Delirium in the intensive care unit

Recent advances in critical care medicine have improved survival in patients cared for in intensive care units (ICUs) worldwide, and in doing so they have revealed a major public health concern that previously had been under-appreciated. Critical care clinicians have historically been attuned to pulmonary, cardiac, and renal dysfunction as a source of morbidity and mortality in ICU patients but have underestimated the impact of brain dysfunction [1]. Delirium, a common manifestation of acute brain dysfunction in critically ill patients, is associated with poor short-term outcomes and may result in adverse sequelae years after ICU discharge [2-4], and an executive summary on preventable medical injuries commissioned by the American Association of Retired Persons identified delirium as one of six leading causes of injuries associated with hospitalization in patients over 65 years of age [5]. In this article we provide a general overview of the research to date regarding the epidemiology, diagnosis, and pathophysiology of ICU delirium, its association with health outcomes, and possible options for prevention and treatment.Delirium is defined in the American Psychiatric Association's (APA) Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV [6] as a disturbance of consciousness and cognition that develops over a short period of time (hours to days) and fluctuates over time. Many different terms have been used to describe this syndrome of cognitive impairment in critically ill patients, including ICU psychosis, ICU syndrome, acute confusional state, encephalopathy, and acute brain failure [1,7]. However, the critical care literature has recently conformed to the recommendations of the APA and other experts that the term 'delirium' be used uniformly to describe this syndrome of brain dysfunction.The prevalence of delirium reported in medical and surgical ICU cohort studies has varied from 20% to 80%, depending upon severity of illness observed and diagnostic me