Efficacy of continuous versus intermittent morphine administration after major surgery in 0-3-year-old infants; a double-blind randomized controlled trial

A randomized double-blind clinical trial compared the efficacy of 10 mug/kg/h morphine continuous intravenous infusion (CM) with that of 30 mug/kg morphine (IM) every 3 h after major abdominal or thoracic surgery, in 181 infants aged 0-3 years. Efficacy was assessed by the caregiving nurses with the COMFORT 'behavior' and a visual analogue scale (VAS) for pain, every 3 It in the first 24 h after surgery. Random regression modeling was used to simultaneously estimate the effect of randomized group assignment, actual morphine dose (protocol dosage plus extra morphine when required). age category, surgical stress, and the time-varying covariate mechanical ventilation on COMFORT 'behavior' and the observational VAS rated pain, respectively. Overall. no statistical differences were found between CM and IM morphine administration in reducing postoperative pain. A significant interaction effect of condition with age category showed that the CM assignment was favorable for the oldest age category (1-3 years old). The greatest differences in pain response and actual morphine dose were between neonates and infants aged 1-6 months, with lower pain response in neonates who were on average satisfied with the protocol dosage of 10 mug/kg/h. Surgical stress and mechanical ventilation were not related to postoperative pain or morphine doses, leaving the interindividual differences in pain response and morphine requirement largely unexplained. (C) 2002 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved.