Biomarkers of Postoperative Complications After Cardiac Surgery

Postoperative delirium and other complications are important adverse outcomes following cardiac surgery. This study will integrate perioperative clinical information with molecular measurements to investigate factors associated with these outcomes and improve early risk assessment.

Eligible patients undergoing elective coronary artery bypass grafting, cardiac valve surgery, or combined procedures will be prospectively enrolled. Data collection will include demographic characteristics, medical history, preoperative medications, laboratory findings, surgical and anesthetic characteristics, and postoperative clinical outcomes.

Blood samples will be collected before surgery and approximately 24 hours after surgery, processed according to standardized procedures, and stored for subsequent analyses. Molecular investigations will include proteomic and metabolomic profiling and targeted measurement of selected biomarkers.

POD will be assessed twice daily by trained research personnel during the first 7 postoperative days or until hospital discharge, whichever occurs first. Standardized, validated delirium assessment instruments will be used in the ICU and after transfer to the ward. Other postoperative complications and recovery outcomes will be recorded prospectively.

Analyses will examine associations between clinical characteristics, molecular profiles, and postoperative outcomes. Causal inference methods will be used, where appropriate, to explore the potential causal relevance of candidate biomarkers under explicitly stated assumptions. Interpretable prediction models will be developed using clinical variables, molecular features, or their combination. Model performance will be assessed in terms of discrimination, calibration, and potential clinical utility. Internal validation will be performed, and temporal or external validation will be undertaken where suitable independent data are available.