Trajectory of AKI in hospitalized pediatric patients-impact of duration and repeat events.

Background: Peak severity of acute kidney injury (AKI) is associated with mortality in hospitalized pediatric patients. Other factors associated with AKI, such as number of AKI events, severity of AKI events and time spent in AKI, may also have associations with mortality. Characterization of these events could help to evaluate patient outcomes.

Methods: Pediatric inpatients (<19 years of age) from 2011 to 2019 who were not on maintenance renal replacement therapy and had least one serum creatinine (SCr) obtained during hospital admission were included. Percent change in SCr from the minimum value in the prior 7 days was used for AKI staging according to Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Maximum value for age appropriate normal was used for patients with only one SCr. Repeat AKI events were classified in patients if KDIGO criteria were met more than once with at least one SCr value between episodes that did not meet KDIGO criteria. Patient demographics were summarized and incidence of AKI was determined along with associations with mortality. AKI characterizations for the admission were developed including: AKI, repeat (more than one) AKI, AKI severity (maximum KDIGO stage) and total number of AKI events. AKI duration as percent admission days in a KDIGO stage and AKI percent velocity were determined. Kaplan-Meier analysis was performed for time to 30-day survival by AKI characterization. A mixed-effects logistic regression model with mortality as the dependent variable nested in patients was developed incorporating patient variables and AKI characterizations.

Results: A total of 184 297 inpatient encounters met study criteria [male 51.7%, age 7.8 years (interquartile range 2.5-13.8) and mortality 0.56%]. Hospital length of stay was 1.9 days (IQR 0.37, 4.8 days), 15.4% had an intensive care unit admission and 12.2% underwent mechanical ventilation. AKI occurred in 5.6% (n = 10 246) of admissions [Stage 1, 4.5% (n = 8310); Stage 2, 1.3% (n = 2363); Stage 3, 0.77% (n = 1423)] and repeat AKI events occurred in 1.92% (n = 3558). AKI was associated with mortality (odds ratio 6.0, 95% confidence interval 4.8-7.6; P < 0.001) and increasing severity (KDIGO maximum stage) was associated with increased mortality. Multiple AKI events were also associated with mortality (P < 0.001). Duration of AKI was associated with mortality (P < 0.001) but AKI velocity was not (P > 0.05).

Conclusions: AKI occurs in 5.6% of the pediatric inpatient population and multiple AKI events occur in ∼30% of these patients. Maximum KDIGO stage is most strongly associated with mortality. Multiple AKI events and AKI duration should also be considered when evaluating patient outcomes.