What is Delirium?

Delirium is a medical problem which can develop when people are acutely unwell and/or are undergoing medical treatment, such as surgery. Older people, especially those who have dementia, are more at risk of developing delirium at these times. Delirium is also common in people receiving palliative care, and children with fevers or after some anaesthetics. Although the cause is not always known, it is always a consequence of physical changes related to illness or its treatment (e.g. infection, pain, or the addition of medications).

Delirium causes changes to the person’s usual mental functioning. Its onset is rapid (hours or days). It is sometimes confused with other conditions (e.g. stroke, depression and dementia).

Delirium is a serious condition and, if not managed promptly, other complications can occur, such as falls, longer hospital stays and ongoing cognitive impairment. While delirium usually lasts for only a few days and can be reversed, delirium sometimes persists even after the underlying problems are treated.

In children, delirium due to fever usually happens at night, occurs during the early stages of their illness and is usually very brief. At present, little is known about how long delirium will last in children when it occurs due to other circumstances.

‘Acute confusion’ or ‘impaired cognition’ are other terms that might be used to refer to delirium. (1-3)

How might the person’s behaviour change during delirium?

People who have delirium suddenly become confused, forgetful and less able to pay attention to others and their environment. They will have difficulty concentrating, and may be disoriented, easily distracted and unable to engage in conversation. They may also misinterpret situations, show unfamiliar swings in emotion and see, hear, think or believe things that are not real. What they say is often mixed up or makes only partial sense to others. For the person, it feels like being in a strange dream or nightmare. As the person with delirium has trouble understanding, communication will be more difficult than usual and the person may become frustrated or angry with you.

Behaviour can range from restlessness, irritability, combativeness and repetitive behaviours, to uncharacteristic quietness, sleepiness, or withdrawal. These behaviours often fluctuate during the day.

Though behaviour changes are similar in children, irritability, agitation, sleep wake disturbance and changing moods are more common. Like adults, children may experience hallucinations. (2-7)

How common is delirium?

Delirium is a common condition amongst older people in community, residential and acute care settings. Up to one third of older people have delirium when they are admitted to hospital, and from 33% to 92% of older people will develop delirium when they have surgery to repair their hip fracture. Though delirium occurs less often in older people living in the community, it is more common in people aged over 85 years. In residential aged care the rate of delirium can be high, often in association with pre-existing dementia. In Intensive Care Units about 2 out of every 3 patients will get delirium. Although delirium is common in older people and people receiving palliative care, anyone can become delirious when unwell.           

Although children are at risk of delirium, there little research about how common it is. At present,  studies suggest that about 10% of hospitalised children/adolescents and 17-66% of paediatric intensive care patients referred to inpatient psychiatry services suffer delirium.

People who have had delirium are more likely to experience it again. (3, 8-10)



Why do people get delirium?

Delirium is caused by an underlying acute medical/surgical/traumatic condition which requires treatment. Although we are still uncertain about why people get delirium, we do know that people are more at risk when personal factors create vulnerability (e.g. older age, illness and cognitive decline) and other factors or events occur to enhance this vulnerability (e.g. infections, dehydration, medication).

Factors which seem to make children more at risk of delirium include: young age, being male, pre-existing progressive cognitive impairment or intellectual disability, having pre-exisiting behaviour problems and carer anxiety or absence. Common factors that enhance vulnerability include sepsis, anaemia, hypoxia and trauma. Children are thought to be more vulnerable to delirium from fever and general anaesthesia than adults. (3, 11-13)   

How is delirium treated?

Delirium is usually managed by firstly treating the cause. For example, if a urinary tract infection is causing delirium, antibiotics will be commenced; if dehydration is a cause, intravenous fluids may be given.

In addition, the following strategies may be used to help the person during their delirium:

•  Keeping the hospital room as quiet and calm as possible, especially at night.
•   Avoiding placing the person in a room near busy and noisy parts of the ward (e.g. nurses station)
•    Avoiding moving the person from one room to another.
•    Allocating someone to stay with the person.
•   Gently reminding the person where they are, why they are in hospital and what day/time it is.
•   Asking family and other familiar people to visit and sit with the person. For children, to be a constant presence who comforts the child.

If other calming strategies have not helped and the person is very distressed, sometimes medicines may be used for short periods of time to help calm the person.