Cardiovascular diseases are an urgent problem of modern medicine in Russia, as well as throughout the world. Ischemic heart disease (CHD) is the main cause of death and disability in the population. Coronary artery bypass grafting (CABG) is a surgical method for the treatment of coronary artery disease. Perioperative stroke is one of the most formidable complications, entailing permanent disability and an increase in the risk of death by 3-6 times. Objective: To identify blood gas parameters that affect the risk of stroke in the early postoperative period in elderly patients after CABG. Materials and methods: our work is based on the analysis of the examination results of 112 patients aged 60 to 75 years, the average age is 65.87 ± 3.44 years. All patients underwent elective coronary artery bypass grafting. 9 (8.04%) patients developed a complication in the form of stroke in the early postoperative period, six (5.36%) of whom died in the first 7 days after surgery. Results. In the course of the study, the average values of the parameters of the acid-base state of the blood were determined in all studied patients, as well as in patients with verified ACVA and without it. The ROC analysis revealed indicators that influenced the risk of stroke development; they were the partial pressure of carbon dioxide (PCO2) and lactate (Lac), and ROC curves were constructed. Cutoff thresholds have been determined. The analysis of relative risks was carried out, which confirmed the influence of these indicators on the risk of developing perioperative stroke. Conclusions. An increase in the level of PCO2 (p = 0.000; AUC = 0.987, RR = 30.00) in blood and hyperlactatemia (p = 0.000; AUC = 0.963, RR = 13.50) are reliable early postoperative predictors of stroke in elderly patients with CABG.