Mild postoperative acute kidney injury and outcomes after surgery for congenital heart disease

Objective: The effect of mild acute kidney injury (AKI) on outcomes after heart surgery in children is unclear. We sought to characterize the epidemiology of mild AKI associated with surgery for congenital heart disease (CHS-AKI) in children. Methods: We conducted a single-center, retrospective cohort study of 693 patients (aged 6 days-18 years) who underwent heart surgery in 2009. The prevalence of AKI within 72 hours of surgery was determined using the 3-stage Acute Kidney Injury Network criteria. Factors associated with both hospital length of stay and AKI were used in a proportional hazards model to test the association of stage 1 AKI with hospital length of stay. Results: The median age of the patients was 11.5 months (interquartile range, 3-54 months). Eighteen percent of the cohort had single ventricle heart disease and 54% underwent RACHS-1 category 3 or higher surgery. The prevalence of stages 1, 2, and 3 AKI in this cohort was 11% (n = 77), 3% (n = 19), and 1% (n = 8), respectively. Factors independently associated with AKI were prematurity, single ventricle physiology, peak postoperative lactic acid concentration, cardiopulmonary bypass time, and a history of heart surgery. Stage 2 or greater CHS-AKI was associated with hospital length of stay (adjusted hazard ratio [AHR], 0.53; 95% confidence interval [CI], 0.33-0.87; P = .01), but stage 1 was not (AHR, 0.85; 95% CI, 0.66-1.10; P = .22). Conclusions: AKI occurs after surgery for congenital heart disease but may be less common than previously reported. Although moderate to severe CHS-AKI is independently associated with prolonged recovery after heart surgery, mild disease does not appear to be.