA and does not increase the risk of quadriceps weakness. Trial registration Chinese Clinical Trial Registry (ChiCTR, https://www.chictr.org.cn ). Clinical trial registration number: ChiCTR2300077281.
Wang et al. (Fri,) studied this question.