To study the features of enzymatic and metabolic support of oxidative homeostasis in patients with hypoxic-ischemic brain lesions before and after cardiac surgery using artificial circulation we examined 38 patients, in particular: ischemic stroke — 14 people, encephalopathy — 15 people, severe cognitive dysfunction — 9 people ; diagnosis of neurological status was performed according to clinical protocols. Clinical and biochemical study was performed at the preoperative (3—5 days) and postoperative (5—7 days) stages: determined the content of superoxide dismutase, glutathione peroxidase, catalase in erythrocytes and α-tocopherol acetate in the serum of the blood, as well as the product cells: diene conjugates, metabolites of nitritanion in plasma. Variation statistics, probabilistic distribution of data with the subsequent estimation of reliability of results are applied; relative biochemical parameters were used: metabolic index, metabolic coefficient and metabolic effect for each. Standard methods using the program adapted to the “Excel” environment were used for calculations. The obtained data support the formation of patients with specific postoperative enzymatic-metabolic support of oxidative homeostasis, which should be considered as one of the triggers of hypoxicischemic brain lesions. In particular, at the level of the enzymatic chain of pro-, antioxidant protection and at the level of metabolic processes associated with peroxidation of phospholipids of cell membranes, a number of significant metabolic effects were revealed, which are generalized due to secondary oxidation products and NO-dependent metabolites.