Postoperative cognitive dysfunction (POCD) describes a decline in cognitive function as measured by pre- and postoperative neuropsychological testing. It is common after cardiac surgery, affecting 25% to 70% of patients, and is usually associated with pathophysiological mechanisms such as cerebral hypoperfusion, cerebral microemboli, glycaemic control and neurotoxic effects of anaesthetic agents. There are similar mechanisms between POCD and postoperative delirium (POD), both of which promote neuroinflammation through systemic inflammation and blood-brain barrier dysfunction. It has also been associated with concentrations of peripheral inflammatory markers (such as CRP, IL-6). The aim of this study was to examine the pathophysiological processes leading to cognitive dysfunction after cardiac surgery and to evaluate the role of targeted fluid therapy in these conditions. Targeted fluid therapy aims to optimise fluid, inotrope and vasopressor therapy by monitoring haemodynamic parameters (stroke volume, cardiac output, systemic vascular resistance, etc.). This treatment may improve tissue perfusion, reduce the inflammatory response and reduce mortality. In this study, the optimisation of fluid therapy during cardiac surgery was achieved by using monitors based on oesophageal doppler and pulse contour analysis. The effectiveness of these methods in reducing major complications and improving clinical outcomes will be evaluated.