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.
Kidney Support in Children using an Ultrafiltration Device: A Multicenter, Retrospective Study
CJASN, 2019, October; 14: 1-9, doi: 10.2215/CJN.03240319
Shina Menon, John Broderick, Raj Munshi, Lynn Dill, Bradley DePaoli, Sahar Fathallah-Shaykh, Donna Claes, Stuart L. Goldstein, and David J. Askenazi
Reviewed by Jennifer Jetton
What was the purpose of the study?
The purpose of this study is to report data from three centers on their experience with the use of the adapted Aquadex system to provide a range of kidney support therapies (CVVH, prolonged intermittent KRT, and slow continuous ultrafiltration) in children of all ages (not just infants). The authors present information on the characteristics of children supported with Aquadex as well as complications and short- and long-term outcomes.
What was the study design?
Multi-center, retrospective case series from three centers – Seattle Children’s Hospital (Seattle, WA), Children’s of Alabama (Birmingham, AL), and Cincinnati Children’s Hospital Medical Center (Cincinnati, OH).
What were the characteristics of the sample?
The study included data on 117 unique patients and 884 circuits used over 2338 days from January 2012 until March 2018. Patients were divided into 3 groups: < 10 kg, n = 72 [median age 19 (7,87) days, median baseline weight 3.2 (2.6, 4.3) kg], 10-20 kg, n = 13 [median age 26 (17,38) months, median baseline weight 12.3 (11.5, 13.7) kg], and > 20 kg, n = 34 [median age 190 (158, 258) months, median baseline weight 58.7 (37.1, 77) kg]. The series includes 6 patients < 2 kg. The smallest patient in the study was 1.4 kg.
What are the results/main learning points?
The adapted Aquadex CVVH system was used successfully in pediatric patients with a wide range of ages and weights. Specific care protocols and prescriptions varied by institution. Indication for KST varied by age group. For the < 10 kg, indications were AKI and electrolyte abnormalities (25%), volume overload (46%), AKI and volume overload (15%), and ESKD (with absolute or relative contraindication for PD – 14%). In the > 20 kg group, sites used the Aquadex system primarily for diuretic-resistant volume overload (91%). The authors report using Aquadex in several different clinical sites: PICU, NICU, acute care floors, and the outpatient chronic dialysis unit. Only 3% (23/884) of circuit initiations were complicated by instability requiring increase in cardiovascular support. Most (86%) were in the <10 kg group. Vascular-related complications occurred in 106 (15%) of treatments in the < 10 kg group. Infants < 4 kg still require a blood prime. Of note, the authors were not able to collect data on the number of catheter revisions that occurred.
As has been shown in other studies, the mortality rate in the < 10 kg group was higher than in the other groups. Only 32% (23/72) survived to hospital discharge (compared with 85% in the 10-20 kg group and 68% in the > 20 kg group) though 60% survived to discontinuation of KST. In patients weighing < 3kg, the survival rate was even lower (25%). For those who started KST in the first month of life, the 1-year survival was only 16%. The authors note that the smallest patients described in this series were complex with significant comorbidities including complex cardiac problems, prematurity, and low birth weight (e.g., patients who might otherwise have been too small or critically ill to be supported with existing dialysis tools).
What are the implications?
The adapted Aquadex system offers a potential KST option for all children with AKI, volume overload, and even ESKD in very small patients for whom PD is not an option. As exciting as this new therapy is, the smallest patients continue to be the most challenging to support and continue to demonstrate lower survival rates than older and bigger patients. In addition, this system is adapted and not specifically designed for the provision of CVVH. Thus, close monitoring is required at the bedside (as described above). We continue to wait for the availability of CARPEDIEM and NIDUS in the United States (as well as more experience with Aquadex) to see if we can make more favorable the benefit-risk equation when it comes to offering KST to small patients.
Editorial Note: For patients < 4 kg, the centers report using the following catheters: tunneled - Bard 6Fr x 50 cm (POWERLINE) and un-tunneled Bard 6Fr x 50 cm (POWERHOHN), Gambro 6Fr x 15 cm, Medcomp 7 Fr x 7 cm, and Medcomp 7Fr x 10 cm. Local resources and individual patient characteristics must be considered when choosing an appropriate catheter. The authors recommend discussing the benefits and challenges of using the adapted Aquadex system with an experienced center if you are interested in starting an Aquadex program in your own institution.