Minimizing ICU Neurological Dysfunction With Dexmedetomidine-induced Sleep (MINDDS II)

Inclusion Criteria: * Aged 60 years or older * Scheduled to undergo a cardiac surgical procedure with cardiopulmonary bypass * Planned postoperative admission to the intensive care unit (ICU) Exclusion Criteria: * Allergy or hypersensitivity to dexmedetomidine or the placebo study medication * Preexisting diagnosis of Alzheimer's Disease or Related Dementia, severe cognitive impairment or delirium at baseline * Severe liver failure (Child-Pugh score \> 5) * Severe deficit(s) due to structural or anoxic brain damage * Undergoing a surgical procedure requiring total circulatory arrest * SARS-CoV-2 positive or symptomatic (e.g., fever, cough, loss of taste/smell) * Blind, deaf, or unable to communicate in English * Patients experiencing circumstances for which long-term follow-up might be difficult (e.g., homelessness, active psychotic disorder, or substance abuse) * Co-enrollment in other interventional studies that, in the opinion of the site investigator and/or PI, might interfere with study participation, collection, or interpretation of the study data