The Goldilocks Principle in Neonatal Fluids: Finding the Just-Right Balance

The impact of disrupted fluid balance on outcomes in critically unwell children and adults is well described. Recent literature in neonates has demonstrated that both fluid overload and excessive postnatal fluid losses are associated with increased morbidity and mortality. However, neonates present unique challenges in measuring fluid balance as well as defining, preventing and treating fluid overload due to developmental changes in renal physiology, high trans-epidermal losses, nutritional requirements and limitations in available renal replacement therapies. In the neonatal intensive care unit, significant variations exist in renal physiology and expected fluid shifts between neonates of differing gestational and chronological ages, as well as in the neonate's underlying co-morbidities. As such, approaches to fluid balance should be individualised to each patient. Recognition of fluid balance as a vital sign, with implications as relevant as a patient's cardiorespiratory status, provides an important opportunity to improve outcomes. In this scoping review we discuss neonatal renal and fluid balance physiology, and present contemporary best practice strategies for measuring fluid balance. We explore the currently available prevention and treatment options for fluid overload in Australia and New Zealand as well as technological advances in neonatally-adapted haemodialysis (HD) and continuous renal replacement therapies emerging internationally.