Postoperative Cognitive Disorders (POCD) are common in hospitalized people > 60 year old, especially in orthopedic patients. Etiology of POCD is complex, and in some aspects still remains unclear. The role of thromboembolic events in etiology of POCD was discussed. The incidence of such events in patients who underwent big joints arthroplasty can be as high as 40 to 60%, although some cases are subclinical. Thromboembolic material can block a blood flow through a vessels in the brain. As a consequence cerebral neurons can be damaged or destroyed. After neuronal damage specific substances, such as S100B protein, glial fibrillary acidic protein (GFAP) and neuron-specific enolase (NSE) are released to the blood. The serum concentrations of these biomarkers can be measured. Moreover, the block of blood flow will decrease regional cerebral saturation in affected parts of the brain.