During their routine preoperative blood draw the phlebotomist will be provided with three heparinized blood tube labeled with only the patient's study ID number that will be returned to the investigative team and processed within 30 minutes of the blood draw. Briefly, half of the sample would be spun down and plasma harvested and stored at -80 degrees C and when an adequate sample size obtained used to measure inflammatory cytokines by ELISA. The remainder of the sample will be divided into 1-ml aliquots and incubated at 37°C for 15 min with phosphate-buffered saline (PBS) (control), 100 ng/ml interleukin (IL)-6, 100 ng/ml IL-10, or a combination of 100 ng/mlIL-2 and 2 ng/ml granulocyte macrophage colony-stimulating factor, or 1g/ml lipopolysaccharide. Blood samples will be resuspended in 1.4 ml stabilizing buffer and incubated for 10 min at room temperature for fixation in PFA, cooled to 4C, and stored at 80C until further processing for flow cytometry to determine the immune response of the white blood cells to a ex-vivo immune challenge and whether these correlate with Mini-Cog score or the development of delirium.