Lucan · Conditions

Delirium

Australian guidance: ANZSGM Position Statement on Delirium + eTG

1. Definition and epidemiology

Delirium is an acute neuropsychiatric syndrome characterised by disturbances in consciousness, attention, cognition, and perception that develop over hours to days and typically fluctuate throughout the day. It is the most common hospital-acquired complication tracked by the Australian Commission on Safety and Quality in Health Care (ACSQHC), with an incidence of 35.7 per 10,000 admissions in Australia in 2019-20. Approximately 10 to 18% of Australians aged 65 years or older have delirium at the time of hospital admission, with a further 2 to 8% developing it during their stay; rates reach 30% or more following cardiac or orthopaedic surgery and 50% or more in adult intensive care units regardless of patient age.

2. Pathophysiology

The precise mechanism of delirium remains incompletely understood but reflects a final common pathway of diffuse cortical and subcortical dysfunction arising from an interaction between predisposing vulnerabilities and acute precipitants. The leading hypothesis centres on cholinergic deficiency combined with dopaminergic excess, disrupting the balance of neurotransmitter systems that regulate arousal, attention, and cognition. Neuroinflammation plays a major role: systemic insults such as infection, surgery, and ischaemia trigger cytokine cascades that impair the blood-brain barrier, activate microglia, and disrupt synaptic transmission (Robbins Ch 28). Metabolic derangements including hypoxia, hypo- or hypernatraemia, uraemia, and hepatic encephalopathy amplify this neurochemical disruption. Structural vulnerability from underlying dementia, cerebrovascular disease, or age-related cortical atrophy reduces the threshold at which any acute insult precipitates delirium. The resulting syndrome involves widespread electroencephalographic slowing and loss of the normal corticothalamic rhythms that underpin sustained attention.

3. Clinical presentation and diagnostic criteria

Delirium presents across three psychomotor subtypes. Hyperactive delirium features agitation, restlessness, combativeness, hallucinations, and delusions. Hypoactive delirium, which is more common in older people and carries a worse prognosis, presents with withdrawal, somnolence, reduced responsiveness, and attentional impairment that is often mistaken for depression or fatigue. Mixed delirium fluctuates between the two. All subtypes share the DSM-5 core diagnostic criteria: (1) disturbance in attention and awareness; (2) acute onset with fluctuating course; (3) an additional disturbance in cognition such as disorientation, language, or perceptual disturbance; and (4) the disturbance is not better explained by a pre-existing neurocognitive disorder, and evidence from history or investigation indicates a direct physiological cause. Key examination findings include inattention on serial subtraction or digit span, waxing and waning alertness, visual hallucinations, sleep-wake cycle reversal, and disorientation to time and place.

4. Investigations and AU-specific cutoffs

Investigation is guided by the clinical history and physical examination aimed at identifying the precipitating cause. First-line investigations include full blood count (FBC), electrolytes, urea and creatinine (UEC), liver function tests (LFTs), blood glucose level (BGL), thyroid-stimulating hormone (TSH), C-reactive protein (CRP), blood cultures if febrile, urinalysis and midstream urine culture, chest X-ray, and electrocardiogram (ECG). In the Australian context, the ACSQHC recommends that any patient aged 65 years or older (or 45 years or older for Aboriginal and Torres Strait Islander people) presenting to hospital with risk factors be screened for cognitive impairment using a validated tool within 24 hours of presentation. The 4AT Assessment Test for Delirium and Cognitive Impairment is validated for both screening and diagnosis and is available in 17 languages; the Confusion Assessment Method (CAM) and its ICU variant (CAM-ICU) are validated diagnostic tools requiring trained administration. CT brain is indicated where there is focal neurology, new seizure, head trauma, or diagnostic uncertainty. Lumbar puncture is reserved for suspected central nervous system infection. Medication review is mandatory: anticholinergic drug burden, opioids, benzodiazepines, and polypharmacy are common reversible contributors.

5. Management

Management of delirium rests on three concurrent priorities: treat the underlying cause, apply multicomponent non-pharmacological strategies, and prevent complications. The ACSQHC Delirium Clinical Care Standard (2021) establishes that non-drug strategies are the mainstay of care and recommends that antipsychotic medicines are not routinely prescribed to treat delirium. Non-pharmacological interventions with the strongest evidence base include frequent reorientation with clocks, calendars, and familiar objects; correction of sensory impairment by ensuring hearing aids and glasses are in place; early mobilisation at least once or twice daily; optimisation of hydration and nutrition; sleep-wake cycle preservation using non-pharmacological sleep hygiene measures; minimising ward moves and unnecessary catheterisations; involving family and carers in care; and medication reconciliation at each care transition. Underlying causes are addressed through a comprehensive multidisciplinary assessment incorporating the GP or specialist summary, medication review, pain assessment, and targeted treatment of identified precipitants such as infection, urinary retention, constipation, hypoxia, or electrolyte disturbance. When an agitated patient poses an imminent risk of harm to themselves or others and non-drug strategies have failed, short-term use of a low-dose antipsychotic at the lowest effective dose for the shortest duration may be considered after discussion with the patient and family, with criteria for cessation documented. On discharge, a comprehensive individualised care plan must be provided to the patient, their family or carer, and their general practitioner within 48 hours.

6. Pharmacology and AU PBS notes

The ACSQHC standard reflects eTG Psychotropic guidance in stating that antipsychotic medicines are not recommended for routine management of delirium. Where short-term use is judged necessary for imminent risk of harm, the options most commonly referenced in Australian practice include:

• Haloperidol (oral or IM): historically the most studied agent; typical starting dose 0.5 to 1 mg in older adults; lowest effective dose for shortest duration. No specific PBS streamlined authority for delirium; use is off-label in this context.
• Olanzapine (oral or IM): second-generation alternative; starting dose 2.5 mg in older adults; higher sedation and metabolic risk profile.
• Quetiapine (oral): may be preferred in patients with Parkinson disease or Lewy body dementia over haloperidol, though all antipsychotics carry elevated risk in this population and should be used with extreme caution or avoided.

Benzodiazepines are to be avoided in delirium management outside the specific context of alcohol or sedative withdrawal (delirium tremens, which falls outside the scope of the ACSQHC standard), as long-acting benzodiazepines worsen and prolong delirium. Avoid anticholinergic drugs, antihistamines, and sedating medications in at-risk patients wherever possible.

7. Complications and monitoring

Patients with delirium should be assessed and monitored daily for the following complications, as specified in the ACSQHC standard:

• Functional decline: encourage mobility and self-care; involve physiotherapy.
• Falls and fall-related injury: reorientation, appropriate lighting, eyeglasses and hearing aids in place, low-rise beds where available.
• Pressure injuries: regular repositioning, skin inspection, pressure-relieving mattresses.
• Dehydration and malnutrition: daily fluid balance, dietitian review for those at nutritional risk.
• Aspiration pneumonia: upright positioning during meals, safe swallowing assessment.
• Longer-term cognitive sequelae: delirium superimposed on dementia carries a worse trajectory for long-term cognition; follow-up cognitive assessment at 10 days post-discharge is recommended. Delirium is a risk factor for subsequent development of dementia in those without a prior diagnosis.

Readmission for delirium within 10 days of discharge is a monitored quality indicator under the ACSQHC standard (Indicator 8b), and the discharge care plan should explicitly include strategies to reduce recurrence.

Written for Australian practice and grounded in the guidance named above. Study material only — not medical advice. Always check against current guidelines.