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Delirium is
an acute, transient, usually reversible, fluctuating disturbance
in attention, cognition, and consciousness level. Causes include almost
any disorder, intoxication, or drug. Diagnosis is clinical, with
laboratory and usually imaging tests to identify the cause. Treatment is
correction of the cause and supportive measures.
Delirium may occur at any age but is more common among the elderly. At least 10% of elderly patients who are admitted to the hospital have delirium; 15 to 50% experience delirium at some time during hospitalization. Delirium is also common among nursing home residents. When delirium occurs in younger people, it is usually due to drug use or a life-threatening systemic disorder. Delirium is sometimes called acute confusional state or toxic or metabolic encephalopathy.
Etiology
The most common causes are the following:
Many other conditions can cause delirium (see Table 2: Delirium and Dementia: Causes of Delirium ). In about 10 to 20% of patients, no cause is identified.
Predisposing factors include brain disorders (eg, dementia, stroke, Parkinson's disease), advanced age, sensory impairment, and multiple coexisting disorders. Precipitating factors include use of drugs (particularly ≥ 3 new drugs), infection, dehydration, immobility, undernutrition, and use of bladder catheters. Recent exposure to anesthesia also increases risk, especially if exposure is prolonged and if anticholinergics are given during surgery. Decreased sensory stimuli at night may trigger delirium in at-risk patients. For elderly patients in an ICU, risk of delirium (ICU psychosis) is particularly high.
Pathophysiology
Mechanisms are not fully understood but may involve reversible impairment of cerebral oxidative metabolism, multiple neurotransmitter abnormalities, and generation of cytokines. Stress of any kind upregulates sympathetic tone and downregulates parasympathetic tone, impairing cholinergic function and thus contributing to delirium. The elderly are particularly vulnerable to reduced cholinergic transmission, increasing their risk of delirium. Regardless of cause, the cerebral hemispheres or arousal mechanisms of the thalamus and brain stem reticular-activating system become impaired.
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Table 2
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Causes of Delirium
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Category
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Examples
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Cerebrovascular disorders
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Ischemic stroke, hemorrhagic stroke
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Drugs
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Anticholinergics, antiemetics, antihistamines (eg, diphenhydramine ), antihypertensives, antipsychotics, antispasmodics, benzodiazepines, cimetidine , corticosteroids, digoxin , hypnotics, levodopa, muscle relaxants, opioids, recreational drugs, sedatives, tricyclic antidepressants
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Endocrine disorders
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Hyperparathyroidism, hyperthyroidism, hypothyroidism
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Hematologic disorders
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Hyperviscosity syndrome, leukemic blast cell crisis, polycythemia, thrombocytosis
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Infections
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Encephalitis, fever, meningitis, pneumonia, sepsis, systemic infections, UTIs
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Injuries
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Burns, electrical injuries, fat embolism, heatstroke, hypothermia
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Metabolic disorders
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Acid-base disturbances, fluid and electrolyte abnormalities, hepatic or uremic encephalopathy, hyperosmolality, hyperglycemia, hyperthermia, hypoglycemia, hypoxia, Wernicke's encephalopathy
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Neurologic disorders
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Nonconvulsive status epilepticus (rare), postictal state, transient ischemia
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Structural disorders
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Brain abscesses, primary or metastatic brain tumors, subdural hematomas
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Vascular or circulatory disorders
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Anemia, cardiac arrhythmias, heart failure, hypoperfusion states, shock
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Vitamin deficiency
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Thiamin deficiency, vitamin B12 deficiency
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Withdrawal syndromes
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Alcohol, barbiturates, benzodiazepines, opioids
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Other causes
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Change of environment, fecal impaction, hypertensive encephalopathy, long stays in ICU, mental disorders, postoperative states, sensory deprivation, sleep deprivation, toxins that affect the CNS, urinary retention
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Symptoms and Signs
Delirium is characterized primarily by difficulty focusing, maintaining, or shifting attention (inattention). Consciousness level fluctuates; patients are disoriented to time and sometimes place or person. They may have hallucinations. Confusion regarding day-to-day events and daily routines is common, as are changes in personality and affect. Thinking becomes disorganized, and speech is often disordered, with prominent slurring, rapidity, neologisms, aphasic errors, or chaotic patterns.
Symptoms fluctuate over minutes to hours; they may lessen during the day and worsen at night.
Symptoms may include inappropriate behavior, fearfulness, and paranoia. Patients may become irritable, agitated, hyperactive, and hyperalert, or they may become quiet, withdrawn, and lethargic. Very elderly people with delirium tend to become quiet and withdrawn—changes that may be mistaken for depression. Some patients alternate between the two. Usually, patterns of sleeping and eating are grossly distorted. Because of the many cognitive disturbances, insight is poor, and judgment is impaired. Other symptoms and signs depend on the cause.
Diagnosis
Delirium, particularly in elderly patients, is often overlooked by clinicians. Clinicians should consider delirium in any elderly patient who presents with impairment in memory or attention.
Mental
status examination:
Patients with any sign of cognitive impairment require a formal mental status examination (see Sidebar 1: Approach to the Neurologic Patient: Examination of Mental Status ). Attention is assessed first. Simple tests include immediate repetition of the names of 3 objects, digit span (ability to repeat 7 digits forward and 5 backward), and naming the days of the week forward and backward. Inattention (patient does not register directions or other information) must be distinguished from poor short-term memory (patient registers information but rapidly forgets it). Further cognitive testing is futile for patients who cannot register information.
After initial assessment, standard diagnostic criteria, such as the Diagnostic
and Statistical Manual of Mental Disorders (DSM) or Confusion Assessment Method (CAM) may be used. The following features are required for diagnosis:
plus one of the following:
or
History:
History is obtained by interviewing family members, caregivers, and friends. It can determine whether the change in mental status is recent and is distinct from any baseline dementia (see Table 1: Delirium and Dementia: Differences Between Delirium and Dementia*). The history helps distinguish a mental disorder from delirium. Mental disorders, unlike delirium, almost never cause inattention or fluctuating consciousness, and onset of mental disorders is nearly always subacute. Sundowning (behavioral deterioration during evening hours), which is common among institutionalized patients with dementia, may be difficult to differentiate; newly symptomatic deterioration should be presumed to be delirium until proved otherwise.
History should also include use of alcohol and illicit, OTC, and prescription drugs, focusing particularly on drugs with CNS effects and on new additions, discontinuations, or changes in dose, including overdosing.
Physical examination:
Examination, particularly in patients who are not fully cooperative, should focus on the following:
Findings can suggest a cause. For example, fever, meningismus, or Kernig and Brudzinski signs suggest CNS infection. Tremor and myoclonus suggest uremia, liver failure, drug intoxication, or certain electrolyte disorders (eg, hypocalcemia, hypomagnesemia). Ophthalmoplegia and ataxia suggest Wernicke-Korsakoff syndrome (see Drug Use and Dependence: Diagnosis, Prognosis, and Treatment). Focal neurologic abnormalities (eg, cranial nerve palsies, motor or sensory deficits) or papilledema suggests a structural CNS disorder. Lesions, swelling, and other findings suggest head trauma.
Testing:
Testing usually includes CT or MRI, tests for suspected infections (eg, CBC, blood cultures, chest x-ray, urinalysis), and measurement of electrolytes, BUN, creatinine, plasma glucose, and levels of any drugs suspected to be having toxic effects.
If the diagnosis is unclear, further testing may include pulse oximetry (or ABGs); liver function tests; measurement of serum calcium and albumin, thyroid-stimulating hormone (TSH), vitamin B12, ESR, and antinuclear antibody (ANA); and a test for syphilis (eg, rapid plasma reagin [RPR] or Venereal Disease Research Laboratory [VDRL] test).
If the diagnosis is still unclear, testing may include CSF analysis (particularly to rule out meningitis, encephalitis, or subarachnoid hemorrhage), measurement of serum ammonia, and testing to check for heavy metals.
If nonconvulsive status epilepticus, a rare cause, is suspected (based on history, subtle motor twitches, automatisms, or presence of a steadier but less intense pattern of bewilderment and drowsiness), EEG should be done.
Prognosis
Morbidity and mortality rates are higher in patients who have delirium when they are hospitalized or who develop delirium during hospitalization.
Delirium due to certain conditions (eg, hypoglycemia, intoxication, infection, iatrogenic factors, drug toxicity, electrolyte imbalance) typically resolves rapidly with treatment. However, recovery may be slow (days to even weeks or months), especially in the elderly, resulting in longer hospital stays, increased risk and severity of complications, increased costs, and long-term disability. Some patients never fully recover from delirium. For up to 2 yr after delirium occurs, risk of cognitive and functional decline, institutionalization, and death is increased.
Treatment
Correcting the cause (eg, treating infection, giving fluids and electrolytes for dehydration) and removing aggravating factors (eg, stopping drugs) may result in resolution of delirium. Nutritional deficiencies (eg, of thiamin or vitamin B12) should be corrected, and good nutrition and hydration should be provided.
General measures:
The environment should be stable, quiet, and well-lit and include visual cues to orient the patient (eg, calendar, clocks, family photographs). Frequent reorientation and reassurance by hospital staff or family members may also help. Sensory deficits should be minimized (eg, by replacing hearing-aid batteries, by encouraging patients who need eyeglasses or hearing aids to use them).
Approach to treatment should be interdisciplinary (with a physician, physical and occupational therapists, nurses, and social workers); it should involve strategies to enhance mobility and range of motion, treat pain and discomfort, prevent skin breakdown, ameliorate incontinence, and minimize risk of aspiration.
Agitation may threaten the well-being of the patient, a caregiver, or a staff member. Simplifying drug regimens and avoiding use of IV lines, bladder catheters, and physical restraints (particularly in the long-term care setting) as much as possible can help prevent exacerbation of agitation and reduce risk of injury. However, in certain circumstances, physical restraints may be needed to prevent patients from harming themselves or others. Restraints should be applied by a staff member trained in their use; they should be released at least every 2 h to prevent injury and discontinued as soon as possible. Use of hospital-employed assistants (sitters) as constant observers may help avoid the need for restraints.
Explaining the nature of delirium to family members can help them cope. They should be told that delirium is usually reversible but that cognitive deficits often take weeks or months to abate after resolution of the acute illness.
Drugs:
Drugs, typically low-dose haloperidol (0.5 to 1.0 mg po, IV, or IM once, then repeated q 1 to 2 h as needed), may lessen agitation or psychotic symptoms; occasionally, much higher doses are necessary. However, drugs do not correct the underlying problem and may prolong or exacerbate delirium. Second-generation (atypical) antipsychotics (eg, risperidone 0.5 to 3 mg po q 12 h, olanzapine 2.5 to 15 mg po once/day) may be used instead because they have fewer extrapyramidal adverse effects; however, long-term use in patients with dementia may increase risk of stroke and death. These drugs are not typically given IV or IM.
Benzodiazepines (eg, lorazepam 0.5 to 1.0 mg po or IV once, then repeated q 1 to 2 h as needed) have a more rapid onset of action (5 min after parenteral administration) than antipsychotics but commonly worsen confusion and sedation in patients with delirium.
Overall, antipsychotics and benzodiazepines are equally effective for managing agitation in delirium, but antipsychotics have fewer adverse effects. Benzodiazepines are preferred for delirium attributed to sedative withdrawal and for patients intolerant of antipsychotics (eg, those with Parkinson's disease or Lewy body dementia). Dose of these drugs should be reduced as quickly as possible.
Prevention
Because delirium greatly worsens prognosis for hospitalized patients, prevention should be emphasized. Hospital staff members should be trained to take measures to maintain orientation, mobility, and cognition and to ensure sleep, good nutrition and hydration, and sufficient pain relief, particularly in elderly patients. Family members can be encouraged to help with these strategies. The number and doses of drugs should be reduced if possible.
Last full review/revision August 2007 by Alexander Auchus, MD
Content last modified August 2007
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