Delirium is an acute state of confusion marked by sudden onset, fluctuating course, inattention, and at times an abnormal level of consciousness (1). Delirium is extremely common but can be challenging to diagnose. Its manifestations range from acute agitation, which accounts for less than 25% of all cases (1), to the much more common but less frequently recognized hypoactive, or quiet, variant. Delirium, which is an acute change in mental status, must be differentiated from dementia, which is usually characterized by a slower progression. However, delirium and dementia frequently coexist. Approximately one third of patients aged 70 years or older admitted to the general medical service of an acute care hospital experience delirium: One half of these are delirious on admission to the hospital; the other half develops delirium in the hospital (1). Postoperative delirium rates among seniors range from 15% to 25% after elective surgery (2), such as total joint replacement, to over 50% after high-risk procedures, such as hip fracture repair and cardiac surgery (3, 4). Among patients of any age admitted to intensive care units (ICUs), the prevalence of delirium may exceed 75% (5), and the cumulative incidence of delirium at the end of life is reported to be as high as 85% (6).