Neonatal fluid overload—ignorance is no longer bliss

JPediatric Nephrology volume 38, pages47–60 (2023). doi: 10.1007/s00467-022-05514-4

Weaver, L.J., Travers, C.P., Ambalavanan, N. et al. Neonatal fluid overload—ignorance is no longer bliss.

Reviewed by: Lucinda Weaver

Background:

The potentially detrimental impact of fluid overload continues to be extensively studied in adult and pediatric patients. Pediatric nephrologists and neonatologists have begun to examine associations between fluid overload and outcomes in the neonatal population.

Postnatally, infants experience natriuresis and diuresis as part of extrauterine adaptation. The degree of diuresis and natriuresis depends on a number of different prenatal and postnatal factors including, but not limited to, gestational age, birth weight, antenatal steroid usage, inherent kidney function, fluid administration, and postnatal humidity. Providers routinely monitor this process and adjust fluids to maintain fluid balance, avoid fluid overload, and prevent dehydration. However, neonates may have a variety of conditions that can predispose them to fluid imbalance and fluid overload.

What was the purpose of the review?

The article provides a comprehensive review of the impact of neonatal fluid overload and highlights areas needing further investigation. They outlined the definition, pathophysiology, and current understanding of neonatal fluid overload.  It also proposes a care bundle using the mnemonic “CAN U P LOTS”, which stands for Cause, Albumin, Nephrotoxicity, Ultrafiltration, Perfusion, Lasix Stress Test, Output, Total Fluid Intake, and Steroids, for the prevention and management of fluid overload.

What were the key areas of the review?

Infant, Newborn, Neonate, Fluid Overload, Fluid, Kidney, Acute Kidney Injury, Preterm, Extremely Low Birthweight, Diuretics, Mortality, Dialysis, Kidney Support Therapy

What were the key findings and/or contributions of the review?

Fluid balance is a metric (which can be negative or positive in relation to a previous point in time). Fluid balance is differentiated from fluid overload (which is a clinical entity that results from a positive fluid balance much like dehydration is a clinical entity that results from a negative fluid balance.  Currently, the most commonly used definition is the weight-based calculation: (cumulative weight change (%) = (daily weight (kg) − birth weight (kg))/birth weight (kg)). The in and out (cumulative fluid balance = total intake (mL) – total output (mL)) calculation may be more practical in certain circumstances. If a patient develops an unbalanced positive fluid state they are at risk of developing fluid overload. Fluid overload may be defined as excessive fluid accumulation resulting in edematous tissues and multiorgan dysfunction.

Could be: Fluid overload is a clinical entity, which is differentiated from the metric of fluid balance. Fluid overload results from a positive fluid balance much like dehydration results from a negative fluid balance. Weight-based calculations reflect a change from birthweight (cumulative weight change (%) = (daily weight (kg) − birth weight (kg))/birth weight (kg). The in and out (cumulative fluid balance = total intake (mL) – total output (mL)) calculation may be more practical in certain circumstances. If a patient develops an unbalanced positive fluid state they are at risk of developing fluid overload, defined as excessive fluid accumulation resulting in edematous tissues and multiorgan dysfunction.

The impact of fluid overload on all critically ill neonates was examined using The Assessment of Worldwide Acute Kidney injury Epidemiology in Neonates (AWAKEN) database. Selewski et al found that fluid overload was associated with prolonged mechanical ventilation on postnatal day 7 in both term and preterm infants. A Cochrane review including 5 randomized control trials and multiple retrospective analyses have shown associations with early liberal postnatal fluid administration in the extremely low birth weight population and adverse outcomes including prolonged mechanical ventilation, bronchopulmonary dysplasia (BPD), hemodynamically significant patent ductus arteriosus (PDA), necrotizing enterocolitis (NEC), and mortality. In particular, early liberal postnatal fluid administration increases the risk of NEC, but once an infant develops NEC they are at high risk of developing fluid overload. Other predisposing conditionsinclude sepsis, cardiac disease and the need for surgical management, congenital anomalies of the kidney and urogenital tract, and the need for extracorporeal membrane oxygenation (ECMO) support. Knowing the underlying pathophysiologic cause of the fluid overload will allow clinicians to implement targeted management and treatment strategies. For example, neonates, especially premature infants are at higher risk of developing acute kidney injury (AKI). Infants with AKI are at higher risk of developing an unbalanced fluid status. Close monitoring prevents the development and/or progression of AKI in this population to prevent the development of fluid overload.

The article discusses the use of kidney support therapy (KST) for critically ill infants with fluid overload including peritoneal dialysis, ultrafiltration, and hemofiltration, and discusses the particular challenges that arise due to the size of the patient population. Earlier initiation of KST may improve outcomes for patients at risk of developing fluid overload, as a more positive fluid balance at the time of KST initiation has been associated with a higher risk of mortality and other adverse outcomes in critically ill infants.

What are the implications?

Knowledge of the importance of monitoring and managing fluid overload appropriately is imperative to providing appropriate patient care. Fluid overload in the neonatal population can be difficult to navigate as they have different disease pathophysiologies, and neonatal physiology continuously evolves throughout the course of the infant’s life. The mnemonic “CAN U P LOTS” is a tool that can be used to evaluate and treat neonates with fluid overload.

Limitations?

Ultimately, while the use of the treatment bundle described may be helpful in clinical practice, further evidence is urgently needed.