Cognitive dysfunction (CD) is quite common in critically ill patients, not only during the acute illness but also long after the acute illness resolves [5] . Delirium, a form of acute CD that manifests as a fluctuating change in mental status, with inattention and altered level of consciousness, occurs in as many as 80% of mechanically ventilated intensive care unit (ICU) patients [6] . Most clinicians consider ICU delirium to be expected, iatrogenic, and without consequence. However, recent data associate delirium with increased duration of mechanical ventilation and ICU stay [7] , worse 6-month mortality [8] , and higher costs [9] . Chronically, critical illnessassociated CD manifests as difficulties with memory, attention, executive function, mental processing speed, spatial abilities, and general intelligence. Interestingly, patients who develop acute CD often go on to develop chronic CD after hospital discharge [10] [11] [12] [13] , suggesting that the two entities may share a common etiology.