Lago 1998.

Study characteristics
Methods	Single‐centre randomised double‐blind controlled trial
Participants	55 preterm infants (26 to 34 weeks) requiring mechanical ventilation for hyaline membrane disease, with indwelling catheters Exclusion criteria: asphyxia (Apgar < 5 at 5 minutes); foetal drug exposure; sepsis; major congenital anomalies 2 infants died (1 in fentanyl group and 1 in control group) and were excluded from analysis
Interventions	Fentanyl group (n = 26): continuous infusion at 0.5 to 2 mcg/kg/hour adjusted to render the neonate sedated but arousable (according to the behavioural sedation score) Control group (n = 27): no intervention
Outcomes	Urine metanephrine:normetanephrine molar ratio concentration; behavioural sedation score (assessed every 2 hours during the study period); severity of hyaline membrane disease; need for surfactant replacement; evidence of clinically significant patent ductus arteriosus; days of ventilatory support and oxygen treatment; air leak; IVH; PVL; BPD; days to exclusive enteral feeding; days to reach birth weight; length of hospital stay
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Method of randomisation was not stated
Allocation concealment (selection bias)	Low risk	The use of sealed envelopes was reported (study author's communication)
Blinding of participants and personnel (performance bias)	High risk	Caregivers were not blinded
Blinding of outcome assessment (detection bias)	Unclear risk	Assessors were stated to be blinded to treatment, but blinding was unlikely
Incomplete outcome data (attrition bias)	High risk	2 patients died after enrolment and were excluded from statistical analysis
Selective reporting (reporting bias)	Unclear risk	Trial not registered; protocol not available
Other bias	Low risk	Study appears to be free of other sources of bias