Background: Acute kidney injury (AKI) is a significant complication in pediatric patients undergoing cardiac surgery. Iron metabolism-related indicators such as ferritin may predict AKI after adult cardiac surgery. However, it remains unclear whether ferritin can be used as a predictor of AKI after pediatric cardiac surgery. This study aims to investigate the association between preoperative serum ferritin levels and the risk of AKI in pediatric population. Methods: A prospective observational cohort study included 6088 pediatric patients (aged <16 years) who underwent cardiac surgery between 2022 and 2023 in Fuwai hospital. Preoperative serum ferritin levels were measured. The primary outcome was the occurrence of AKI within 7 days postoperatively, diagnosed per KDIGO criteria. Secondary outcomes included severe AKI (KDIGO stages 2 and 3), postoperative dialysis, and in-hospital mortality. Results: The preoperative serum ferritin demonstrated a J-shaped association with the occurrence of AKI. Categorically, higher serum ferritin levels (>300μg/L, 150-300μg/L and 80.6-150μg/L) significantly increased the risk of AKI compared to lower level (40-80.6μg/L) (adjusted OR, 3.468; 95% CI, 1.911-6.291; adjusted OR, 3.142; 95% CI, 2.037-4.8451; and adjusted OR, 1.880; 95% CI, 1.299-2.495; respectively). The risk of stage 2 and stage 3 AKI significantly increased with higher serum ferritin categories compared to lower level (adjusted OR, 4.428; 95% CI, 1.631-12.026; adjusted OR, 3.707; 95% CI, 1.710-8.035; and adjusted OR, 2.345; 95% CI, 1.220-4.505; respectively). As a continuous variable, consistent with categorical variables, elevated serum ferritin levels (>80.6μg/L) independently predicted AKI (adjusted OR, 1.001; 95% CI, 1.000-1.002). Conclusions: This study highlights the importance of preoperative serum ferritin levels in predicting AKI risk in pediatric patients undergoing cardiac surgery. Further research is warranted to elucidate the underlying mechanisms and explore the therapeutic implications of ferritin monitoring in clinical practice. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT05489263.

The authors have declared no competing interest.

NCT05489263

This study was supported by the Chinese Academy of Medical Sciences Central Public Welfare Scientific Research Institute Basal Research Expenses-Clinical and Translational Medicine Research Fund (2021-I2M-C&T-B-036). The study sponsors and funding agencies did not participate in the study design and will not be involved in the collection, management, analysis, or interpretation of the data, or in the preparation and submission of the manuscript.

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The ethical review for our study was conducted by the Ethics Committee of Fuwai Hospital, CAMS&PUMC, affiliated with Fuwai Hospital, National Center of Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College. The committee reviewed our study and granted ethical approval. As this was an observational study, written informed consent was not obtained individually. Instead, a general consent form covering the use of de-identified patient data for research purposes is signed by all patients at the time of admission to our hospital.

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The data underlying this article and statistical analysis plan will be shared with researchers on reasonable request to the corresponding author. Participant data with identifiers are not openly available for access. Deidentified participant data supporting the findings of this study will be available at the time of publication. Please contact the Dr. Wang's email: stewenwang@sina.com for data-related queries or requests.