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What is delirium?

Delirium is an acute change in mental state. It is characterised by a disturbance of consciousness, attention, cognition and perception that develops over a short period of time (usually hours to a few days). Delirium is a serious medical condition and should be treated as a medical emergency.


Clinical standards of care have been developed for delirium aiming to support the delivery of appropriate care, reduce unwarranted variation in care and promote shared decision making between patients, carers and clinicians.


While delirium can occur in people of any age, older people with a cognitive impairment, such as dementia, are at greater risk. About 10 per cent to 18 per cent of Australians aged 65 years or older have delirium at the time of admission to hospital.


The incidence of delirium is higher in certain hospital settings with up to 50 per cent of patients following heart or hip surgery and 80 per cent or more in adult intensive care units - regardless of age. Patients planning an elective surgical procedure are advised to discuss with their surgeon the risk of developing a delirium.


The early identification of patients at risk of delirium is important so interventions can be put in place to reduce the risk of the delirium developing.


Delirium has been divided into three types.

Hypoactive delirium: This is the most common type of delirium. The patients are quiet and may appear drowsy, withdrawn, lethargic and sleep a lot during the day. 60 per cent of deliriums present in this way as hypoactive.


Hyperactive delirium: This type of delirium is the most easily recognised. Patients can be agitated, restless and have hallucinations.  Only 20 per cent of deliriums present as hyperactive.‚Äč


Mixed delirium: This is a combination of hypoactive delirium and hyperactive delirium and the patient may change between the two states during the day.


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About one in five older people admitted to hospital will experience delirium at some stage of their care.