Purpose:

In an effort to control postoperative pain more effectively in spinal fusion patients, intraoperative intrathecal morphine (ITM) administration is gaining popularity and acceptance with clinicians. This study seeks to determine the impact of intraoperative intrathecal opioid (ITO) administration following lumbar fusion surgery on postoperative pain and length of hospitalization as primary outcomes. Secondary outcomes will investigate postoperative opioid intake and side effects.

Methods:

The retrospective analysis of collected data was performed. The study compared patients undergoing one- or two-level transforaminal interbody fusions between 2019 and 2021 who intraoperatively received two different ITO doses (n = 89) vs. the reference group (n = 48) that did not receive ITO. The patients in the ITO group received either 0.2 mg (n = 44) of duramorph or 0.2 mg duramorph + 50 mcg fentanyl (n = 45). The effect of ITO was evaluated for the first four postoperative days (POD) on pain scores (visual analog scale), length of stay (LOS, hours) and opioid requirement (MED, morphine equivalent dose).

Results:

In the ITO group, a significant reduction of postoperative pain scores (t(99) = 4.3, p < 0.001) and opioid intake (t(70) = 2.49, p = 0.015) was noted on POD1. Cohen's d effect sizes were 0.76 and 0.50, meaning that postoperative pain and MED intake were reduced by about ¾ to ½ standard deviations (SD) in the ITO group. Further, multivariate regression models revealed that ITO administration predicted lower postoperative pain scores for the two PODs (β = - 0.83, p < 0.001; β = - 0.63, p = 0.022) and MED intake for the first two PODs (β = - 20.8, p = 0.047; β = - 16.4, p = 0.030). Mean LOS was 15.4 h less in the ITO group (mean ± SD, 63.4 ± 37.1 vs. 78.8 ± 39.6, p = 0.10).

Conclusions:

In conclusion, our study provides results in a large sample of patients undergoing transforaminal lumbar fusions. The results demonstrated that ITO administration is effective in reducing POD1 pain scores and POD1-2 opioid requirement while not increasing the risk of any opioid-related side effects.