Epidemiology of Acute Kidney Injury in Critically Ill Children and Young Adults

Abstract

Background: The epidemiologic characteristics of children and young adults with acute kidney injury have been described in single-center and retrospective studies. We conducted a multinational, prospective study involving patients admitted to pediatric intensive care units to define the incremental risk of death and complications associated with severe acute kidney injury.

Methods: We used the Kidney Disease: Improving Global Outcomes criteria to define acute kidney injury. Severe acute kidney injury was defined as stage 2 or 3 acute kidney injury (plasma creatinine level ≥2 times the baseline level or urine output <0.5 ml per kilogram of body weight per hour for ≥12 hours) and was assessed for the first 7 days of intensive care. All patients 3 months to 25 years of age who were admitted to 1 of 32 participating units were screened during 3 consecutive months. The primary outcome was 28-day mortality.

Results: A total of 4683 patients were evaluated; acute kidney injury developed in 1261 patients (26.9%; 95% confidence interval [CI], 25.6 to 28.2), and severe acute kidney injury developed in 543 patients (11.6%; 95% CI, 10.7 to 12.5). Severe acute kidney injury conferred an increased risk of death by day 28 after adjustment for 16 covariates (adjusted odds ratio, 1.77; 95% CI, 1.17 to 2.68); death occurred in 60 of the 543 patients (11.0%) with severe acute kidney injury versus 105 of the 4140 patients (2.5%) without severe acute kidney injury (P<0.001). Severe acute kidney injury was associated with increased use of mechanical ventilation and renal-replacement therapy. A stepwise increase in 28-day mortality was associated with worsening severity of acute kidney injury (P<0.001 by log-rank test). Assessment of acute kidney injury according to the plasma creatinine level alone failed to identify acute kidney injury in 67.2% of the patients with low urine output.

Conclusions: Acute kidney injury is common and is associated with poor outcomes, including increased mortality, among critically ill children and young adults. (Funded by the Pediatric Nephrology Center of Excellence at Cincinnati Children's Hospital Medical Center and others; AWARE ClinicalTrials.gov number, NCT01987921 .).

Figure 1. Screening, Eligibility, and 28-Day Primary Outcome

The primary outcome was death by day 28 after admission to the pediatric intensive care unit (ICU). The 253 patients who did not have 28-day data were excluded from outcome analyses. The maximum stage of acute kidney injury was defined as the highest stage observed during the first 7 days after ICU admission. The stages of acute kidney injury were defined according to the Kidney Disease: Improving Global Outcomes plasma creatinine criteria (stage 1: an increase in the creatinine level to 1.5 to 1.9 times the baseline level that is known or presumed to have occurred within the past 7 days or an increase by ≥0.3 mg per deciliter [26.5 µmol per liter] within the past 48 hours; stage 2: a level 2.0 to 2.9 times the baseline level; stage 3: a level 3.0 times the baseline level, an increase to ≥4.0 mg per deciliter [354 µmol per liter], or, in patients <18 years of age, a decrease in the estimated glomerular filtration rate to <35 ml per minute per 1.73 m²) and urine-output criteria (stage 1: <0.5 ml per kilogram of body weight per hour for 6 to <12 hours; stage 2: <0.5 ml per kilogram per hour for ≥12 hours; stage 3: <0.3 ml per kilogram per hour for ≥24 hours or anuria for ≥12 hours).

Figure 2. Kaplan–Meier Survival Curves According to Maximum Stage of Acute Kidney Injury (AKI_max)

Death occurred in four patients in whom AKI_max was unknown; these patients were excluded from the analysis. The inset shows the same data on an expanded y axis.

Figure 3. Prevalence of Acute Kidney Injury, According to Stage, during the First Week of ICU Admission

For day 0, only the serum creatinine level was used to assess for acute kidney injury because data on urine output were not available. Patients with missing data to assess for acute kidney injury were excluded from analysis.