Objective To assess, in newborn infants submitted to surgical procedures, the efficacy of two opioids—fentanyl and tramadol—regarding time to extubate, time to achieve 100 ml/kg of enteral feeding and pain in the first 72 h after surgery.

Design Controlled, blind, randomised clinical trial.

Setting Neonatal intensive care unit.

Patients 160 newborn infants up to 28 days of life requiring major or minor surgeries.

Interventions Patients were randomised to receive analgesia with fentanyl (1–2 μg/kg/h intravenously) or tramadol (0.1–0.2 mg/kg/h intravenously) in the first 72 h of the postoperative period, stratified by surgical size and by patient's gender.

Main outcome measures Pain assessed by validated neonatal scales (Crying, Requires oxygen, Increased vital signs, Expression and Sleepless Scale and the Neonatal Facial Coding System), time until extubation and time to reach 100 ml/kg enteral feeding. Statistical analysis included repeated measures analysis of variance adjusted for confounding variables and Kaplan–Meier curve adjusted by a Cox model of proportional risks.

Results Neonatal characteristics were (mean±SD) birth weight of 2924±702 g, gestational age of 37.6±2.2 weeks and age at surgery of 199±63 h. The main indication of surgery was gastrointestinal malformation (85 newborns; 53%). Neonates who received fentanyl or tramadol were similar regarding time until extubation, time to reach 100 ml/kg of enteral feeding and pain scores in the first 72 h after surgery.

Conclusion Tramadol was as effective as fentanyl for postoperative pain relief in neonates but does not appear to offer advantages over fentanyl regarding the duration of mechanical ventilation and time to reach full enteral feeding.

Trial registration NCT00713726