If critical illness-associated CD were solely due to acute medication effects, it would probably resolve after the exposure has ended. However, a significant percentage of individuals developing delirium in the hospital continue to demonstrate symptoms of CD after discharge [10] [11] [12] [13] . These patients manifest decreased cerebral activity and increased cognitive deterioration, and are more likely to develop dementia than patients without delirium. Also, patients who develop delirium have a greater rate of decline on cognitive tests than do nondelirious patients [10] [11] [12] [13] . Taken together, these observations raise the possibility that some degree of occult diffuse brain injury, as a consequence of the local hypoxia, hypoperfusion, cytokine-mediated inflammation and microvascular thrombosis that characterize the multisystem organ dysfunction of critical illness, might have occurred in these patients [42] . Given that every other organ system can be damaged by these forces, it seems implausible that the brain would be uniquely spared.