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Initial evaluation of delirium is largely based on establishing a patient’s baseline cognitive functioning and the clinical course of any cognitive change. Thus, a detailed history from a reliable informant, such as a spouse, child, or caregiver, is most important. The history should seek to clarify the acuity of any mental status changes and seek clues to the underlying cause.
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The cardinal historical features of delirium are acute onset and fluctuating course, in which symptoms tend to come and go or increase and decrease in severity over a 24-hour period. This is the major feature distinguishing delirium from dementia, which usually develops gradually and progressively over months to years.
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Usually determined through cognitive testing and, most importantly, close clinical observation of the quality of the patient’s response. For example, a person may score correctly on a particular cognitive task but during the task may demonstrate fluctuating attention, easy distractibility, rambling speech or lethargy.
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Decreased ability to focus, maintain and shift one’s attention. For example, patients will demonstrate difficulty maintaining or following a conversation, perseverate on a previous answer, require repetition of instructions or struggle to follow instructions on cognitive tasks (simple repetition, digit span, backward recitation of months/days).
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Disorganized thinking—
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Manifested as rambling and, at its extreme, incoherent speech. Problems with memory, disorientation, or language are frequent.
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Altered level of consciousness—
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Ranges from agitated, vigilant states to lethargic or stuporous states.
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Not essential for diagnosis but commonly seen are psychomotor agitation or retardation, perceptual disturbances (eg, hallucinations, illusions), paranoid delusions, emotional lability, and sleep-wake cycle disturbances.
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Laboratory Findings and Imaging
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The algorithm in Figure 21–1 provides a systematic approach to the diagnosis and evaluation of delirium in the older person. No specific laboratory tests exist that positively identify delirium. Current research has focused on specific biomarkers that have been promising, but all require further investigation: S-100 beta, insulin-like growth factor-1, neuron specific enolase and inflammatory markers including cytokines interleukin (IL)-8, tumor necrosis factor (TNF)-alpha, monocyte chemoattractant protein (MCP)-1, procalcitonin, and cortisol.
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Laboratory tests in the evaluation of delirious patients should include complete blood count, electrolytes (including calcium), kidney and liver function, glucose, and oxygen saturation. Furthermore, in searching for occult infection, blood cultures, urinalysis/urine culture, chest x-ray may be considered. Other laboratory tests may be pursued if specific contributing factors have not been identified in a particular patient. These include thyroid function tests, arterial blood gas, vitamin B12 levels, drug levels, toxicology screens, cortisol levels, and evaluation of the cerebrospinal fluid.
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Brain imaging with CT or MRI are indicated by a history or signs of recent fall or head trauma, fever of unknown origin, new focal neurologic symptoms, or no obvious cause has been identified. An electroencephalogram may be indicated to evaluate for occult seizure activity. It can also be used in differentiating delirium from nonorganic psychiatric disorders.
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American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed. Washington, DC: American Psychiatric Association; 2013. (Reference standard for definition of and diagnostic criteria for delirium.)
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Inouye
SK, van Dyck
CH, Alessi
CA, Balkin
S, Siegal
AP, Horwitz
RI. Clarifying confusion: the confusion assessment method. A new method for the detection of delirium.
Ann Intern Med. 1990;113(12):941-–948. (Validation study for the CAM instrument in hospitalized elderly and a subset of persons with dementia.)
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[PubMed: 2240918]
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Khan
BA, Zawahiri
M, Campbell
NL, Boustani
MA. Biomarkers for delirium—a review.
J Am Geriatr Soc. 2011;59 Suppl 2:S256-–S261. (Literature review of potential biomarkers for delirium shows promise with S-100 beta, insulin-like growth factor 1, and inflammatory markers.)
CrossRef
[PubMed: 22091570]
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Wei
LA, Fearing
MA, Sternberg
EJ, Inouye
SK. The Confusion Assessment Method: a systematic review of current usage.
J Am Geriatr Soc. 2008;56(5):823-–830. (CAM improves identification of delirium and is optimally used when scored based on observations made during formal cognitive testing and after training in the use of the instrument.)
CrossRef
[PubMed: 18384586]
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Wong
CL, Holroyd-Leduc
J, Simel
DL, Straus
SE. Does this patient have delirium? Value of bedside instruments.
JAMA[JAMA and JAMA Network Journals Full Text]. 2010;304(7):779-–786. (Eleven instruments for diagnosis of delirium were evaluated and best evidence supports use of the CAM which takes approximately 5 minutes to administer.)
CrossRef
[PubMed: 20716741]
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Detailed physical examination is essential for evaluation of delirium. Delirium may often be the initial manifestation of serious underlying disease in an older person; thus, astute attention to early localizing signs on physical examination may allow early diagnosis of a precipitating insult. A careful search for evidence of occult infections should be performed, including signs of pneumonia, urinary tract infection, acute abdominal processes, joint infections, or new cardiac murmur. A detailed neurologic examination with attention to focal or lateralizing signs is also crucial.
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Diagnostic and Statistical Manual of Mental Disorders IV-Text Revision (DSM-5)—
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The American Psychiatric Association DSM-5 guidelines were developed based on expert opinion and remain the current standard for definition and diagnostic criteria for delirium.
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Confusion Assessment Method—
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Simple, validated tool currently in widespread use (Table 21–3). It has sensitivity of 94% to 100%, specificity of 90% to 100%, and negative predictive value of 90% to 100% for delirium. It has also been validated in patients with dementia. In the intensive care setting, it is feasible to perform cognitive evaluation and screen for delirium using the CAM-ICU, a modification of the CAM for use in mechanically ventilated, restrained, or nonverbal patients. CAM-ICU has not, however, been found to perform as well, with sensitivity of 64% to 73% and negative predictive value of 83%; among verbal patients, the sensitivity drops to <50%.
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Instruments developed and validated for use in identification of delirium include the Nursing Delirium Screening Scale (NuDesc), Delirium Symptom Interview, NEECHAM Confusion Scale, Delirium Observation Screening Scale, and Intensive Care Delirium Screening Checklist. Instruments developed and validated for use in determining severity of delirium, once it is identified, include the Memorial Delirium Assessment Scale, Clinical Global Impression Scale, and Delirium Severity Index. Other instruments that both diagnose and determine severity of delirium include the Delirium Rating Scale-98 and Cognitive Test for Delirium.