UPMC Children’s Newborn Medicine and Nephrology Divisions Collaborate to Develop Aquadex^® Program to Support Kidney Function in Critically Ill Newborns

Kidney failure and fluid overload are frequent complications in extremely premature and critically ill newborns. Many of these infants have structurally immature or injured kidneys that struggle with basic physiologic processes, let alone the added stresses of prolonged intensive care unit stays.

The introduction of the Aquadex^® system at UPMC Children’s Hospital of Pittsburgh has created a treatment pathway for a group of infants who historically had few options when kidney failure and fluid overload became life-threatening. Although Aquadex was designed as a compact ultrafiltration system for adults with heart failure to manage fluid overload, its small circuit has made it adaptable to premature and critically ill neonates whose size can make conventional dialysis difficult to impossible.

“Before we had access to this type of system, some premature or very premature infants with underdeveloped kidneys or severe kidney disease did not have a viable bridge to dialysis or transplant. If they could not grow to a size where those therapies became feasible, our ability to support them was limited,” says Abeer Azzuqa, MD, clinical director of the Neonatal Intensive Care Unit at UPMC Children’s and professor of pediatrics in the Division of Newborn Medicine at the University of Pittsburgh School of Medicine.

Why Size Limits Conventional Kidney Replacement Therapy in Neonates

In the smallest infants, kidney replacement therapy is limited not by the severity of kidney failure or insufficiency but by extracorporeal blood volume. A 900-gram neonate has a total blood volume of about 70 to 80 milliliters. The smallest traditional pediatric continuous renal replacement therapy circuits need 60 milliliters to fill the tubing and filter. This means that a large percentage of an infant’s circulation is outside the body at all times. This is not a natural or optimal state.

Any interruption in flow from clots, system alarms, or catheter issues can destabilize blood pressure, oxygen delivery, and metabolic control. Blood priming of the circuit becomes necessary, increasing transfusion exposure and immune sensitization in infants who may need kidney transplantation in the future.

“What stops us from using conventional dialysis in many of these babies is not how bad their kidneys are. It is how much blood you have to take out of their body just to run the circuit,” says Katherine Kurzinski, MD, assistant professor of pediatrics in the Division of Pediatric Nephrology and medical director of the Pediatric Dialysis Program at UPMC Children’s.

Why Aquadex Changes the Size Constraint

Aquadex was originally developed for adult patients who needed controlled ultrafiltration outside of a dialysis unit. Its defining feature is a very low extracorporeal blood volume derived from compact filters and short tubing paths. For neonates, these properties become an advantage.

The smaller circuit reduces the amount of blood that must be outside the infant’s body at any moment. In some neonates, it eliminates the need for blood priming, and even when priming is needed the physiologic impact is lower than with conventional renal therapy systems.

“What makes the system usable in this population is not just its gentler nature, but that it’s small,” Dr. Kurzinski says. “That is what allows the baby to tolerate being connected.”

UPMC Children’s initially adopted the system in the Pediatric Intensive Care Unit for small critically ill children who needed fluid removal. As experience accumulated, the nephrology and neonatal teams recognized that the same low-volume design could be applied to extremely premature infants.

How Aquadex Was Adapted for Neonatal Kidney Support

In its standard configuration, the system removes fluid but does not provide metabolic clearance. To make it useful for neonatal kidney failure, the nephrology team adapted a convective strategy that allows solute removal alongside ultrafiltration.

Sterile replacement fluid is infused into the circuit and removed through ultrafiltration. As plasma water crosses the filter, dissolved solutes are carried with it. By independently adjusting replacement and removal rates, the clinical team can control both fluid balance and metabolic clearance.

“That approach lets us treat both sides of kidney failure,” Dr. Kurzinski says. “We can manage fluid overload when ventilation or cardiac function is the problem, and we can provide metabolic support when electrolyte or acid–base disturbances manifest.”

Which Infants Are Candidates for Aquadex Therapy

Aquadex is used in neonates whose size, kidney function, and degree of fluid or metabolic derangement cannot be managed with medication alone.

One group includes infants with congenital or chronic kidney disease, including renal dysplasia or bilateral hypoplastic kidneys. These babies are often too small for peritoneal dialysis catheters or standard dialysis circuits in the early weeks or months of life. The system allows them to remain physiologically stable while they grow.

“For these infants, the objective is to buy time so they can reach a size where peritoneal dialysis or transplant becomes an option,” Dr. Kurzinski says.

A second group of candidates includes premature and critically ill infants with acute kidney injury due to sepsis, necrotizing enterocolitis, respiratory failure, congenital heart disease, and other issues. In these patients, kidney dysfunction is often accompanied by capillary leak and fluid overload that worsens ventilation and hemodynamic stability. Some will recover kidney function if supported through the acute inflammatory phase.

“Our goal is either recovery or transition to a more durable therapy,” Dr. Azzuqa says. “Aquadex gives us the physiologic control needed to reach that point.”

How Aquadex Therapy Is Managed in Practice at UPMC Children’s

The risk profile of Aquadex in neonates is driven by its low circuit volume. Because less blood is outside the body, circuit interruptions carry less hemodynamic and metabolic penalty. Reduced reliance on blood priming also limits transfusion exposure and immune sensitization.

“Some of these infants can be connected without a blood prime, which substantially reduces transfusion exposure,” Dr. Kurzinski says. “That has important downstream consequences with respect to future care needs.”

However, Aquadex introduces technical challenges of its own. Neonatal catheters are small and sensitive to position. Premature infants move unpredictably, triggering pressure changes and alarms. Anticoagulation must be balanced carefully against bleeding risk, and clotting is always a concern.

“This is not a passive therapy,” Dr. Azzuqa says. “Fluid balance, electrolytes, and acid–base status has to be reassessed continuously, with nephrology guiding those adjustments. We have adapted a system designed for adults to work well in some of the smallest babies, but with that comes challenges we have to deal with.”

Running Aquadex in neonates is an active, real-time clinical process. Premature infants have almost no margin for error in fluid balance. Continuous infusions of medications, nutrition, blood products, and replacement fluids must all be incorporated into ultrafiltration targets.

“Every milliliter of blood and fluid matters in these patients. The nursing staff calculates intake and output hour by hour, and the Aquadex settings are adjusted in real time based on what the baby is actually receiving and tolerating,” Dr. Kurzinski says. “They do a phenomenal job managing this very labor intensive and complex therapy.”

The system’s sensitivity to pressure changes means alarms are frequent, and the nursing team must constantly distinguish between true circuit problems and infant movement. When clotting occurs, circuits must be changed with careful blood return to minimize volume loss.

“This is not a set-and-forget therapy. It is a shared clinical process between neonatology, nephrology, and specially trained nurses, one that has to be adapted on the fly as a patient’s clinical status changes” Dr. Azzuqa says.