Up to 50% of patients over 60 years old develop postoperative delirium following cardiac surgery. Delirium increases morbidity and mortality, and may lead to long-term cognitive impairment similar to patients with a diagnosis of Alzheimer's disease. The underlying mechanisms behind delirium are not understood, and therefore the current prevention and treatment strategies are inadequate. Several hypotheses exist for the pathophysiology of delirium, one of which is the role of neuroinflammation. The stress associated with high-risk procedures such as cardiac surgery may lead to systemic inflammation causing endothelial dysfunction and disruption of the blood brain barrier (BBB). When this occurs, the brain is susceptible to neuronal injury via neuroinflammation after which a state of delirium may ensue. To characterize the mechanisms of neuroinflammation in delirium, the investigators will explore the biomarkers most closely linked to each step of the proposed pathway.