Analgesic effect of low-dose intrathecal morphine after spinal fusion in children

Background: This study was designed to assess the postoperative analgesic effect of low-dose intrathecal morphine after scoliosis surgery in children. Methods: Thirty children, 9-19 yr of age, scheduled for spinal fusion, were randomly allocated into three groups to receive a single dose of 0 (saline injection), 2, or 5 mug/kg intrathecal morphine. After surgery, a patient-controlled analgesia device (PCA) provided free access to additional intravenous morphine. Children were monitored for 24 h in the postanesthesia care unit. Results: The three groups were similar for age, weight, duration of surgery, and time to extubation. The time to first PCA demand was dose-dependently delayed by intrathecal morphine. The first 24 h of PCA morphine consumption was 49 +/- 17, 19 +/- 10, and 12 +/- 12 mg (mean +/- SD) in the saline, 2 mug/kg morphine, and 5 mug/kg morphine groups, respectively. Pain scores at rest were significantly lower over the whole study period after 2 and 5 mug/kg intrathecal morphine than after saline, but there was no difference between intrathecal doses. Pain scores while coughing and the Incidence of side effects were similar in the three groups. Conclusions: These data demonstrate that low-dose intrathecal morphine supplemented by PCA morphine provides better analgesia than PCA morphine alone after spinal fusion in children, The doses of 2 and 5 mug/kg seem to have similar effectiveness and side-effect profiles, whereas a reduction of intra-operative bleeding was observed in patients who received 5 mug/kg but not 2 mug/kg intrathecal morphine.