The development of standardized acute kidney injury (AKI) definitions has allowed for a better understanding of AKI, but long term data on patients following the pediatric critical care setting are sparse. A recent article published in the American Journal of Kidney Diseases is the largest pediatric AKI prospective cohort study ever to follow survivors of severe AKI. Corresponding author Dr. Cherry Mammen (CM) from the Department of Pediatrics, Division of Nephrology, University of British Columbia, Canada, spoke with Dr. Sidharth Sethi (eAJKD), eAJKD advisory board member, on this topic.

eAJKD: Can you give us some background about the study?

CM: The objectives of this study were to assess the long-term kidney outcomes of children surviving episodes of AKI in the pediatric ICU setting. We wanted to determine three major objectives: (1) the incidence of CKD in children 1-3 years after an episode of AKI at a tertiary-care pediatric ICU, (2) the proportion of patients at risk of CKD, and (3) the characteristics upon ICU admission of those with and without future CKD.

eAJKD: What was the definition of “at-risk for CKD” patients?

CM: The “at-risk for CKD” definition is not the true KDOQI (Kidney Disease Outcomes Quality Initiative) definition of CKD, but outcomes that we felt were important in this young population. In those older than 2 years, abnormal kidney function was defined as a glomerular filtration rate (GFR) <60 mL/min/1.73 m² or the presence of persistent albuminuria. We defined those “at-risk for CKD” as having a mildly decreased GFR of 60-90 mL/min/1.73 m², persistent hypertension, and/or hyperfiltration with a GFR >150 mL/min/1.73m².

eAJKD: The Acute Kidney Injury Network (AKIN) criteria were used for newborns in your study. Is that appropriate?

CM: Newborns comprised 25% of our studied cohort. No one really knows the best way to evaluate and define AKI in this age group. Similarly, for those younger than 2 years, GFR criteria were not available to define CKD or those at-risk for CKD because thresholds have yet to be developed in this age group. AKIN was useful in helping us better classify this group. Overall, we felt justified using the AKIN criteria in neonates as several recent neonatal AKI studies have utilized the AKIN definition successfully.

eAJKD: What is the incidence of AKI in the pediatric ICU?

CM: The primary intent of the study was to evaluate the incidence of CKD. Hence, we cannot give you an incidence of AKI in the pediatric ICU populations. However, this study did lead to further work from our group.  As a large proportion of the cohort was neonates undergoing cardiac surgery, we were able to look at the incidence of AKI in neonates undergoing cardiac surgery for congenital heart disease. Using the AKIN criteria, the incidence of AKI was almost 50% in that group.

eAJKD: And out of these neonates, how many require renal replacement therapy?

CM: We found that 33% of the babies fell into the definition of Stage III AKI. Out of those third, 10% required renal replacement therapy.

eAJKD: Can you comment on the incidence of CKD in the various AKIN groups?

CM: The incidence of CKD (KDOQI definition) in our population of 126 patients that were seen in follow-up was 10%. There were no major differences seen in terms of the numbers of CKD patients in the various AKIN criteria. When we looked at albumin-to-creatinine ratios in the urine, the median albumin-to-creatinine ratio for this population upon follow-up increased as AKI severity increased. In addition, when we looked at the risk factors for CKD in terms of AKI severity, the need for dialysis was one factor that was highly significant.

eAJKD: Based on the current study, what would be your take-home message for nephrologists reading this interview?

CM: The major message is that the standardized AKI definitions should be used in ICU settings. With the development of validated scores like AKIN or RIFLE, we are able to identify patients that may be at risk for long-term renal sequelae. For example, in this study we identified 47 patients with CKD upon follow-up. We feel that the AKIN criteria should be used by all nephrologists and intensivists to identify patients who are at risk of developing CKD the future. The last point is that all patients who develop AKI in the ICU setting, regardless of etiology or severity, should be followed long term for the development of CKD with at least annual urinalysis and blood pressure checks.

eAJKD: What are your future plans on studying this population?

CM: This study was useful as it identified specific subpopulations that may be at risk for CKD. For example, approximately half of our cohort were children with congenital heart disease. Our center is now working on prospective studies looking at the AKIN criteria in these babies while comparing the urine output and serum creatinine criteria head to head. We are also analyzing AKI biomarkers and their correlation to the serum creatinine and urine output AKIN criteria to determine which is a better measure of AKI in this young susceptible population.

In addition, we found other populations that have not been previously studied; for example, patients undergoing scoliosis surgeries. This is a group that really has not been defined as a high-risk population, but we identified 10 patients that developed Stage II and Stage III AKI. Studying that group may be helpful for predicting future kidney disease.

To view the article abstract or full-text (subscription required), please visit AJKD.org; see also the freely available editorial.