Intrathecal morphine for postoperative analgesia in patients with idiopathic scoliosis undergoing posterior spinal fusion

Abstract

Study Design.: A retrospective study of postoperative pain management with intrathecal morphine. Objective.: Identify the dosing regimen of intrathecal morphine that safely and effectively provides postoperative analgesia with minimal complications in patients with idiopathic scoliosis undergoing posterior spinal fusion (PSF) and segmental spinal instrumentation (SSI). Summary of background data.: Postoperative pain after surgery for idiopathic scoliosis is a concern. Intrathecal morphine has been used to decrease pain. However, the most appropriate dose has not been determined. Methods.: We retrospectively analyzed 407 consecutive patients with idiopathic scoliosis who underwent PSF and SSI at our institution from 1992 through 2006. Patients were divided into 3 groups based on the intrathecal morphine dose: no dose (n = 68); moderate dose of 9 to 19 μg/kg, mean 14 μg/kg (n = 293); and high dose of 20 μg/kg or greater, mean 24 μg/kg (n = 46). Data included demographics, Wong-Baker visual analog scale postoperative pain scores, postoperative intravenous morphine requirements, time to first rescue dose of intravenous morphine, and postoperative complications of pruritis, nausea/vomiting, respiratory depression, and pediatric intensive care unit (PICU) admission. Results.: The demographics of the 3 study groups showed no statistical differences. The mean Wong-Baker visual analog scale pain score in the post anesthesia care unit was 5.2, 0.5, and 0.2, and the mean time to first morphine rescue was 6.6, 16.7, and 22.9 hours, respectively. In the first 48 postoperative hours, respiratory depression occurred in 1 (1.5%), 8 (2.7%), and 7 (15.2%) patients, whereas PICU admission occurred in 0 (0%), 6 (2%), and 8 (17.4%) patients, respectively. The majority of PICU admissions were the result of respiratory depression. Frequency of pruritis and nausea/vomiting was similar in all 3 groups. Conclusion.: Intrathecal morphine in the moderate dose range of 9 to 19 μg/kg (mean 14 μg/kg), provides safe and effective postoperative analgesia in the immediate postoperative period for patients with idiopathic scoliosis undergoing PSF and SSI. Higher doses did not result in significantly better analgesia and had a greater frequency of respiratory depression requiring PICU admission. © 2008, Lippincott Williams & Wilkins.