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Delirium is a sudden, fluctuating, and usually reversible cognitive disorder characterized by disorientation, the inability to pay attention, the inability to think clearly, and a change in the level of consciousness.

Delirium is an abnormal mental state, not a disease. Although the term has a specific medical definition, it is often used to describe any type of confusion.

Because delirium is a temporary condition, determining how many people have it is difficult. Delirium, which is usually a sign of a newly developed disorder, affects about one third of hospitalized people aged 70 or older.

What Is Confusion? Confusion means different things to different people, but doctors use the term to describe people who cannot process information normally. Confused people cannot follow a conversation answer questions appropriately understand where they are make critical judgments that affect safety remember important facts Confusion has many different causes, including the use of certain drugs (prescription, over-the-counter, and illicit) and a wide variety of disorders. Delirium and dementia, though very different disorders, both cause confusion. When a person is confused, doctors try to determine what the cause is, particularly if it is delirium or dementia. If confusion develops or worsens suddenly, the cause may be delirium. In such cases, medical attention is needed immediately, because delirium may be caused by a serious disorder. Also, treating the cause, once identified, can often reverse the delirium. If confusion develops slowly, the cause may be dementia. Medical attention is needed but not urgently. Treatment may slow the mental decline in people with dementia but cannot restore mental function and usually cannot stop the decline.

Causes

Development or worsening of almost any disorder can cause delirium. Any person can become delirious when they are extremely ill or are taking drugs that affect brain function. However, delirium can result from less severe conditions in older people and in people whose brain has been affected by a stroke, dementia, or other disorders that cause nerve degeneration. In such people, delirium can result from a relatively minor illness, such as retention of urine or feces; sensory deprivation, such as that due to being socially isolated or not wearing glasses or hearing aids; or prolonged sleep deprivation. For example, the sensory and sleep deprivation that occurs in intensive care units (ICUs) may contribute to delirium. This disorder is sometimes called ICU psychosis.

Being in the hospital can also contribute to or trigger delirium. About 10 to 20% of older people develop delirium while they are in the hospital. Delirium is also very common after surgery, probably because of the stress of surgery, the anesthetics used during surgery, and the analgesics used after surgery.

The most common reversible cause of delirium is drugs. Delirium may result from use of a drug or from withdrawal of a drug that has been taken for a long time. In younger people, ingestion of poisons (such as rubbing alcohol or antifreeze), use of illicit drugs, or acute intoxication with alcohol are common causes of delirium. In older people, prescription drugs are usually the cause. Psychoactive drugs, such as opioids (including morphineSome Trade Names
MS CONTIN
ORAMORPH
and meperidineSome Trade Names
DEMEROL
), sedatives (including benzodiazepines), antipsychotics, and antidepressants, impair brain function by their direct effects on nerve cells. Delirium may result. Drugs with anticholinergic effects (see Anticholinergic: What Does It Mean?), including many over-the-counter (OTC) antihistamines, may cause delirium. Amphetamines, which are stimulants, may also cause delirium. Sudden withdrawal of a sedative (such as a benzodiazepine or barbiturate) that has been taken for a long time frequently results in delirium. Delirium commonly occurs in alcoholics who suddenly stop drinking alcohol (see Drug Use and Abuse: Symptoms and Complications) and in heroin users who suddenly stop using heroin.

Abnormal blood levels of electrolytes, such as calcium, sodium, or magnesium, can interfere with the metabolic activity of nerve cells and lead to delirium. Abnormal electrolyte levels may result from use of a diuretic, dehydration, or disorders such as kidney failure and widespread cancer. An underactive thyroid gland (hypothyroidism) causes delirium with lethargy; an overactive thyroid gland (hyperthyroidism) causes delirium with hyperactivity.

In younger people, the cause of delirium is usually a condition that directly affects the brain—for example a brain infection, such as meningitis or encephalitis. In older people, the cause is usually drugs or a disorder that affects other parts of the body—for example, an infection that affects the brain indirectly, such as a urinary tract infection, pneumonia, or influenza.

Symptoms

Delirium usually begins suddenly and progresses over hours or days. The actions of people with delirium vary but roughly resemble those of a person who is becoming progressively more intoxicated.

The hallmark of delirium is an inability to pay attention. People with delirium cannot concentrate, so they have trouble processing new information and cannot recall recent events. Sudden confusion about time and, at least partially, about place (where they are) may be an early sign of delirium. If delirium is severe, people may not know who they are. Thinking is confused, and people with delirium ramble, sometimes becoming incoherent. The level of consciousness may fluctuate between increased wakefulness and drowsiness. Symptoms often change within minutes and tend to worsen late in the day (a phenomenon called sundowning). People with delirium often sleep restlessly or reverse their sleep-wake cycle, sleeping during the day and staying awake at night.

People with delirium may be frightened by bizarre visual hallucinations, seeing things or people that are not there. Some people develop paranoia or have delusions (false beliefs usually involving a misinterpretation of perceptions or experiences).

Personality and mood may change. Some people become so quiet and withdrawn that no one notices that they are delirious. Others become agitated and restless and may pace. People who develop delirium after taking sedatives are likely to become very drowsy and withdrawn. Those who have taken amphetamines or who have stopped taking sedatives may become aggressive and hyperactive.

Delirium can last hours, days, or even longer, depending on the severity and the cause. If the cause of delirium is not quickly identified and treated, the person may become increasingly drowsy and unresponsive, requiring vigorous stimulation to be aroused (a condition called stupor (see Stupor and Coma). Stupor may lead to coma or death. Delirium is often the first sign of another, sometimes serious disorder, especially in older people.

Diagnosis

Mild delirium may be difficult to recognize. Doctors may miss up to 80% of all cases of delirium in hospitalized people.

Most people thought to have delirium are hospitalized for evaluation and protection. Diagnostic procedures can be performed quickly and safely in the hospital, and any disorders detected can be treated quickly.

Because delirium may be caused by a serious disorder (which could be rapidly fatal), doctors try to identify the cause as quickly as possible. Treating the cause, once identified, can often reverse the delirium.

Doctors first try to distinguish delirium from other disorders that affect mental function. Doctors collect as much information about the person's medical history as possible. Friends, family members, or other observers are asked how the confusion began, how quickly it progressed, and what they know about the person's physical and mental health and use of drugs (including alcohol and illicit drugs, especially for younger people). Information may come from medical records, the police, emergency medical personnel, or evidence such as pill bottles and certain documents. Documents such as a checkbook, recent letters, or notification of unpaid bills or missed appointments can indicate a change in mental function. In older people, doctors try to distinguish delirium from dementia by determining how quickly the confusion developed and what the person's usual mental function is. However, distinguishing the two disorders may be difficult, because people who have dementia can also develop delirium. Therefore, doctors usually treat people whose mental function suddenly worsens—even if they have dementia—as if they have delirium until proved otherwise.

If delirium is accompanied by agitation and hallucinations, delusions, or paranoia, it must be distinguished from a psychosis due to a psychiatric disorder, such as manic-depressive illness or schizophrenia. People with a psychosis due to a psychiatric disorder do not have confusion or memory loss, and the level of consciousness does not change. However, if a psychosis begins during old age, it usually results from delirium or dementia. Psychosis due to a psychiatric disorder rarely begins during old age.

Doctors perform a physical examination, which includes a neurologic examination (see Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Introduction). The examination includes blood and urine tests, such as cultures to look for signs of infection. Computed tomography (CT) or magnetic resonance imaging (MRI) may be performed. In younger and some older people, a spinal tap (lumbar puncture (see Diagnosis of Brain, Spinal Cord, and Nerve Disorders:Procedures) may be performed to obtain cerebrospinal fluid for analysis. Such analysis helps doctors rule out infection or bleeding.

Comparing Delirium and Dementia Feature Delirium Dementia Development Sudden Slow Duration Days to weeks Months to years Presence of other disorders or physical problems Almost always present; may be a severe illness, drug use or withdrawal, or a problem with metabolism Possibly none Variation at night Almost always worse Often worse Attention Greatly impaired Maintained until late stages Level of consciousness Fluctuates from lethargy to agitation Normal until late stages Orientation to surroundings Varies Impaired Use of language Slow, often incoherent, and inappropriate Sometimes difficulty finding the right word Memory Jumbled and confused Lost, especially for recent events Mental function Lost, variably and unpredictably Lost, relatively consistently for all functions Cause Usually an acute illness or drugs; in older people, usually infection, dehydration, or drugs Usually Alzheimer's disease, vascular dementia, or Lewy body dementia Need for treatment Emergency medical attention Nonemergency medical attention

Is It Delirium or Psychosis? Common Signs of Delirium Common Signs of Psychosis Due to a Psychiatric Disorder Confusion about current time, date, place, or identity Usually, awareness of time, date, place, and identity Difficulty paying attention Retention of ability to pay attention Loss of recent memory Retention of recent memory Inability to think logically Inability to think logically Inability to perform simple calculations Retention of ability to calculate Preoccupations commonly inconsistent Preoccupations often fixed and consistent Hallucinations (if any) mostly visual or involving touch Hallucinations (if any) mostly auditory Fever or other signs of infection History of previous psychiatric disturbances Evidence of recent drug use Drug use not necessarily involved Tremor Usually, no tremor

Treatment and Prognosis

Most people who have delirium are hospitalized for treatment. However, when the cause of delirium is obvious and can be corrected readily (for example, when the cause is a drug) and when the person has family members who can provide care, a person with delirium may be cared for at home.

Treatment of delirium depends on its cause. For example, doctors treat infections with antibiotics, dehydration with fluids and electrolytes given intravenously, and delirium due to alcohol withdrawal with benzodiazepines (as well as with measures to stop the use of alcohol).

General measures are also important. The environment is kept as quiet and calm as possible. At every opportunity, staff and family members should reassure the person, help orient the person to time and place, and explain procedures and other proceedings. People who have delirium are prone to many problems, including dehydration, malnutrition, incontinence, falls, and bed sores. Preventing such problems requires meticulous care.

Measures may be needed to prevent people who are extremely agitated or who have hallucinations from injuring themselves or their caregivers. For example, family members are encouraged to stay with the person, or the person is put in a room near the nurses' station. However, sometimes during hospitalization, use of padded restraints is necessary—for example, to keep the person from pulling out intravenous lines. Restraints are applied carefully, released at frequent intervals, and discontinued as soon as possible, because they can upset the person and worsen the agitation.

For agitation, drugs are used only after all other measures have been ineffective. For most people who are agitated, the drugs of choice are antipsychotic drugs (see Antipsychotic Drugs), or sedatives, such as benzodiazepines (see Sleep Aids: Not to Be Taken Lightly and Antianxiety Drugs). Sedatives are particularly useful when delirium is due to the sudden withdrawal of alcohol after heavy use for a long time. Doctors are careful when prescribing these drugs, particularly for older people. Drugs may worsen the agitation and confusion and may mask an underlying problem.

Most people recover fully if the condition causing delirium is rapidly identified and treated. Any delay greatly decreases the chance of a full recovery. Even when delirium is treated, some symptoms may persist for many weeks or months, and improvement may occur slowly. In some people, delirium evolves into chronic brain dysfunction similar to dementia.

Hospitalized people who have delirium are up to 10 times more likely to develop complications in the hospital (including death) than those who do not have delirium. Hospitalized people who have delirium, particularly older people, have a longer stay in the hospital, higher treatment costs, and a longer recovery time after they leave the hospital.

Last full review/revision February 2003