This study investigates the relationship between cerebral overperfusion and postoperative delirium (POD) in cardiac surgery patients. Despite reduced cortical metabolism, patients with POD exhibited increased cerebral blood flow, measured via transcranial Doppler. Low bispectral index (BIS) values indicated reduced metabolism, but no differences in autoregulation impairments were noted. The findings suggest a mismatch between cerebral blood flow and metabolism contributes to POD, independent of cerebral autoregulation.