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Table 47-3 lists instruments for identification of delirium. Of these, the most widely used is the CAM, of which the four-item short form has been applied in over 4000 studies to date and translated into over 14 languages. The CAM has also been adapted for use in other settings, including the intensive care unit (CAM-ICU), nursing home (NH-CAM), and emergency department (CAM-ED and B-CAM). A new adaptation, called the 3D-CAM, provides a brief cognitive assessment that takes fewer than 3 minutes to complete, and identifies delirium with high sensitivity and specificity. The CAM-S derived from the CAM can be used to rate delirium severity, and has demonstrated predictive validity for relevant clinical outcomes. Other delirium severity instruments include the Delirium Rating Scale (DRS-98), the Memorial Delirium Assessment Scale (MDAS), and the Delirium Index (DI). Each instrument has strengths and limitations, and the choice among them depends on the goals for use.
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The acute evaluation of suspected or confirmed delirium centers on three main tasks that occur simultaneously: (1) establishing the diagnosis of delirium; (2) determining the potential cause(s) and ruling out life-threatening contributors; and (3) managing the symptoms while assuring patient safety. Delirium is a clinical diagnosis, relying on astute observation at the bedside, careful cognitive assessment, and history-taking from a knowledgeable informant to establish a change from the patient’s baseline functioning. Identifying the potentially multifactorial contributors to the delirium is of paramount importance, because many of these factors are treatable, and if left untreated, may result in substantial morbidity and mortality. Because the potential contributors are myriad, the search requires a thorough medical evaluation guided by clinical judgment. The challenge is enhanced by the frequently nonspecific or atypical presentation of the underlying illness in older persons. In fact, delirium is often the only sign of life-threatening illness, such as sepsis, pneumonia, or myocardial infarction in older persons. The NICE guidelines on delirium provide a recent systematic review and evidence-based approach to delirium (http://www.nice.org.uk/guidance/CG103). These guidelines highlight both the importance of delirium in older persons, and the need for better recognition and prevention of delirium.
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History and Physical Examination
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A thorough history and physical examination constitute the foundation of the medical evaluation of suspected delirium. The first step in evaluation should be to establish the diagnosis of delirium through careful cognitive assessment and to determine the acuity of change from the patient’s baseline cognitive state. Because cognitive impairment may easily be missed during routine conversation, brief cognitive screening tests, such as the Short Portable Mental Status Questionnaire, Mini-Cog test, or 3D-CAM assessment, should be used to rate the CAM. The degree of attention should be further assessed with simple tests such as a forward digit span (inattention indicated by an inability to repeat five digits forward or three digits backwards) or recitation of the months of the year backward. A targeted history, focusing on baseline cognitive status and chronology of recent mental status changes, should be elicited from a reliable informant (eg, family member or health professional). In addition, such historical data as intercurrent illnesses, recent adjustments in medications, the possibility of alcohol withdrawal, and pertinent environmental changes may point to potential precipitating factors of delirium.
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The physical examination should include a detailed review that focuses on potential etiologic clues to an underlying or inciting disease process. Vital sign assessment is important to identify fever, tachycardia, or decreased oxygen saturation, each of which may point to specific disease processes. Ausculatory examination may suggest pneumonia or pulmonary effusion. A new cardiac murmur or dysrhythmia may suggest ischemia or congestive heart failure. Gastrointestinal examination should focus on evidence of an acute abdominal process, such as occult bleeding, perforated viscus, or infection. Patients with delirium may also demonstrate nonspecific focal findings on neurologic examination, such as asterixis or tremor, although the presence of any new neurologic deficit should raise suspicion of an acute cerebrovascular event or subdural hematoma. It is worthy of emphasis that in many older patients and in those with cognitive impairment, delirium may be the initial manifestation of a serious new disease process. Therefore, attention to early localizing signs on serial physical examinations is important.
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A complete medication review, including over-the-counter medications, is critical, and any medications with known psychoactive effects should be discontinued or minimized whenever possible. Because of pharmacodynamic and pharmacokinetic changes in aging adults, these medications may cause deleterious psychoactive effects even when prescribed at customary doses and with serum drug levels that are within the “therapeutic range.”
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Laboratory Tests and Imaging
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Despite the growing recognition of geriatric syndromes such as delirium, there is little evidence-based research that assesses the predictive value of laboratory and other diagnostic testing in the evaluation of delirium. Consequently, laboratory evaluation should be guided by clinical judgment and take into account specific patient characteristics and historical data. An astute history and physical examination, medication review, focused laboratory testing (eg, complete blood count, chemistries, glucose, renal and liver function tests, urinalysis, oxygen saturation), and search for occult infection should help to identify the majority of potential contributors to the delirium. Obtaining additional laboratory testing such as thyroid function tests, B12 level, cortisol level, drug levels or toxicology screen, syphilis serologies, and ammonia level should be based on a patient’s distinct clinical presentation. Further diagnostic work-up with an electrocardiogram, chest radiograph, and/or arterial blood gas determination may be appropriate for patients with pulmonary or cardiac conditions. The indications for cerebrospinal fluid examination, brain imaging, or EEG remain controversial. Their overall diagnostic yield is low, and these procedures are probably indicated in fewer than 5% to 10% of delirium cases. Lumbar puncture with cerebrospinal fluid examination is indicated for the febrile delirious patient when meningitis or encephalitis is suspected. Brain imaging (such as CT or MRI) should be reserved for cases with new focal neurologic signs, with history or signs of head trauma, or without another identifiable cause of the delirium. Of note, some neurologic symptoms are associated with delirium, including tremor and asterixis. EEG, which has a false-negative rate of 17% and a false-positive rate of 22% for distinguishing between delirious and nondelirious patients, plays a limited role and is most commonly employed to detect subclinical seizure disorders and to differentiate delirium from nonorganic psychiatric conditions.
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Differential Diagnosis
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Distinguishing a long-standing confusional state (dementia) from delirium alone, or from delirium superimposed on dementia, is an important, but often difficult, diagnostic step. These two conditions can be differentiated by the acute onset of symptoms in delirium, with dementia presenting much more insidiously and by the impaired attention and altered level of consciousness associated with delirium.
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The differential diagnosis of delirium can be extensive and includes other psychiatric conditions such as depression and nonorganic psychotic disorders (Table 47-4). Although perceptual disturbances, such as illusions and hallucinations, can occur with delirium in about 15% of cases, recognition of the key features of acute onset, inattention, altered level of consciousness, and global cognitive impairment will enhance the identification of delirium. Differentiating among diagnoses is critical because delirium carries a more serious prognosis without proper evaluation and management, and treatment for certain conditions such as depression or affective disorders may involve use of drugs with anticholinergic activity, for example, which could exacerbate an unrecognized case of delirium. At times, working through the differential diagnosis can be quite challenging, particularly with an uncooperative patient or when an accurate history is unavailable, and the diagnosis of delirium may remain uncertain. Because of the potentially life-threatening nature of delirium, however, it is prudent to manage the patient as having delirium and search for underlying precipitants (eg, intercurrent illness, metabolic abnormalities, adverse medication effects) until further information can be obtained.
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Algorithm for the Evaluation of Altered Mental Status
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Figure 47-2 presents an algorithm for the evaluation of altered mental status in the older patient. The initial steps center on establishing the patient’s baseline cognitive functioning and the onset and timing of any cognitive changes. Chronic impairments, representing changes that occur over months to years, are most likely attributable to a dementia, which should be evaluated accordingly (see Chapter 66). Acute alterations, representing abrupt deteriorations in mental status, occur over hours to weeks, although they may be superimposed on an underlying dementia. They should be further evaluated with cognitive testing to establish the presence of delirium. In the absence of notable delirium features (see “Presentation” earlier in this chapter), subsequent evaluation should focus on the possibility of major depression, acute psychotic disorder, or other psychiatric disorders (see Chapters 71,72,73).
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