Therapeutic effect of intrathecal morphine after posterior lumbar interbody fusion surgery: a prospective, double-blind, randomized study.

STUDY DESIGN: Prospective, double-blind, randomized, placebo-controlled study.

OBJECTIVE: To assess the efficacy and safety of 0.4 mg intrathecal morphine for postoperative pain control after posterior lumbar interbody fusion (PLIF) surgery.

SUMMARY OF BACKGROUND DATA: Multiple studies have established the technique of intrathecal morphine analgesia in a wide variety of clinical settings. Several trials were conducted in patients undergoing spine surgery, generally supporting the efficacy for this type of surgery. Many exhibit methodologic problems with dosing regimes or study design.

METHODS: After the institutional review board-approval and written informed consent, 52 patients scheduled for PLIF-surgery were enrolled, of whom 46 could be analyzed. Patients were randomized to receive 0.4 mg morphine (M-group) or normal saline (P-group) intrathecally under direct vision before the end of surgery. Additionally, all patients received a piritramide patient-controlled-analgesia for individual pain control. Measures included visual analog scale-scores and blood-gas analysis over 20 hours after surgery. Morphine associated side effects and complications were recorded.

RESULTS: Visual analog scale-scores at rest and when the patients bent their legs were comparable between groups throughout the observation period, only being significantly lower in the M-group at rest 4 and 8 hours after surgery. Cumulative piritramide patient-controlled-analgesia requirements were significantly lower in the M-group throughout the observed 20 hours after surgery. Patients of the M-group were experiencing mild respiratory depression 4 hours after surgery not demanding any intervention, though. With respect to other morphine associated side effects or complications, there was no difference between the study groups.

CONCLUSION: We demonstrated the efficacy of 0.4 mg intrathecal morphine after PLIF-surgery as indicated by a significantly lower cumulative piritramide requirement without any serious increase of opioid associated side effects. Therefore, morphine in a dose of 0.4 mg administered intrathecally seems to be a viable alternative therapeutic option to provide postoperative analgesia with PLIF-surgery.