Patients undergoing for aortic valve replacement will be enrolled in the study after giving the signed informed consent and will be divided in two groups depending on the type of the surgical technique. Either full sternotomy (FS) or minimal invasive sternotomy (MIS) will be performed, both with the use of cardio-pulmonary bypass (CPB).One week before and one week after the surgery patients will undergo mini mental test and measurement of visually evoked cerebral blood flow velocity response (VEFR).Levels of S100B, interleukin (IL) 1, IL 6, IL 8, IL 10 and microparticles will be determined before induction of anesthesia,as well as 6 h, 24 h, 48 h and 7 days after CPB.Each patient will have invasive and non invasive monitoring that will include near infrared spectroscopy (NIRS), bispectral index (BIS) and TCD during surgery.MES will be detected using TCD at the following time-points: beginning of surgery, after sternotomy, during aortic cannulation, during CPB, during de-airing, opening of the clamp on the aorta and after CBP removal before chest closure.All of this data will be documented as well as the demographic characteristics of patients, their preoperative medical status, and intraoperative data (duration of surgery, duration of CPB, hemodynamic parameters, inotropic/vasoactive support,blood and blood components); duration of mechanical ventilation in intensive care unit (ICU), duration of ICU stay, 30-day mortality and morbidity, as well as postoperative complications.