A retrospective comparison of intrathecal morphine and epidural hydromorphone for analgesia following posterior spinal fusion in adolescents with idiopathic scoliosis.

BACKGROUND: Posterior spinal fusion to correct idiopathic scoliosis is associated with severe postoperative pain. Intrathecal morphine is commonly used for analgesia after adolescent posterior spinal fusion; however, anticipating and managing the increase in pain scores after resolution of analgesic effect of intrathecal morphine analgesia is challenging. In 2014, we developed a clinical protocol detailing both the administration of intrathecal morphine intraoperatively and the transition to routine, scheduled oral analgesics at 18 h postoperatively. The goal of our study was to examine the efficacy of our intrathecal morphine protocol vs epidural hydromorphone for postoperative analgesia after posterior spinal fusion.

METHODS: Following IRB approval, we retrospectively identified developmentally intact children of ages 10-20 years in our electronic database with a diagnosis of idiopathic scoliosis who had undergone elective posterior spinal fusion surgery from June 2014 to April 2015. For the intrathecal morphine group, intrathecal morphine was administered in a dose of 12 μg·kg-1 (max 1000 μg) prior to incision. Postoperatively, all children in the intrathecal morphine group had an order to receive oral oxycodone (0.1 mg·kg-1 , max 5 mg) starting at 18 h postintrathecal morphine injection. For the epidural hydromorphone group, catheters were placed by the surgeon and bolused with 5 μg·kg-1 hydromorphone (max 200 μg) and 1 μg·kg-1 fentanyl (max 50 μg), followed by a continuous infusion of 40-60 μg·h-1 , and patient-controlled bolus doses of 5 μg with a lockout interval of 30 min. All patients in both groups had postoperative orders for acetaminophen, diazepam, and ketorolac.

RESULTS: During the study time period, 20 patients received intrathecal morphine and were successfully matched with 20 patients who received epidural hydromorphone. All patients in the intrathecal morphine group were transitioned to oral analgesics on the first postoperative day, without need for intravenous opioids after discharge from the postanesthesia care unit. Compared to the epidural hydromorphone group, the intrathecal morphine group reported lower pain scores in the postanesthesia care unit (difference in means -4.26 [95% CI -6.56, -1.96], P = 0.001) and first 8 h after surgery (difference in means -1.88 [95% CI -3.84, 0.082, P = 0.060) and higher pain scores on the 2nd postoperative day (difference in means 1.60 [95% CI 0.10, 3.10], P = 0.037). The documented time to ambulation and time of Foley catheter removal were statistically earlier in the intrathecal morphine group, and the hospital length of stay was significantly shorter (3.0 ± 0.5 days vs 3.5 ± 0.7 days; P = 0.03). Adverse events did not significantly differ between the groups.

CONCLUSION: The efficacy of intraoperative intrathecal morphine for postoperative analgesia in the posterior spinal fusion patient population has been shown previously; however, the pain and analgesic trajectory, including transition to other analgesics, has not previously been studied. Our findings suggest that for many patients, use of intrathecal morphine in addition to routine administration of nonopioid medications facilitates direct transition to oral analgesics in the early postoperative period and earlier routine ambulation and discharge of posterior spinal fusion patients.