Advances in cardiac medicine and anesthesia have made it possible to expand the indications for open heart surgery to increasingly older and more complex patients. This development is taking place in a demographic context where the aging of the world population has become a structural reality. However, postoperative neurocognitive complications, and in particular postoperative cognitive disorders (POCD), are not limited to the elderly. They can affect all adults, including younger adults, particularly in the presence of risk factors such as prolonged cardiopulmonary bypass, deep anesthesia, or episodes of intraoperative cerebral desaturation. The PSi-NIRS study was designed with this broad perspective in mind. It will include all adult patients (≥18 years) eligible for cardiac surgery under extracorporeal circulation, with a secondary analysis dedicated to patients aged 65 years and older, a group in which POCD is more frequent, more long-lasting, and often has more serious consequences. This division will allow to assess the impact of cerebral monitoring both in the general adult population and within a well-defined geriatric subgroup. The pathophysiological mechanisms involved in POCD are now better understood. On the one hand, insufficient cerebral oxygenation, even transient, can disrupt neuronal homeostasis for a prolonged period. On the other hand, excessively deep anesthesia, leading to periods of EEG suppression, is recognized as a risk marker for delirium and postoperative cognitive decline. These two dimensions - perfusion and cortical activity - constitute complementary targets for prevention. Independently of each other, two tools available today - near-infrared spectroscopy (NIRS) and processed electroencephalography (PSi via SedLine®) - have shown their value in cardiac surgery. The use of NIRS to guide intraoperative adjustments has been associated with a reduction in neurological complications. Anesthetic guidance by EEG makes it possible to limit periods of suppression, linked to an increased risk of delirium and POCD. However, to date, no randomized study has evaluated the combined and coordinated use of these two modalities, with a predefined therapeutic algorithm allowing real-time clinical intervention based on critical thresholds. The PSi-NIRS study is therefore part of a logic of scientific continuity, but takes a methodological step forward by testing for the first time an integrated and proactive approach to cerebral monitoring, applied to a surgical context with high neurological risk. It aims to verify whether this strategy can improve the postoperative cognitive trajectory of patients, in the short and medium term, by targeting the real points of intraoperative cerebral vulnerability.