Optimal analgesia after laparoscopic total hysterectomy with pre-pneumoperitoneum phrenic nerve block using different ropivacaine concentrations: randomized controlled trial

Post-laparoscopic shoulder pain (PLSP) is common after total laparoscopic hysterectomy and can negatively affect recovery. Ultrasound-guided right phrenic nerve block is effective in preventing PLSP, but the optimal concentration of ropivacaine and the best timing for nerve block remain unclear. In this randomized controlled trial, 198 patients undergoing laparoscopic total hysterectomy were allocated into six groups (A1-A3: pre-pneumoperitoneum PNB; B1-B3: PNB at skin closure; n = 33 each), receiving 6 mL of 0.25%, 0.3%, or 0.375% ropivacaine. The primary outcomes were the incidence of PLSP within 72 h and visual analog scale (VAS) pain scores at 0.5 h (T1), 6 h (T2), 24 h (T3), 48 h (T4), and 72 h (T5). Secondary outcomes included rescue analgesic use and postoperative nausea and vomiting (PONV). Multiple comparisons were Bonferroni-corrected (significance: adjusted P < 0.05). Baseline characteristics, including age, Body Mass Index (BMI) and American Society of Anesthesiologists (ASA) physical status classification, were comparable among all groups (P > 0.05). The incidence of PLSP was lowest in group A3 (pre-pneumoperitoneum, 0.375% ropivacaine) at 6.1% (2 of 33), significantly lower than in group A1 (45.5%, χ² = 13.390, P < 0.001; Bonferroni-adjusted P = 0.003) and group A2 (30.3%, χ² = 6.519, P = 0.011; adjusted P = 0.033). In group B3 (skin closure, 0.375% ropivacaine), the PLSP rate was 24.2% (8 of 33), showing marginal significance compared to B1 and B2 (adjusted P = 0.051). At 24 h (T3), VAS scores in A3 were significantly lower than in A1, B1, and B2 (P < 0.05; Bonferroni-adjusted P = 0.10 with three comparisons). At 48 h (T4), scores in A3 remained significantly lower than in B1 and B2 (P < 0.05; adjusted P = 0.10 with two comparisons). No significant differences were observed at T1, T2, or T5 (P > 0.05). Safety outcomes showed no significant differences in intraoperative drug use, rescue analgesic requirement, or PONV incidence (P > 0.05), and no local anesthetic toxicity or serious adverse events were reported. Pre-pneumoperitoneum ultrasound-guided right phrenic nerve block with 0.375% ropivacaine reduced PLSP incidence to 6.1% (adjusted P < 0.05), improved 24–48 h pain control (trend after adjustment), and was well tolerated.