Neonates and infants with acute kidney injury (AKI) and congenital kidney failure (CKF) who require extracorporeal kidney replacement therapy (KRT) have long been managed with devices that were designed and made with adult patients in mind. For years, pediatricians have improvised with adult hand-me-downs and jury-rigged adult-sized devices for use in children. The same has been true for KRT also.

In 2007, the Pediatric Medical Device Safety and Improvement Act (PMDSIA) was passed to encourage device innovation for medical conditions that impact pediatric populations. Despite that, and other initiatives by the Food and Drug Administration (FDA) to incentivize pediatric device development, progress has been stagnant.

Copyright: Tomatheart / Shutterstock

Most of us have initiated CKRT on infants using a Prismaflex with a big sticker on it that said, “WARNING: Only intended for patients weighing 20 kilograms or more”. We have all had to explain to worried parents that despite the warning, we still recommended therapy with that machine! And then, the team of nephrologists and intensivists would wait with bated breaths, and with intravenous calcium, vasoactive medications, and bicarbonate to prevent the infant from ‘crashing’ at CKRT initiation. Until recently, the smallest CKRT filter available in the United States had an extracorporeal circuit volume (ECV) of 97 mL. For a term neonate weighing 2.5 kg, with a total blood volume (TBV) of 200 mL, the ECV/TBV ratio with this filter is almost 50%. CKRT initiation with such a filter in this baby would always require blood prime. Additionally, the high ECV/TBV ratio and the volume of blood prime significantly increase the risk of hemodynamic instability at circuit initiation.

CKRT machines designed for adults not only have larger filters, but also require higher blood flows, and hence, larger dialysis catheters. The diameter of the internal jugular vein in neonates and infants weighing between 1.4-4.5 kg may range between 1.5-4.8 mm. Thus, CKRT with conventional devices may not be a feasible option for some of the neonates we see in the NICU, who are too small to have a 7 or 8 French double-lumen dialysis catheter inserted.

However, it’s a new day!

The last 3-5 years have seen remarkable progress in the field of novel devices for neonatal nephrology! It started with Dr David Askenazi adapting Aquadex to provide continuous veno-venous hemofiltration in neonates. Since then, we have had FDA approval for CARPEDIEM^TM and HF-20. CARPEDIEM was designed by Dr Claudio Ronco and his team with the safety of small infants and neonates in mind, with smaller filters, lower blood flows, and more accurate ultrafiltration. In addition to  all the usual advantages of dialysis with an age-appropriate device, the lower blood flows allow one to use smaller catheters. Although smaller hemodialysis catheters are not yet available in the United States, centers have used 6 French double-lumen PowerPICC or 2 single-lumen PowerPICCs to provide CKRT with both CARPEDIEM and Aquadex.

And there are likely more devices to come! In the United Kingdom, the Newcastle Infant Dialysis Ultrafiltration System (NIDUS) has been studied in a single center, and is now undergoing multicenter assessments. NIDUS has an ECV of less than 10 mL and works with a single-lumen access.

If this isn’t exciting, then what is?

I look forward to a future where an array of options may be available for the nephrologist providing KRT to a neonate or infant who needs it. The baby may require continuous therapy with a device that has accurate ultrafiltration and good filter life when they are acutely ill, then transition to prolonged intermittent therapy with a device that does not need daily blood priming, waiting for the PD catheter to heal, so they can go home on chronic PD.

Children are not small adults! It is very satisfying to see the field move from adapted devices to pediatric-specific ones. In an ideal world, one will have neonates and infants with healthy kidneys. However, until that happens, I am glad we have various pediatric-focused options for the children who need these therapies!