Delirium (Acute Confusional State)

What delirium is

Delirium is an acute disturbance of brain function. The core feature is inattention: the person cannot focus, follow a conversation or keep track of a simple task. Thinking becomes disorganized, and awareness of time and place slips. It comes on quickly, over hours or a few days, and it fluctuates, so someone may seem nearly normal in the morning and badly confused by evening.

Doctors describe three forms:

• Hyperactive delirium: restless, agitated, pulling at drips, shouting, seeing things that are not there. This is the type people recognize.
• Hypoactive delirium: quiet, withdrawn, sleepy, slow to respond. It is common in older people and is often missed or mistaken for depression or tiredness.
• Mixed delirium: swings between the two.

Delirium symptoms

• Trouble paying attention, easily distracted, losing the thread mid-sentence
• Disorientation: not knowing where they are, or the day or time
• Rambling or illogical speech
• Seeing or hearing things that are not there, or fixed false beliefs, often frightening (for example that staff are trying to harm them)
• Reversed sleep pattern: awake and agitated at night, drowsy by day
• Mood changes: fear, irritability, tearfulness or apathy
• New problems with short-term memory

Family members are often the first to notice. A simple "she is not herself" from someone who knows the person well is an important warning sign. See our page on sudden and gradual confusion for other causes of muddled thinking.

Delirium vs dementia

The two often occur together, which is why the difference matters. Dementia makes a person more vulnerable to delirium, and an episode of delirium can unmask or speed up dementia.

What causes delirium

Delirium usually results from a vulnerable brain meeting one or more triggers. In a frail person with Alzheimer's disease, a mild urine infection can be enough. In a healthy young adult, it takes a severe illness.

Risk factors

• Age over 65
• Dementia or other memory problems
• Poor eyesight or hearing
• Severe illness, hip fracture, or major surgery (especially heart and hip surgery)
• Previous delirium
• Heavy alcohol use

Common triggers

• Infections: urinary tract infections, pneumonia, skin infections, and sepsis.
• Medicines: opioids, benzodiazepines, sleeping pills, antihistamines such as diphenhydramine, bladder medicines with anticholinergic effects, steroids, and starting or stopping several drugs at once.
• Withdrawal: from alcohol, which can progress to delirium tremens, or from benzodiazepines.
• Metabolic problems: dehydration, low or high sodium, low or high blood sugar, kidney or liver failure, low oxygen.
• Brain causes: stroke, head injury, seizures, meningitis.
• Physical stressors: uncontrolled pain, constipation, urinary retention, a catheter, sleep loss, and restraints.
• Surgery and intensive care: postoperative delirium usually appears 1 to 3 days after the operation. ICU delirium affects a large share of ventilated patients.

How delirium is diagnosed

Delirium is a clinical diagnosis. There is no single blood test or scan for it.

1. Bedside screening: tools such as the 4AT or the Confusion Assessment Method (CAM) check alertness, orientation, and attention (for example saying the months of the year backward).
2. History from family: what the person is normally like, when the change began, any new medicines, alcohol use and falls.
3. Examination: temperature, oxygen level, signs of infection, a full bladder, constipation, dehydration and neurological signs.
4. Tests for the cause: blood count, sodium, kidney and liver tests, glucose, calcium, urine test, chest X-ray, and often an ECG. A CT brain scan is done after a fall or head injury, with new neurological signs, or in people on blood thinners. A lumbar puncture or EEG is used occasionally.

A positive urine dipstick alone in an older person is not proof that a UTI caused the delirium. Doctors look for urinary symptoms or fever before blaming the bladder.

Delirium treatment

Treat the cause

Treating infections, correcting fluids and salts, stopping or reducing unnecessary medicines, treating pain, relieving constipation or retention, and managing alcohol withdrawal are the main treatment.

Supportive care that helps

• A calm, well-lit room by day and a dark, quiet room at night
• Glasses and hearing aids in use
• A visible clock and calendar, and frequent gentle reorientation
• Familiar faces: family visits and help with meals
• Getting out of bed and walking as soon as it is safe
• Enough to drink and eat
• Avoiding room moves, physical restraints and unnecessary catheters

Medicines

There is no medicine that cures delirium. Antipsychotics are used short term only when someone is a danger to themselves or others, or is severely distressed, and at the lowest dose. Benzodiazepines can make most delirium worse, except in alcohol or benzodiazepine withdrawal, where they are the treatment.

How long does delirium last?

Most episodes improve within a few days to a week once the cause is treated. In older adults, and especially in people with dementia, symptoms can persist for weeks or months. Some people never fully return to their previous level of thinking. Delirium is linked with a higher risk of falls, pressure sores, longer hospital stays, moving into a care home, faster cognitive decline and death, which is why it is treated as urgent.

Many people remember frightening hallucinations afterward. Talking about the experience helps. After an ICU stay, ongoing memory, mood and physical problems may be part of post-intensive care syndrome.

Preventing delirium

Up to a third of hospital delirium can be prevented with simple measures:

• Bring glasses, hearing aids and dentures to the hospital
• Keep the person drinking, eating and moving
• Ask the care team to review sedating and anticholinergic medicines
• Keep normal sleep patterns: avoid daytime naps and night-time disturbance where possible
• Treat pain well, since untreated pain is a trigger
• Family visits, conversation and familiar objects

If you are a caregiver, tell staff if the person has had delirium before. That alone raises their risk.

Frequently asked questions

What is the most common cause of delirium?

In older adults the commonest triggers are infections (urinary and chest), medicines with sedating or anticholinergic effects, dehydration and surgery. Often several factors combine. In younger adults, alcohol or drug withdrawal and severe illness are more typical. Doctors search for every contributing cause rather than stopping at the first one found.

Is delirium the same as dementia?

No. Delirium comes on suddenly, fluctuates and centers on poor attention. It is usually caused by an illness or drug and often reverses. Dementia develops slowly over months or years and is permanent. The two often overlap, and people with dementia are much more likely to develop delirium.

How long does delirium last in the elderly?

Typically days to a couple of weeks after the cause is treated. In frail older adults and those with dementia, confusion can linger for weeks or months. A minority do not return fully to their previous level, so follow-up with a primary care doctor after discharge is worthwhile.

Can delirium be cured?

Delirium itself has no specific cure, but it usually resolves when the underlying problem is treated. Correcting infection, dehydration, medicine side effects or withdrawal, combined with calm, supportive care, is what brings recovery.

What does hypoactive delirium look like?

The person becomes quiet, drowsy, slow to answer and withdrawn, and may stop eating or drinking. Because they are not disruptive, it is easily mistaken for tiredness or depression. It is just as serious as the agitated form and often signals a more severe illness.

Can young people get delirium?

Yes. Severe infections, high fevers, intensive care, head injury, drug intoxication, and alcohol or drug withdrawal can cause delirium at any age. Children with high fevers can also become briefly delirious. It is simply more common and more easily triggered in older people.