Делірій

The most common causes of delirium are the following:

• Drugs, particularly anticholinergics, psychoactive drugs or medications, and opioids

• Dehydration

• Infection

Many other conditions can cause delirium (see table Causes of Delirium). In about 10 to 20% of patients, no cause is identified.

Predisposing factors include brain disorders (eg, dementia, stroke, Parkinson disease), advanced age, sensory impairment (eg, impaired vision or hearing), alcohol intoxication, and multiple coexisting disorders.

Precipitating factors include use of drugs (particularly ≥ 3 new medications), infection, dehydration, shock, hypoxia, anemia, immobility, undernutrition, use of bladder catheters (whether urinary retention is present or not), hospitalization, pain, sleep deprivation, and emotional stress. Unrecognized liver or kidney failure may cause medication toxicity and delirium by impairing the metabolism and reducing the clearance of a previously well-tolerated medication.

Delirium can be a common presenting symptom in older patients with a viral disease. For example, coronavirus disease 2019 (COVID-19) can often cause delirium without other typical symptoms or signs of COVID-19. Delirium is more likely to result in poor hospital outcomes (eg, need for ICU care) and death in patients with COVID-19 (1).

Recent exposure to anesthesia also increases risk, especially if exposure is prolonged and if anticholinergics are given during surgery. After surgery, pain and the use of opioid analgesics can also contribute to delirium. Decreased sensory stimuli at night may trigger delirium in at-risk patients.

For older patients in an ICU, risk of delirium (ICU psychosis) is particularly high. Nonconvulsive status epilepticus is an underrecognized cause of altered mental status in ICU patients that should be considered.

Mechanisms are not fully understood but may involve

• Reversible impairment of cerebral oxidative metabolism

• Multiple neurotransmitter abnormalities, especially cholinergic deficiency

• Generation of inflammatory markers, including C-reactive protein, interleukin-1 beta and 6, and tumor necrosis factor–alpha

Stress of any kind upregulates sympathetic tone and downregulates parasympathetic tone, impairing cholinergic function and thus contributing to delirium. Older people are particularly vulnerable to reduced cholinergic transmission, increasing their risk of delirium.

Regardless of the cause, the cerebral hemispheres or arousal mechanisms of the thalamus and brain stem reticular activating system become impaired.

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, delusions, and paranoia. 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 of delirium fluctuate over minutes to hours; they may lessen during the day and worsen at night.

Other symptoms may include inappropriate behavior, fearfulness, and paranoia. Patients may become irritable, agitated, hyperactive, and hyperalert, or, conversely, they may become quiet, withdrawn, and lethargic. Very old 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.

• Mental status examination

• Standard diagnostic criteria to confirm delirium

• Thorough history

• Directed physical examination and selective testing to determine cause

Delirium, particularly in older patients, is often overlooked by clinicians. Clinicians should consider delirium (and dementia) in any older patient who presents with impairment in memory or attention.

• Correction of the cause and removal of aggravating factors

• Supportive care

• Management of agitation

Correcting the cause (eg, treating infection, giving fluids and electrolytes for dehydration) and removing aggravating factors (eg, stopping medications or 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.

Morbidity and mortality rates are high in patients who have delirium and are admitted to the hospital or who develop delirium during hospitalization; 35 to 40% of hospitalized patients with delirium die within 1 year. These rates may be high partly because such patients tend to be older and to have other serious disorders.

Delirium due to certain conditions (eg, hypoglycemia, drug or alcohol intoxication, infection, iatrogenic factors, medication toxicity, electrolyte imbalance) typically resolves rapidly with treatment. However, recovery may be slow (days to even weeks or months), especially in older patients, 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 years after delirium occurs, risk of cognitive and functional decline, institutionalization, and death is increased. In a meta-analysis, delirium in surgical and nonsurgical patients was significantly associated with cognitive impairment lasting ≥ 3 months after the delirium episode (1).

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 older patients. Family members can be encouraged to help with these strategies.

The number and doses of medications should be reduced if possible.

Delirium is more common among older people. About 15 to 50% of older patients experience delirium at some time during a hospital stay. For older patients in an ICU, risk of delirium (ICU psychosis) is particularly high.

Stress of any kind impairs cholinergic function, thus contributing to delirium. Older people are particularly vulnerable to reduced cholinergic transmission, increasing their risk of delirium. Anticholinergic medications can contribute.

Delirium is often the first sign of another, sometimes serious disorder in older people.

Causes of delirium in older people often include less severe conditions:

• Dehydration

• A nonneurologic disorder (eg, urinary tract infection, influenza, thiamin deficiency, vitamin B12 deficiency)

• Pain

• Urinary retention or severe constipation

• Sensory deprivation

• Sleep deprivation

• Stress (any type)

• Use of a bladder catheter

Certain age-related changes make older people more susceptible to developing delirium:

• An increased sensitivity to drugs (particularly sedatives, anticholinergics, and antihistamines)

• Changes in the brain (eg, atrophy, lower levels of acetylcholine)

• The presence of conditions that increase the risk of delirium (eg, stroke, dementia, Parkinson disease, other neurodegenerative disorders, polypharmacy, dehydrations, undernutrition, immobility)

The most obvious symptom of delirium, confusion, may be harder to recognize in older people. Younger people with delirium may be agitated, but very old people tend to become quiet and withdrawn—changes that may be mistaken for depression. In such cases, recognizing delirium is even harder.

If a psychosis develops in an older person, it usually indicates delirium or dementia. Psychosis due to a psychiatric disorder rarely begins during old age.

Delirium can be a common presenting symptom in older patients with viral diseases. For example, COVID-19 may manifest as delirium without other typical symptoms or signs of COVID-19. Delirium is also associated with poor hospital outcomes (eg, need for ICU care) and death in patients with COVID-19 (1).

Memory impairment and inattention may also be the initial symptoms of delirium in older people.

In older people, delirium tends to last longer, and recovery may be slow (days to even weeks or months), resulting in longer hospital stays, increased risk and severity of complications, increased costs, and long-term disability. Some patients never fully recover from delirium.

Because older patients are more likely to have dementia, delirium is often overlooked by clinicians. Clinicians should consider delirium in any older patient who presents with impairment in memory or attention.

Treatment of delirium managed by an interdisciplinary team with multi-faceted measures can benefit older patients because delirium and the hospitalization it usually requires can result in iatrogenic problems (eg, undernutrition, dehydration, pressure ulcers). These problems may have serious consequences in older patients.