Intrathecal Versus Intravenous Morphine in Minimally Invasive Posterior Lumbar Fusion: A Blinded Randomized Comparative Prospective Study

STUDY DESIGN: A blinded, randomized, comparative prospective study. OBJECTIVE: The aim of this study was to compare the use of intrathecal morphine to endovenous morphine on postoperative pain after posterior lumbar surgery. SUMMARY OF BACKGROUND DATA: Intrathecal morphine can provide significant safe analgesia for at least 12 hours and up to 24 hours in patients undergoing major surgery. Its dosages have been decreasing in the last 30 years, but currently, the optimal dose remains unknown. As of today, there are no studies comparing the efficacy and the side effects of this technique with intravenous morphine administration after minimally invasive lumbar fusion surgery. METHODS: We randomized and compared two groups of 25 patients, who were given either 100 μg intrathecal (ITM group) or 5 ± 2 mg intravenous morphine delivered intravenously for 24 hours at 2 mL/h (IVM group) after minimally invasive posterior lumbar fusion. VAS score at 0, 6, 12, 24 hours, mobilization out of bed at 6 hours, hospitalization duration and complications as lower limbs paresthesia, urinary retention at 6 and 12 hours, nausea, vomit, itch, and constipation were evaluated. RESULTS: Data showed a lower VAS score, a reduction of constipation, lower limbs paresthesia, or urinary retention at 12 hours in ITM rather than in the IVM group. None suffered of vomit, itch, or nausea in both groups. Urinary retention was observed more frequently in ITM group at 6 hours. Patients of ITM group were mobilized out bed earlier than those from IVM group. CONCLUSION: A low dosage of intrathecal morphine is safe and effective after minimally invasive lumbar fusion surgery. The reduction of pain in the study group permitted a shorter hospitalization and earlier mobilization out of bed, augmenting patients' comfort. LEVEL OF EVIDENCE: 2.