Ultrasound-guided anterior quadratus lumborum block at the L2 level for postsurgical analgesia in patients undergoing laparoscopic gynaecological surgery: a single-centre, randomised, double-blinded trial at a university-affiliated hospital in China

Objective This study aimed to investigate the analgesic effect of an ultrasound-guided anterior quadratus lumborum block (QLB) at the L2 level on postoperative pain after laparoscopic gynaecological surgery.Design Prospective single-centre randomised double-blind trial.Setting University-affiliated hospital.Participants Sixty patients aged between 18 and 65 years scheduled for laparoscopic gynaecological surgery.Interventions Before surgery, bilateral anterior QLB was performed with 20 mL of 0.375% ropivacaine injected on each side in the QLB group, whereas equal amount of saline was administered in the placebo group.Primary and secondary outcome measures The primary endpoint was the cumulative morphine dose in the first 24 hours, and the secondary endpoints were morphine consumption at each time interval, area under the curve (AUC) of the numeric rating scale (NRS) for pain, maximum pain intensity, incidence of moderate-to-severe pain (NRS>3), sedation score, adverse events, and time to home-readiness.Results Cumulative morphine consumption in the first 24 hours after surgery was significantly lower in the QLB group than in the placebo group (mean difference, 14.2; 95% CI 6.3 to 22.1; p<0.001). The AUCs of NRS pain intensity scores, including visceral and incisional pain at rest and on movement, were significantly lower in the QLB group than in the placebo group (all p<0.001). The time to home-readiness was significantly shorter in the QLB group than in the placebo group (p<0.05).Conclusion Ultrasound-guided anterior QLB at the L2 level significantly reduced morphine consumption and relieved visceral and incision pain intensity after laparoscopic gynaecological surgery, which was beneficial for enhanced recovery.Trial registration number Chinese Clinical Trial Registry (ChiCTR-IOR-17011960)