Restricted Versus Liberal Fluid Intake for Prevention of Bronchopulmonary Dysplasia - RELIEF Trial. A Cluster-randomised Multiple Period Cross-over Trial.

Complications of preterm birth remain the leading cause of death in children under five years of age worldwide, accounting for approximately one million deaths annually. Among the survivors, bronchopulmonary dysplasia (BPD) is the most common severe complication. BPD is a chronic lung disease characterized by prolonged need for respiratory support and oxygen therapy, poor postnatal growth, and long-term impairments in lung function and neurodevelopment.

Despite advancements in neonatal care, BPD is the most common chronic lung disease in infancy and associated with increased mortality, repeated hospitalisation throughout childhood, impaired lung function up into adulthood, and long-term neurodevelopmental impairment. The incidence of BPD has remained stable over the past 15 years. This is likely due to the improved survival of extremely preterm infants, who are at the highest risk for BPD.

A key feature of evolving BPD is the accumulation of interstitial pulmonary edema, which reduces lung compliance and increases the need for respiratory support, thereby perpetuating a cycle of lung damage.

Currently, diuretics are sometimes used to manage pulmonary edema in preterm infants. While they can improve lung function in the short term, they come with potential risks including bone demineralization, nephrotoxicity, electrolyte imbalances, and impaired growth.

As a potentially safer alternative, fluid restriction is sometimes used to prevent or manage pulmonary edema. It is hypothesized to improve lung mechanics and reduce the need for respiratory support, without the adverse effects associated with medications. However, there is no robust evidence on optimal fluid targets in these patients.