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 microg/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 microg/kg morphine, and 5 microg/kg morphine groups, respectively. Pain scores at rest were significantly lower over the whole study period after 2 and 5 microg/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 microg/kg seem to have similar effectiveness and side-effect profiles, whereas a reduction of intraoperative bleeding was observed in patients who received 5 microg/kg but not 2 microg/kg intrathecal morphine.