Navigating Hemolysis and the Renal Implications of Hemoglobin Toxicity in Cardiac Surgery

Cardiac surgery with cardiopulmonary bypass (CPB) is associated with acute kidney injury (AKI), which presents a substantial clinical challenge.^1,2  AKI occurs in 20 to 30% of patients without known kidney disease.³  However, the prevalence can be as high as 50% in high-risk populations and those undergoing complex procedures such as multiple valve replacements or combined valvular and coronary artery procedures, which require long-duration CPB time (more than 4 h). Postoperative AKI necessitates additional patient monitoring, extended hospitalization times, increased healthcare costs, and increased morbidity and mortality.^4–7  Patients who experience AKI after cardiac surgery—even if transient—have an increased risk of chronic and end-stage renal disease in the long term, underscoring the condition’s far-reaching impact on public health.^8,9 

This review systematically examines CPB-induced hemolysis and the contribution of cell-free hemoglobin (CFHb) toxicity to AKI. First, we describe the molecular mechanisms of CFHb toxicity and...