Heart surgery is frequently followed by confusion (delirium) in the days immediately after surgery, but also long-term cognitive decline in the following months/years. Presently, there is no effective therapy for preventing these conditions. Administering high dose insulin during surgery was previously shown to improve short and long-term memory function; however this type of treatment is hard to administer and perhaps risky. Previous findings in animals and patients suggest that administering insulin through the nose (intranasal insulin) may be effective in reducing delirium and cognitive decline after heart surgery. Collaborators at McGill University will conduct a study in 500 patients undergoing heart surgery comparing intranasal insulin daily for 7 days around surgery and placebo. Investigators at the National Institute on Aging will process blood samples of these patients to extract small particles that come from brain cells called  Extracellular Vesicles or exosomes. They will measure various chemicals (biomarkers) to investigate if insulin treatment changes these markers in a positive way reflecting changes in the  brain cells from where these exosomes originated.