There is an unmet need for devices designed specifically for the provision of continuous renal replacement therapy to small patients with acute kidney injury and fluid overload. In the inaugural issue of the NKC Article of the Month series, we review two articles reporting experience with the novel use of a machine currently available in the United States and FDA-approved for ultrafiltration in adults with congestive heart failure. The first article reports a single center’s initial experience using the Aquadex FlexFlow System (Aquadex; CHF Solutions Inc., Eden Prairie, MN) adapted to provide continuous veno-venous hemofiltration (CVVH) for infants and small children. The second article summarizes findings from a larger multi-center study of the use of this device in infants and older children in need of kidney replacement therapy. 


Smaller circuits for smaller patients: Improving renal support therapy with Aquadex

Pediatric Nephrology, 2016, May; 31(5):853-860, doi: 10.1007/s00467-015-3259-3

David Askenazi, Daryl Ingram, Suzanne White, Monica Cramer, Santiago Borasino, Carl Coghill, Lynn Dill, Frank Tenney, Dan Feig, and Sahar Fathallah-Shaykh

Reviewed by Arwa Nada

What was the purpose of the study?
The authors hypothesized that using a machine with a small extravascular volume (ECV) can improve the care and safety of children who need kidney support therapy by minimizing complications and hemodynamic instability typically seen at CRRT initiation because of the use of proportionally large catheters and circuit volumes.

What was the study design?
Retrospective case series from a single center.

What were the characteristics of the sample?
The report included 12 small children at Children’s of Alabama (Birmingham, Al) who received continuous veno-venous hemofiltration (CVVH) using Aquadex adapted for KRT. The median age of patients at initiation of therapy was 30 days (4 days - 4 years; IQR = 13, 38 days). The median weight at initiation was 3.4 kg (2.7 kg - 12.4 kg; IQR = 3.0, 4.3 kg).

What are the results/main learning points?
The adapted Aquadex CVVH system was used successfully in neonates as small as 2.7 Kg without the need for intensive cardiovascular, respiratory, or blood product support.

Aquadex has a 33 ml ECV when using the 500-filter set with hematocrit monitor. A 0.12 m2 polysulfone filter is available. In comparison, the Newcastle Infant Dialysis Ultrafiltration System (NIDUS) has an ECV of 6.5 mL for filters of 0.045 m2 and provides diffusive solute clearance. The Cardiac and Renal Pediatric Dialysis Emergency (CARPEDIEM™) system has available circuits of 27, 34 and 45 mL for filters of 0.075, 0.15 and 0.25 m2 and provides convective clearance. Both systems have been used in Europe but are yet to be approved in USA.

What are the implications?
Dialyzing neonates is challenging due to lack of availability of FDA-approved, small volume circuits designed specifically for KST. Though this is a small case series, the experience reported demonstrates the potential for the adapted Aquadex CVVH system to deliver therapy safely to our smallest patients and is worthy of further study. In addition, this therapy could be a potential solution for infants in need of KST for whom peritoneal dialysis is not an option.

One primary limitation is that the heparin infusion and replacement fluids must be given through separate flow regulators external to the device and are not directly integrated with the Aquadex machine. Thus, extra vigilance is required at the bedside. The development of CRRT machines with a small ECV suitable for infants continues to be of utmost importance for the management of critically ill neonates with AKI.