Altered Mental Status During Critical Illness: Delirium and Coma

altered mental status secondary to their acute disease processes or as a consequence of the therapies used to treat disease. These mental status changes range from coma to hyperactive delirium. A comatose patient is unresponsive to physical or verbal stimuli, whereas delirium is an acute and fluctuating disorder of consciousness characterized by inattention, disorganized thinking, and perceptual disturbances (Figure 1). Alterations in mental status have traditionally been considered expected consequences of critical illness, and clinicians are increasingly aware that these mental status changes are manifestations of acute brain organ dysfunction that are associated with worse clinical outcomes. Early studies evaluating coma and delirium were hampered by the many different terms (eg, confusional state, ICU psychosis, acute brain dysfunction, and encephalopathy) used to describe altered mental status during critical illness. Additionally, the lack of validated bedside tools (besides the comprehensive Chapter 1