Abstract
BACKGROUND: 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. METHODS: In this randomized controlled trial, 198 patients undergoing laparoscopic total hysterectomy were allocated into six groups (A(1)-A(3): 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 (T(1)), 6 h (T(2)), 24 h (T(3)), 48 h (T(4)), and 72 h (T(5)). Secondary outcomes included rescue analgesic use and postoperative nausea and vomiting (PONV). Multiple comparisons were Bonferroni-corrected (significance: adjusted P < 0.05). RESULTS: 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 A(3) (pre-pneumoperitoneum, 0.375% ropivacaine) at 6.1% (2 of 33), significantly lower than in group A(1) (45.5%, χ² = 13.390, P < 0.001; Bonferroni-adjusted P = 0.003) and group A(2) (30.3%, χ² = 6.519, P = 0.011; adjusted P = 0.033). In group B(3) (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 (T(3)), VAS scores in A(3) were significantly lower than in A1, B1, and B2 (P < 0.05; Bonferroni-adjusted P = 0.10 with three comparisons). At 48 h (T(4)), scores in A(3) remained significantly lower than in B(1) and B(2) (P < 0.05; adjusted P = 0.10 with two comparisons). No significant differences were observed at T(1), T(2), or T(5) (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. CONCLUSION: 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. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12871-025-03391-6.