The development of complications after coronary artery bypass grafting (CABG) is caused by reperfusion syndrome due to the restoration of blood flow in the ischemic zone, the main pathogenetic mechanism of which is oxidative stress. The study of changes in iron levels was carried out based on the determination of serum iron (Fe), transferrin (Tr), total serum iron binding capacity (OGCC), latent blood iron binding capacity, LVCC, ferritin (F) in blood plasma. There were no restrictions on the total concentration of nitrites and nitrates – NOx in the blood. According to the degree of intraoperative hemolysis (IOH), determined by the level of free hemoglobin, Hbsp., patients with coronary artery bypass surgery (CABG) were divided into 3 groups: group 1 – without IOH (Hbsp <0.1 g/l), h =43, group 2 – with low IOH (nIOH) with Hbs. >0.1 g/l and <0.5 g/l, n=42, group 3 with high IOG (vIOG) – Hbs.≥0.5 g/l, N=38. In patients with a high risk of changes in bi-lo indicators, the maximum was an increase of 91.9%, p <0.001, [F] – by 165.9% (p<0.001), a decrease of 22.0%, p <0.001, and LVH – by 45.0%, p <0.001. In the group without IOG change. The studied indicators of the iron pool were not revealed. At the end of CABG, compared with the baseline value, there was a decrease in [Nox] in blood plasma and its increase within 5-7 days after surgery, to the greatest extent in the group with vIOG. The revealed changes in the iron pool in patients with coronary bypass surgery indicate the influence of iron on the activity of oxidative processes, predisposing to the development of complications. This is confirmed by the nature of changes in the concentration of nitrites and nitrates, which depended on the severity of intraoperative hemolysis, indicating the effect of hemolysis products, including iron, on the formation and utilization of nitric oxide.