OBJECTIVE: To examine the feasibility of a trial allocating different blood pressure (BP) intervention levels for treatment in extremely preterm infants. DESIGN: Three-arm open randomised controlled trial performed between February 2013 and April 2015. SETTING: Single tertiary level neonatal intensive care unit. PATIENTS: Infants born <29 weeks' gestation were eligible to participate, if parents consented and they did not have a major congenital malformation. INTERVENTIONS: Infants were randomised to different levels of mean arterial BP at which they received cardiovascular support: active (<30 mm Hg), moderate (<gestational age mm Hg) or permissive (signs of poor perfusion or <19 mm Hg). Once this threshold was breached, all were managed using the same treatment guideline. BP profiles were downloaded continuously; cardiac output and carotid blood flow were measured at 1 day and 3 days, and amplitude integrated EEG was recorded during the first week. Cranial ultrasound scans were reviewed blind to study allocation. MAIN OUTCOME MEASURE: Inotrope usage and achieved BP. RESULTS: Of 134 cases screened, 60 were enrolled, with mean gestation 25.8 weeks (SD 1.5) and birth weight 817 g (SD 190). Invasively measured BP on the first day and inotrope usage were highest in the active and lowest in the permissive arms. There were no differences in haemodynamic or EEG variables or in clinical complications. Predefined cranial ultrasound findings did not differ significantly; no infants in the active arm had parenchymal brain lesions. CONCLUSION: The BP threshold used to trigger treatment affects the achieved BP and inotrope usage, and it was possible to explore these effects using this study design. TRIAL REGISTRATION NUMBER: ISRCTN83507686
