Perineural or intravenous administration of dexmedetomidine combined with anterior quadratus lumborum block for analgesia after retroperitoneal laparoscopic surgery: a prospective, randomized controlled trial

PURPOSE: The duration of a single anterior quadratus lumborum block (QLB) cannot fully meet the postoperative analgesic needs of patients undergoing retroperitoneal laparoscopic surgery. We investigated whether perineural or intravenous dexmedetomidine (Dex) administration combined with anterior QLB could improve analgesic efficacy. METHODS: Ninety-six patients were randomized, and 88 were included in the modified per-protocol analysis. A total of 88 patients scheduled for retroperitoneal laparoscopic surgery under general anesthesia combined with anterior QLB were randomly assigned to one of three groups: (1) control group (R): 0.375% ropivacaine 30 mL; (2) ropivacaine plus perineural Dex (RD): 0.375% ropivacaine 30 mL plus 1 µg/kg Dex, (3) ropivacaine plus intravenous Dex (RDiv): 0.375% ropivacaine 30 mL plus intravenous 1 µg/kg Dex. The primary outcome was the 48 h postoperative sufentanil consumption. Secondary outcomes included Numerical Rating Scale (NRS) scores at different postoperative time points, intraoperative hemodynamic parameters, and adverse effects. RESULTS: The 48 h postoperative sufentanil consumption was significantly lower in group RD than in groups R and RDiv [median (IQR): 31.0 (16.3, 39.0) vs. 40.1 (27.2, 60.7) vs. 42.0 (31.5, 57.9); adjusted P < 0.05, Bonferroni post-hoc test], with between-group differences of -17.2 µg (95%CI -23.4 to -11.3) and - 16.7 µg (95%CI -23.2 to -10.8). Fewer patients in group RD (14% vs. 40% vs. 34%; P = 0.069) required rescue analgesia, though the difference did not reach statistical significance. Group RD exhibited significantly lower resting and dynamic NRS pain scores at key postoperative time points (P < 0.05). QoR-15 was statistically higher in group RD, although the between-group difference was below the reported minimal clinically important difference (MCID). Dexmedetomidine was associated with lower MAP and HR at selected intraoperative time points, without a statistically significant increase in postoperative bradycardia or hypotension. No significant differences were observed among the three groups in adverse events, time to first flatus, ambulation, or length of stay( all P > 0.05). CONCLUSIONS: Perineural administration of 1 µg/kg dexmedetomidine combined with anterior QLB could provide better postoperative analgesia, which reduced 48-hour postoperative sufentanil consumption and improved pain scores at several time points. However, intravenous dexmedetomidine at the same dose did not confer comparable benefits in this setting. TRIAL REGISTRATION: Chinese Clinical Trial Registry (ChiCTR2300074778) Registration date 16/08/2023.