Modifiable risk factors in type 1 cardiorenal syndrome in children with congenital heart disease: a retrospective cohort study

Acute kidney injury (AKI) is a frequent complication in neonates undergoing surgical correction of congenital heart defects (CHD), associated with increased morbidity and mortality. However, evidence from Central Asian pediatric populations remains scarce, particularly regarding timing, severity, and perioperative risk factors. A retrospective cohort study was conducted at the Pediatric Cardiac Intensive Care Unit of UMC “Heart Center,” Astana, Kazakhstan (January 2023–July 2024). Postoperative AKI was defined and staged according to Kidney Disease: Improving Global Outcomes (KDIGO) neonatal criteria, using both serum creatinine and hourly urine output within the first 7 postoperative days and throughout the ICU stay. Clinical, laboratory, and perioperative factors, including gestational age, birth weight, intraoperative bleeding, blood pressure, and cardiopulmonary bypass (CPB) duration, were analyzed. Renal replacement therapy (peritoneal dialysis or continuous renal replacement therapy) was initiated based on oliguria, rising creatinine, or electrolyte imbalance. Among 124 neonates, 74 (59.7%) developed AKI, most within the first postoperative week. The maximum AKI stages were: stage 1–30/74 (40.5%), stage 2–24/74 (32.4%), and stage 3–20/74 (27.0%). Renal replacement therapy was required in 22/124 (17.7%) patients (peritoneal dialysis in 18, CRRT in 4). AKI was associated with lower gestational age, lower birth weight, prolonged CPB, and intraoperative hypotension. In multivariable analysis, sepsis (HR 3.5, p = 0.01), male sex (HR 1.8, p = 0.04), and hyponatremia (< 130 mmol/L; OR 4.1, p < 0.001) independently predicted AKI. The “age” variable reflected minor postnatal age differences within the neonatal period. AKI was associated with longer ICU stay and higher mortality (33.3% vs. 0%, p < 0.001). Postoperative AKI is common in neonates undergoing corrective CHD surgery and is strongly associated with perioperative instability and sepsis. Early recognition and timely renal support, including peritoneal dialysis as a supportive measure, may improve short-term management. These findings provide region-specific data from a Central Asian tertiary center and underscore the importance of systematic renal monitoring in resource-limited pediatric settings.