14th February 2025

Delirium

Overview of delirium

Delirium is an acute confusional state which is common in healthcare settings and associated with worse outcomes. It can cause significant distress to patients and staff.

Patient-related risk factors include age ≥65, underlying dementia or cognitive impairment, visual or hearing impairment, frailty or immobility and current hip fracture. Screening for these risk factors at presentation to an inpatient setting allows at-risk individuals to be identified and monitored for features of delirium.

Modifiable risk factors include unfamiliar surroundings, sensory factors including lack of usual sensory aids, physiological factors (dehydration, constipation, hypoxia, pain, infection) and medical factors (severe illness of any kind, electrolyte imbalance, medications, drug or alcohol withdrawal).

Diagnosis of delirium

To meet DSM (Diagnostic and Statistical Manual of Mental Disorders)-5 criteria for a delirium diagnosis, the patient must show all 4 of the following:

• Attention deficit, e.g. poor concentration, distractible
• Cognitive deficit, e.g. memory, language, disorientation OR abnormal perceptions, e.g. hallucinations
• Acute timeline (i.e. hours or days) to develop, from their usual baseline
• Features suggesting a physiological cause, as discerned by history, examination and/or laboratory tests

The following additional features are also commonly present:

• Altered consciousness: drowsy or heightened arousal
• Altered physiological processes: altered sleep, appetite and mobility
• Behavioural change: agitation, aggression, altered communication, withdrawal
• Fluctuant nature: symptoms vary throughout the day

Delirium can be divided into clinical subtypes based on a comparison to the patient’s baseline:

• Hyperactive: increased arousal, agitation and aggression
• Hypoactive: lethargic, withdrawn, inactive or incoherent
• Mixed delirium includes features of both hyperactive and hypoactive delirium

Investigations in delirium

Brief cognitive assessments such as the 4AT or short Confusion Assessment Method (CAM) can be used to support the diagnosis, although abnormal results are not specific to delirium, and differentiating delirium from dementia (or delirium-on-dementia) can be challenging. A collateral history is particularly crucial, and also more specific tests such as the Observational Scale of Level of Arousal (over 80% specific).

After a diagnosis of delirium is made, further investigation is needed for any underlying cause. There is a wide differential diagnosis for confusion, which can be found in the Dementia section (see Presentation and diagnosis of dementia). Although an acute condition is more likely in delirium, long-term comorbidities and medications should also be reviewed.

General blood tests (including bone profile, TFTs, B12, folate) and a septic screen are usually performed. CT brain and ECG should be considered. Context-specific investigations may include:

• Drug levels for patients on digoxin, lithium or quinidine
• LP or EEG if suspecting meningitis, seizure activity or encephalopathy
• Urine drug screen

Management of delirium

Management is generally supportive. Any contributing factors should be addressed, including alcohol or drug withdrawal. Medications should be reviewed, as some may worsen delirium, e.g. sedatives, opioids, antidepressants, steroids, stimulants, anti-Parkinson drugs or anticholinergics.

If it is unclear whether the diagnosis is delirium or dementia, treatment for delirium should be initiated first. If symptoms are ongoing, risk factors should be reviewed and a diagnosis of dementia considered.

Patients with delirium may have significant distress and pose a risk to themselves or others, in which case management should be escalated as follows:

• Start conservative: verbal and non-verbal communication with the aim of de-escalation
• If necessary and safe, use pharmacological measures: low-dose haloperidol, titrated up as necessary. Antipsychotic drugs should ideally be avoided in patients with Parkinson’s disease or Lewy body dementia

References

• National Institute for Health and Care Excellence. Delirium: prevention, diagnosis and management [Internet]. NICE. 2010 [cited 2022 Mar 1]. Available from: https://www.nice.org.uk/guidance/CG103
• Pisani M, Dosa DM. Assessment of delirium [Internet]. BMJ Best Practice. 2021 [cited 2022 Mar 1]. Available from: https://bestpractice.bmj.com/topics/en-gb/241