Introduction: Despite the potential for faster postoperative recovery and the ease of direct intraoperative injection into the exposed dura, intrathecal morphine is rarely provided in lumbar spine surgery.

Methods: In this double-blind trial, we randomly assigned 150 patients undergoing instrumented lumbar fusion for degenerative indications to receive a single intrathecal injection of morphine (0.2 mg) or placebo (normal saline) immediately prior to wound closure. An oblique injection technique was used to reduce the risk of precipitating a cerebrospinal fluid leak. The primary outcome was pain measured on the visual-analogue scale during the first 24 hours after surgery. Secondary outcomes included respiratory depression and treatment-related side effects. An intention-to-treat, repeated-measures analysis was used to estimate outcomes.

Results: The baseline characteristics of the groups were similar. Intrathecal morphine reduced pain both at rest (32% area under the curves [AUCs] difference, P<0.002) and with movement (22% AUCs difference, P<0.02) during the initial 24 hours after surgery. The risk of respiratory depression was not increased by intrathecal morphine (hazard ratio, 0.86; 95% confidence interval, 0.44 to 1.68; P=0.66). Postoperative opioid requirements were reduced with intrathecal morphine (P<0.03). Other than a trend towards increased intermittent catheterization in patients assigned to intrathecal morphine (P=0.09), treatment-related side effects did not significantly differ between the groups. The early benefits of intrathecal morphine on postoperative pain were no longer apparent after 48 hours.

Conclusions: A single intrathecal injection of 0.2 mg of morphine safely reduces postoperative pain following lumbar fusion. (Funded by the Alberta Spine Foundation; ClinicalTrials.gov number, NCT01053039.)

Patient Care: In an attempt to reduce the morbidity resulting from lumbar spine surgery, we have conducted a randomized, placebo-controlled trial demonstrating the safety and efficacy of intrathecal morphine for postoperative pain. We believe our findings will not only be of interest to those involved in the management of patients with degenerative disorders of the lumbar spine but also help guide future research in the field.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Discuss the potential benefit of an oblique intrathecal injection of 0.2 mg of morphine immediately prior to wound closure on postoperative pain following instrumented fusion of the lumbar spine; 2) Recognize that patients treated with 0.2 mg of intrathecal morphine are not at greater risk of respiratory depression; 3) Consider the use of intrathecal morphine as a means to significantly reduce intraoperative and postoperative opioid requirements.

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