Objective. To evaluate the prognostic significance of oxygen supply to the brain in the risk of neurological complications in the early post operative period of surgical treatment of the ascending aorta and aortic arch. Material and methods. The level of oxygenation (rSO2) in the right and left hemispheres was measured in 68 patients with ascending aorta and aortic arch chronic dissection. Before and in the nearest period after surgery, the patients underwent a clinical/instrumental neurological study. Results. The incidence of ischemic stroke in the early post operative period was 5.9%, cognitive impairment was recorded in 22% of patients. Among the parameters of oxygen supply to the brain, the dynamics of rSO2 during circulatory arrest had a significant impact on the post operative neurological status. The risk of cognitive impairment, besides the association with the oxygen status of the brain, increased with the age of patients and comorbid pathology. Conclusion. The decrease in rSO2 by ≥30% during surgical treatment of ascending aorta and aortic arch dissection increases the risk of ischemic stroke and cognitive impairment in the early post operative period.