The use of intrathecal morphine for analgesia after posterolateral lumbar fusion: a prospective, double-blind, randomized study.

STUDY DESIGN: A prospective, randomized, double-blind, placebo-controlled study was undertaken to evaluate the efficacy and safety of intrathecal morphine for postoperative analgesia after posterolateral lumbar fusion.

OBJECTIVES: To compare the early postoperative analgesia in patients who receive a single dose of intrathecal morphine intraoperatively with that of patients using a patient-controlled analgesia pump only.

SUMMARY OF BACKGROUND INFORMATION: Although intrathecal morphine is used as an analgesic in a variety of medical and surgical conditions, very little has been published on its use after posterior lumbar spine surgery. Because the thecal sac is readily available during these procedures, the addition of a single injection of morphine before wound closure can be done with technical ease. If its efficacy and safety can be verified, then it could serve as a useful adjuvant to the postoperative analgesia regimen.

METHODS: Sixty-eight consecutive patients undergoing posterolateral lumbar fusion were randomly assigned to two groups. The experimental group was injected intrathecally with morphine 30 minutes before wound closure, and the control group was similarly injected with a placebo of normal saline solution. All patients were connected to an on-demand patient-controlled analgesia pump to provide any additional necessary analgesia. Their use of the patient-controlled analgesia pump was tabulated by counting the number of demands and the actual amount of morphine delivered. Additionally, a visual analog scale was used to assess pain levels at pre-established regular intervals.

RESULTS: The visual analog scale measurements were significantly lower for the intrathecal morphine group initially, but they surpassed those of the control group after 24 hours. Likewise, the number of patient-controlled analgesia pump demands and the amount of narcotic delivered initially were significantly lower in the experimental patients, but again reversed after the first postoperative day. The late rebound in pain and patient-controlled analgesia pump use did not reach statistical significance. There were no significant complications related to the analgesia.

CONCLUSIONS: Intrathecal morphine can be safe and efficacious as an early postoperative analgesic after lumbar fusion when respiratory monitoring is used.