Intrathecal Morphine Versus Other Techniques for Postoperative Pain Management in the Context of Multimodal Analgesia: A Meta-Analysis

Objective: Intrathecal morphine (ITM) has been administered in recent years to provide postoperative pain control in non-obstetric surgery; however, current research has limited consideration of the recommendations for regular, basic analgesia from clinical guidelines when exploring its efficacy. This systematic review and meta-analysis aimed to compare ITM against alternative methods of analgesia in the presence of multimodal analgesia, for reducing pain scores within the first 24 h postoperatively. Secondary outcomes included postoperative opioid consumption, incidence of opioid-related effects, and time to mobilisation. Methods: Database searches and screening identified 11 trials for inclusion in this review. Pain scores were compared by meta-analysis at 6, 12, and 24 h postoperatively at rest and on movement, with sub-analysis of systemic versus regional techniques. Results: The data found no significant difference between ITM and active comparators for reducing pain scores at rest or on movement at any of the time intervals explored. Sub-analysis demonstrated that regional techniques may provide superior analgesia at 24 h at rest (MD = −1.19; 95% CI [−1.73, −0.66], p < 0.001, I² = 0%) and on movement (MD = 1.27 [0.44, 2.10], p = 0.003, I² = 0%). Cumulative opioid consumption was reduced in ITM groups (MD = −11.61 [−18.73, −4.50], p = 0.001, I² = 95%), with significantly increased risk of pruritus (p < 0.001) but not nausea and vomiting (p = 0.93). There was no evidence of respiratory depression. Conclusions: This meta-analysis was unable to demonstrate any significant benefit to postoperative pain relief with the use of ITM but may suggest that it is as a viable option compared to other active modalities. However, this meta-analysis was limited by a low quantity and quality of data from which to draw conclusions and demonstrated high statistical fragility. We believe this highlights a significant gap in the current literature on ITM.