Background: Delirium is a diagnosis that can be quite elusive to physicians and medical care providers; nearly 75% of cases are missed on initial conventional clinical assessment. Patients with delirium have an in-hospital mortality rate of 22 to 76%, which is on a par with rates associated with acute myocardial infarction and sepsis. Patients with delirium can be difficult to evaluate as the presentation can be confused with a psychiatric disorder. Given the high mortality rates associated with delirium and the multiple conditions that can cause delirium, providers must be careful to consider this diagnosis carefully before other less life-threatening diagnoses are entertained. The initial discussion must begin by defining what is meant by the term delirium. Defined by both the DSM-IV-TR and the ICD 10 diagnostic criteria, the basic features include impairment of consciousness, thinking, memory, psychomotor behavior, perception, and emotion. Delirium is usually caused by some systemic insult that results in an acute confusional state and is marked by a transient impairment of attention. One key point is that the disturbance of thinking develops over a short period of time and can fluctuate throughout the day, distinguishing the disease from dementia. However, it has been noted that up to two thirds of cases of delirium occur in patients with dementia, making the distinction between the two somewhat challenging. Delirium reflects a state in which there is impaired cognitive functioning generally as a result of an acute or subacute pathological process that needs to be addressed. In all cases, delirium has an organic etiology, and can never be explained by a psychiatric condition itself.
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