AKI in hospitalized children: epidemiology and clinical associations in a national cohort

Abstract

Background and objectives: Although AKI is common among hospitalized children, comprehensive epidemiologic data are lacking. This study characterizes pediatric AKI across the United States and identifies AKI risk factors using high-content/high-throughput analytic techniques.

Design, setting, participants, & measurements: For the cross-sectional analysis of the 2009 Kids Inpatient Database, AKI events were identified using International Classification of Diseases, Ninth Revision, Clinical Modification codes. Demographics, incident rates, and outcome data were analyzed and reported for the entire AKI cohort as well as AKI subsets. Statistical learning methods were applied to the highly imbalanced dataset to derive AKI-related risk factors.

Results: Of 2,644,263 children, 10,322 children developed AKI (3.9/1000 admissions). Although 19% of the AKI cohort was ≤ 1 month old, the highest incidence was seen in children 15-18 years old (6.6/1000 admissions); 49% of the AKI cohort was white, but AKI incidence was higher among African Americans (4.5 versus 3.8/1000 admissions). In-hospital mortality among patients with AKI was 15.3% but higher among children ≤ 1 month old (31.3% versus 10.1%, P<0.001) and children requiring critical care (32.8% versus 9.4%, P<0.001) or dialysis (27.1% versus 14.2%, P<0.001). Shock (odds ratio, 2.15; 95% confidence interval, 1.95 to 2.36), septicemia (odds ratio, 1.37; 95% confidence interval, 1.32 to 1.43), intubation/mechanical ventilation (odds ratio, 1.2; 95% confidence interval, 1.16 to 1.25), circulatory disease (odds ratio, 1.47; 95% confidence interval, 1.32 to 1.65), cardiac congenital anomalies (odds ratio, 1.2; 95% confidence interval, 1.13 to 1.23), and extracorporeal support (odds ratio, 2.58; 95% confidence interval, 2.04 to 3.26) were associated with AKI.

Conclusions: AKI occurs in 3.9/1000 at-risk US pediatric hospitalizations. Mortality is highest among neonates and children requiring critical care or dialysis. Identified risk factors suggest that AKI occurs in association with systemic/multiorgan disease more commonly than primary renal disease.

Figure 1.

Cohort optimization. Patients >18 years old were excluded to create a cohort representative of pediatric disease. Uncomplicated births (by Kids’ Inpatient Database [KID] definition) and patients with ESRD (receiving chronic dialysis) are not at risk for AKI. Creatinine elevations in renal transplant recipients are likely to represent a diagnosis other than AKI (allograft dysfunction).

Figure 2.

AKI patient demographics and incident rates. AKI analysis by (A) age and (B) race. Each percent figure represents the percentage of the entire AKI cohort. Additionally, AKI incidence (AKI events per 1000 hospitalizations) is shown from lowest to highest.

Figure 3.

AKI hospital demographics and incident rates. AKI analysis by (A) hospital size and (B) hospital type. Each percent figure represents the percentage of the entire AKI cohort. Additionally, AKI incidence (AKI events per 1000 hospitalizations) is shown from lowest to highest.

Figure 4.

Outcomes. Mortality rates (%) and length of stay (median days) are shown for patients with and without AKI, AKI patients >1 and ≤1 month of age, AKI patients who required and did not require dialysis, and AKI patients who received and did not receive critical care. ICU, intensive care unit; LOS, length of stay.