Intrathecal morphine dose optimization in robotic-assisted laparoscopic hysterectomy: a dual-center cohort study

Background: Optimized perioperative analgesia is a critical component of Enhanced Recovery After Surgery (ERAS) pathways in robotic-assisted laparoscopic hysterectomy (RALH). In high-volume robotic programs, predictable pain control may influence early mobilization, postoperative stability, and discharge planning. This study evaluated the analgesic efficacy and safety of two low-dose intrathecal morphine (ITM) regimens (0.10 mg vs. 0.15 mg) in patients undergoing RALH. Methods: We conducted a retrospective dual-center cohort study including 100 women who received spinal anesthesia with 0.10–0.15 mg of preservative-free intrathecal morphine, with or without levobupivacaine, prior to general anesthesia for RALH. Postoperative pain was assessed using the Visual Analog Scale (VAS) at three time points (PACU arrival, PACU discharge, and 24 h postoperatively). Rescue opioid use, hemodynamic events, postoperative nausea and vomiting (PONV), pruritus, and recovery parameters (Alderete Score) were recorded. Comparative analyses were performed between the two ITM dose groups. Results: Pain scores remained consistently low across all time points (median VAS = 0; p = 0.302), with rescue analgesia required in 7% of patients (n = 7/100). Compared with the 0.10 mg group, the 0.15 mg group demonstrated significantly lower pain scores and reduced supplemental opioid requirements. Higher rates of pruritus, PONV, and hypotensive episodes were observed in the 0.10 mg group. No cases of respiratory depression or prolonged PACU stay were recorded. Median Alderete Scores were consistently optimal (10/10), indicating stable postoperative recovery. Conclusion: Low-dose intrathecal morphine provides effective, opioid-sparing, and motor-preserving analgesia in robotic-assisted laparoscopic hysterectomy. In this cohort, the 0.15 mg regimen was associated with improved analgesic balance without an increase in clinically significant adverse events. Within ERAS-based robotic pathways, optimized intrathecal morphine dosing may support predictable recovery and perioperative stability. Observational design precludes causal inference. Prospective randomized studies are warranted to confirm these findings. Trial registration: The Ethics Committee approved the study (Protocol ID 3307/2020) on July 6th, 2020, and it was registered in clinicaltrial.gov (NCT07169604).