Serum lactate and capillary refill time as predictors of acute kidney injury after pediatric cardiovascular surgery: a prospective cohort study

BACKGROUND: Acute kidney injury (AKI) is a frequent complication after pediatric cardiovascular surgery (CS) and is associated with higher morbidity and mortality. Early, modifiable predictors are needed to improve outcomes. METHODS: We conducted a prospective cohort study at a high-complexity center in Cali, Colombia (November 2020-July 2022). Children aged 0-60 months undergoing CS and admitted to the pediatric cardiovascular ICU were included. AKI was defined and staged according to KDIGO criteria. Serum lactate and capillary refill time (CRT) were measured preoperatively, at ICU admission, and at 6, 12, and 24 h postoperatively. Univariate and multivariate Cox proportional hazards models were used to assess associations with AKI. RESULTS: Of 127 patients, 14.17% developed AKI, 66.7% of which were severe. The 28-day mortality was 11.8% overall and 44.4% among patients with AKI. In the multivariate analysis, elevated serum lactate was associated with higher risk of AKI at 24 h postoperatively (HR 1.61; 95%CI 1.24-2.08). Prolonged CRT at ICU admission was also a significant predictor (HR 1.80; 95%CI 1.03-3.15). Higher surgical complexity (RACHS-1), vasopressor use, and low systolic blood pressure were also associated with AKI. CONCLUSIONS: In this cohort, postoperative tissue perfusion markers-elevated serum lactate and prolonged CRT-were associated with AKI following pediatric CS. These accessible bedside measures may support early risk stratification and targeted kidney protective strategies.