Introduction to delirium

Delirium is an acute deterioration of mental state characterised by fluctuating symptoms of impaired attention, cognition and consciousness, typically developing over hours to days.

There are 3 types of delirium:

  • hyperactive delirium: the patient has agitation, restlessness, hallucinations or delusions
  • hypoactive delirium: the patient is quiet and withdrawn. Hypoactive delirium is the most prevalent form of delirium but is not as obvious and often missed
  • mixed delirium: the patient alternates between hyperactive and hypoactive states.

Delirium can cause the patient and their family, carers or significant others significant distress. In addition, compared to a patient of the same age, a patient with delirium is more likely to:

  • have a longer hospital stay
  • be admitted to a residential aged-care facility
  • have a subsequent dementia diagnosis
  • fall
  • die.

Delirium can be prevented—it is imperative to identify patients at risk of delirium to instigate preventive measures.

One of the key principles of managing delirium is to identify and treat its cause, yet delirium is frequently underdiagnosed. Although, at the time of writing, no trials have been undertaken to determine whether screening for delirium improves outcomes, screening combined with evidence-based prevention strategies, is a pragmatic, reasonable approach. Australian healthcare services are required to undertake cognitive screening in adults with one or more of the following delirium risk factors:

  • age 65 years or older (45 years or older for Aboriginal and Torres Strait Islander peoples)
  • cognitive impairment or dementia
  • a previous episode of delirium
  • severe medical illness
  • current hip fracture.

For further information, see the Australian Commission on Safety and Quality in Health Care (ACSQHC) Delirium Clinical Care Standard.

Delirium has been mostly studied in acute hospital settings including critical care. Although it is unclear whether data from acute hospital settings are relevant to patients in other settings (eg residential aged-care facilities, where the prevalence of delirium is high), it is necessary to extrapolate data to this patient group because research is limited.

Management of children with delirium is beyond the scope of these guidelines—seek expert advice.