Association Between Progression and Improvement of Acute Kidney Injury and Mortality in Critically Ill Children*

OBJECTIVE: To determine whether the progression and/or improvement of acute kidney injury in critically ill children is associated with mortality. DESIGN: Retrospective. SETTING: Multidisciplinary, tertiary care, 24-bed PICU. PATIENTS: A TOTAL OF: 8,260 patients who were 1 month to 21 years old with no chronic kidney disease admitted between May 2003 and March 2012. INTERVENTIONS: We analyzed patients based on their acute kidney injury stage as per the Kidney Disease Improving Global Outcomes acute kidney injury serum creatinine staging criteria on ICU admission, peak (highest acute kidney injury stage reached), and trough (lowest acute kidney injury stage after the peak) during their ICU stay. Nonrenal organ dysfunction was measured with a modified Pediatric Logistic Organ Dysfunction score. The primary outcome was 28-day mortality. p values were based on Yates-corrected chi-square test and logistic regression. MEASUREMENTS AND MAIN RESULTS: Of the 8,260 patients, 529 (6.4%) had acute kidney injury on ICU admission and 974 (11.8%) had acute kidney injury during their ICU course. The 28-day mortality was 2.7% for patients with no acute kidney injury and 25.3% for patients with acute kidney injury. Patients in whom acute kidney injury developed or had worsening acute kidney injury from admission to peak and reached acute kidney injury stage 2 or 3 had higher mortality than those who remained at an acute kidney injury stage 1 (17.3-17.8% vs 32.2-37.9%; p ≤ 0.003). Patients whose acute kidney injury resolved after the peak had lower mortality than those who retained the same degree of acute kidney injury (9-13.5% vs 37.3-44%; p ≤ 0.04). Patients with acute kidney injury that resolved still had higher mortality than those who never developed acute kidney injury (11.2% vs 2.7%; p < 0.001). Multivariate regression demonstrated that the association between mortality and acute kidney injury progression was independent of severity of illness at admission and the severity of nonrenal organ dysfunction during the first week of ICU stay (p ≤ 0.01). CONCLUSION: Progression of acute kidney injury per the Kidney Disease Improving Global Outcomes staging criteria is independently associated with increased mortality in the PICU while its improvement is associated with a stepwise decrease in mortality.