Delirium goes by many names, such as acute confusion, metabolic encephalopathy, and acute brain syndrome, which adds to the confusion around diagnosis. Delirium is not a distinct disease state, and it has multiple etiologies. This wide range of symptoms and etiologies leads to difficulties in diagnosis.
The prevalence is variable and appears to be related to severity of illness. Estimates range from 20% to as high as 80% in patients with cancer or acquired immunodeficiency syndrome (AIDS). A recent prospective study found a 47% prevalence rate in inpatients with terminal cancer. The prevalence can be as high as 85% in the final hours before death.
Clinically, presenting symptoms can include the following:
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Restlessness
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Disturbances in the sleep-wake cycle
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Confusion
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Distractibility
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Disorientation to time or place or person
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Illusory experiences (misinterpreting stimuli that is perceived)
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Hallucinations (no external stimuli present) in any perceptual modality, although auditory and visual are the most common
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Delusions
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Disorganized thinking and incoherent or inappropriate speech
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Emotional dysregulation (including lability, contextually inappropriate emotions, inappropriate fear, sadness, anger, irritability, and euphoria)
Neurologic symptoms can include asterixis, tremor, myoclonus, incoordination, and urinary and fecal incontinence.
The presence of delirium adds significantly to morbidity. It can hinder communication with both health professionals and family. As a result, evaluation of other symptoms, especially pain, can be compromised. Family members are distressed that they are not able to communicate with their loved one. Disorientation can lead to dangerous behaviors, such as pulling out lines, trying to get out of bed and falling, or acting aggressively to those in close proximity. It is difficult to understand the wishes of the delirious patient because they can be communicative one moment and nonsensical the next. Given the fluctuating nature of delirium, it is critical to be vigilant regarding the competence of the patient to make decisions around his or her own care and to assess this on a continuous basis. Collateral information from allied health professionals and family is an important element of this appraisal. The continuous assessment of competence is a requirement in delirious states; this is frequently overlooked by health care professionals.
Diagnosis and Assessment
Given the multitude of possible presentations, a structured approach to the diagnosis is most helpful. The diagnostic criteria of the American Psychiatric Association, as stated in the Diagnostic and Statistical Manual of Mental Disorders, revised fourth edition (DSM-IV-TR), narrows the focus to disturbances of consciousness and cognition and emphasizes the fluctuating nature of the illness ( Box 11-1 ). This fluctuating nature is a critical and pathognomonic feature of delirium. Indeed, one of the more common presentations is “sundowning,” in which the symptoms present or worsen near twilight. Therefore, serial assessments at different times of the day are mandatory to ensure accurate diagnosis.
* DSM-IV-TR, American Psychiatric Association, Washington, D.C., 2000.
Depressed mood most of the day, nearly every day
Markedly diminished interest or pleasure in all, or almost all, activities of the day
Significant weight loss or gain
Insomnia or hypersomnia
Psychomotor agitation or retardation
Fatigue or loss of energy
Feelings of worthlessness or excessive or inappropriate guilt
Diminished ability to think or concentrate, or indecisiveness
Recurrent thoughts of death (not just fear of dying), suicidal ideation, suicide attempt, or a specific plan for committing suicide
Assessment tools for delirium and cognitive status are listed in Box 11-2 . They can be used to quantitatively measure changes in cognitive status. Devlin and colleagues reviewed the advantages and disadvantages of various assessment tools for intensive care unit use.
Memorial Delirium Assessment Scale (MDAS)
Confusion Assessment Method (CAM)
Delirium Rating Scale (DRS)
Mini-Mental State Examination (MMSE) 7
Montreal Cognitive Assessment (MOCA) 8
Delirium is classified into two subtypes: hyperactive and hypoactive. In the former, agitation and increased activity is the hallmark. The presence of hallucinations, delusions, and illusions is frequent. In contrast, hypoactive delirium is frequently missed because patients do not present with overt behavioral issues. Instead, they are often lethargic, confused, and have a decreased level of alertness; they are the “quiet” patients. Delirium exists on a continuum from hypoactive to hyperactive; the symptoms may also be mixed. Hypoactive delirium may appear similar to depression. Careful assessment of mood states when the patient is oriented is helpful. If the patient is not able to communicate in a goal-directed fashion, an electroencephalogram (EEG) can help differentiate them. The EEG show diffuse slowing in delirium.
Delirium and dementia can present with similar symptoms. They can be differentiated by careful history taking and review of the chart (if available), looking specifically for the time of onset. Dementia will have a much more insidious onset than the rapid onset of delirium. Dementia itself is a risk factor for delirium; certainly, it is possible to have the acute onset of delirium on a background of chronic cognitive changes of dementia.
Risk Factors
Risk factors include older age (>65), preexisting brain injury, dementia or cognitive impairment, history of delirium, sensory impairment, malnutrition, alcohol or other substance dependence (from withdrawal), cancer, and AIDS.
Etiology
As previously stated, there are multiple causes of delirium, which may act alone or in concert with other etiologies ( Box 11-3 ).
DRUGS
Anticholinergics
Antineoplastic agents
Benzodiazepines
Opiates
Sedative/hypnotics
Steroids
DISEASE STATES
Hepatic encephalopathy
Uremic encephalopathy
Hypoxia
Cardiac failure
INFECTIOUS
Sepsis
Meningitis
Encephalitis
METABOLIC IMBALANCES
Electrolyte balance
Glucose levels
Thyroid imbalance
Parathyroid imbalance
Adrenal imbalance
Pituitary imbalance
Thiamine deficiency
Vitamin B 12 deficiency
Folic acid deficiency
STRUCTURAL
Metastases
Brain lesions
Head trauma (e.g., from falls)
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