<P> Delirium represents an organically caused decline from a previously attained level of cognitive functioning . It is a corollary of these differential criteria that a diagnosis of delirium cannot be made without a previous assessment, or knowledge, of the affected person's baseline level of cognitive function . In other words, a mentally disabled or demented person who is operating at their own baseline level of mental ability might appear to be delirious without a baseline functional status against which to compare . </P> <P> Some mental illnesses, such as a manic episode of bipolar disorder, depersonalization disorder, or some types of acute psychosis may cause a rapidly fluctuating impairment of cognitive function and ability to focus . Outwardly this appears similar to a confused state caused by inadequate brain metabolism but it actually comes from problems in functioning . However, they are not technically causes of delirium, since any fluctuating cognitive symptoms that occur as a result of these mental disorders are considered by definition to be due to the mental disorder itself, and to be a part of it . Thus, physical disorders can be said to produce delirium as a mental side - effect or symptom, although primary mental disorders which produce the symptom cannot be put into this category once identified . However, such symptoms may be impossible to distinguish clinically from delirium resulting from physical disorders, if a diagnosis of an underlying mental disorder is yet to be made . </P> <P> Multiple guidelines recommend that delirium should be diagnosed when it presents to healthcare services . Much evidence suggest, however, that delirium is greatly underdiagnosed . Higher rates of detection of delirium in general settings (for the ICU see below) can be assisted by the use of validated delirium screening tools . Many such tools have been published . They differ in duration, complexity, need for training, and so on . Examples of tools in use in clinical practice are: Delirium Observation Screening Scale, the Nursing Delirium Screening Scale (Nu - DESC), the Confusion Assessment Method, the Recognizing Acute Delirium As part of your Routine (RADAR) tool and the 4 "A" s Test or 4AT . </P> <P> In the ICU, international guidelines recommend that every patient gets checked for delirium every day (usually twice or more a day) using a validated clinical tool . The two most widely used are the Confusion Assessment Method for the ICU (CAM - ICU) and the Intensive Care Delirium Screening Checklist (ICDSC). There are translations of these tools in over 20 languages and they are used globally in many thousands of ICUs, and instructional videos and myriad implementation tips are available . It is not as important which tool is used as that the patient gets monitored . Without using one of these tools, 75% of ICU delirium is missed by the practicing team, which leaves the patient without any likely active interventions to help reduce the duration of his / her delirium . </P>

Delirium is an often reversible condition involving a disturbance of consciousness