Acute renal failure after cardiopulmonary bypass is related to decreased serum ferritin levels

Acute renal failure (ARF) requiring dialysis occurs in up to 4% of patients after cardiopulmonary bypass (CPB). CPB leads to the generation of intrava scular free hemoglobin, resulting in increased endothelial and renal tubula r cell free Iron, which is associated with renal injury. Conversely, renogr otec tion is conferred by processes that upregulate heme and iron sequestra tion pathways, such as ferritin. This study evaluates the influence of free hemoglobin generation during CPB and the capacity to sequester free iron o n the occurrence of post-CPB renal insufficiency. Thirty consecutive patien ts undergoing CPB were enrolled in the study. Serum creatinine, free hemogl obin, and ferritin were measured preoperatively, at the end of bypass, and 24 and 48 h after surgery. Renal injury, as determined by an increase in th e serum creatinine greater than or equal to 25% (ARF) by 48 h after surgery , occurred in 40% (12 of 30) of patients, and dialysis was necessary in 6.6 % (2 of 30). Free hemoglobin levels increased in all patients but did nor c orrelate with postoperative ARF. However, patients with preoperative serum ferritin levels less than or equal to 130 mu g/L, the median value for the group, had a six fold greater likelihood of developing ARF compared to pati ents with levels above this value (P = 0.03). Lower serum ferritin levels a ppear to be associated with the development of ARF. Serum ferritin levels m ay signify intravascular: as well as endothelial and renal epithelial cell ability to bind free iron generated during CPB-induced hemolysis, and thus may help provide information regarding the risk for ARF.