Effect of Intraoperative Intrathecal Morphine on Postoperative Analgesia After Lumbar Spinal Fusion: A Retrospective Comparative Study

AIM: To evaluate the association of intraoperative intrathecal morphine (ITM) with postoperative pain intensity during the first 48 hours after elective posterior lumbar spinal fusion. The secondary aim was to assess its association with cumulative intravenous morphine consumption during the first 24 postoperative hours.
MATRERIAL and METHOD: This retrospective comparative cohort study included 80 adults undergoing elective primary posterior instrumented lumbar or lumbosacral fusion. Forty patients received a single intraoperative dose of 0.15 mg preservative-free ITM, and 40 received no intrathecal opioid (non-ITM). Preoperative and postoperative visual analogue scale (VAS) scores were evaluated at 6, 12, 24, and 48 hours.
RESULTS: Compared with the non-ITM group, the ITM group had lower VAS scores at 6 hours (mean difference, -0.9; 95% confidence interval [CI], -1.2 to -0.6), 12 hours (-1.0; 95% CI, -1.3 to -0.7), and 24 hours (-0.9; 95% CI, -1.2 to -0.5; all p < 0.001). No between-group difference was detected at 48 hours (-0.1; 95% CI, -0.4 to 0.2; p = 0.696). Mean 24-hour intravenous morphine consumption was 20.5 ± 5.3 mg in the ITM group and 30.9 ± 5.6 mg in the non-ITM group, with mean difference of -10.1 mg (95% CI, -12.6 to -7.6; p < 0.001). Postoperative nausea and vomiting, pruritus, and urinary retention did not differ significantly between groups, and no respiratory depression was recorded.
CONCLUSION: Intraoperative administration of 0.15 mg ITM was associated with lower pain intensity during the first 24 postoperative hours and lower 24-hour intravenous morphine consumption after lumbar fusion. The between-group pain difference was no longer evident at 48 hours.