Combined Local Anesthetic Infiltration Versus Intrathecal Morphine for Postcesarean Analgesia: A Pilot Randomized Double-Blind Trial

Abstract

Background: This exploratory pilot randomized double-blind trial compared postoperative analgesic outcomes of combined local wound infiltration, rectus aponeurosis infiltration, and intraperitoneal local anesthetic instillation (LWI+RAI+IPLA) with intrathecal morphine (ITM) after cesarean delivery. Methods: Forty-six women undergoing elective cesarean delivery under spinal anesthesia were randomized to receive either ITM (150 µg) or LWI+RAI+IPLA using a bupivacaine–lidocaine–epinephrine mixture. Both groups received standardized spinal bupivacaine–fentanyl and postoperative multimodal analgesia. The primary endpoint was 24-hour rescue morphine consumption. Secondary endpoints included pain scores, time to first rescue opioid request, and opioid-related adverse effects. Results: Rescue morphine consumption was numerically higher with LWI+RAI+IPLA than with ITM, but the difference was not significant (1.3 ± 2.22 vs 0.34 ± 0.98 mg; P = .075). Pain scores at rest and during movement did not differ significantly at any time point. Time to first rescue opioid request was longer with ITM (23.04 hours [95% CI, 21.30-24.79] vs 18.70 hours [95% CI, 15.36-22.04]; log-rank P = .032). Nausea/vomiting was more frequent with ITM but was not significant (30.4% vs 8.7%; P = .135), whereas pruritus was significantly more frequent with ITM (34.8% vs 8.7%; P = .032). No respiratory depression occurred. Conclusion: Twenty-four-hour opioid consumption and pain scores did not differ significantly between groups. Intrathecal morphine prolonged the time to first rescue opioid request, whereas LWI+RAI+IPLA caused less pruritus. Because this pilot study was not powered for equivalence or noninferiority and showed a floor effect in opioid consumption, larger adequately powered trials are needed.