📋 Key Information Summary
- Delirium is an acute disturbance of attention and awareness with a fluctuating course, often triggered by illness, medications, pain, infection, or hospitalisation — it is a medical emergency, not a psychiatric diagnosis.
- Prevalence in Australian hospitalised older adults is 18–35%; incidence may reach 50% in ICU settings. Up to two-thirds of cases go unrecognised by admitting teams.
- The 4AT (score ≥ 4) is the recommended rapid bedside screening tool in Australian hospitals; the Confusion Assessment Method (CAM) confirms the diagnosis when administered by trained clinicians.
- Three motor subtypes exist: hyperactive (agitated, hallucinating — most visible), hypoactive (quiet, withdrawn — most common and most missed), and mixed (fluctuates between both).
- Hypoactive delirium accounts for 30–60% of all cases and is independently associated with worse outcomes than the hyperactive subtype due to diagnostic delay.
- Always search for the underlying precipitant — use the mnemonic DIM-HOPE: Drugs, Infection, Metabolic, Hypoxia, Other pain, Post-operative, Environment.
- Polypharmacy (≥ 5 medications), anticholinergic burden, benzodiazepines, opioids, and antipsychotics are the most common iatrogenic causes — conduct a structured medication review on every patient.
- Non-pharmacological prevention bundles (HELP protocol components) reduce delirium incidence by 30–40% and are first-line management: orientation, sleep hygiene, early mobilisation, hydration, hearing/vision optimisation, and pain control.
- Avoid physical restraints — they prolong delirium and increase falls, injury, and mortality. Use 1:1 nursing observation and environmental modification instead.
- Pharmacological treatment is reserved for severe agitation posing safety risk: low-dose haloperidol (0.5–1 mg PO/IM) is first-line; avoid benzodiazepines except in alcohol/benzodiazepine withdrawal.
- Delirium is an independent predictor of mortality (OR 1.9–3.2), prolonged hospital stay, accelerated cognitive decline, and increased risk of subsequent dementia and institutionalisation.
- Aboriginal and Torres Strait Islander peoples have a higher burden of delirium precipitants (infection, renal disease, diabetes) and face barriers to screening due to cultural and language factors — culturally safe, validated tools must be used.
Introduction & Australian Epidemiology
Delirium is a serious neuropsychiatric syndrome characterised by an acute disturbance in attention, awareness, and cognition that develops over hours to days, represents a change from baseline, and tends to fluctuate in severity during the course of the day. It is a medical emergency — not a psychiatric disorder, and not an inevitable consequence of ageing — that demands prompt identification, systematic investigation of underlying causes, and targeted management.
Delirium is the most common surgical complication in older adults and one of the most frequent reasons for geriatric medicine consultation in Australian hospitals. Despite its frequency, it remains profoundly under-recognised; prospective studies consistently demonstrate that clinicians miss 60–70% of cases, with hypoactive delirium being the most frequently overlooked subtype.
Australian Epidemiological Data
- Prevalence on admission: 10–30% of older adults (≥ 65 years) presenting to Australian emergency departments have delirium at the time of assessment.
- In-hospital incidence: An additional 10–20% develop delirium during their admission (incident delirium), yielding a combined burden of 18–35% of older inpatients at any given time.
- ICU settings: Up to 50% of mechanically ventilated patients and 20–40% of non-ventilated ICU patients develop delirium in Australian intensive care units.
- Post-operative: Incidence of post-operative delirium ranges from 15–53% after hip fracture repair and 10–25% after elective cardiac surgery.
- Residential aged care: Delirium is identified in 30–40% of residents transferred from aged care facilities to emergency departments, yet it is documented as a diagnosis in fewer than one-quarter of these presentations.
- Cost to the Australian health system: Delirium-related admissions are estimated to cost AUD 4.0–4.8 billion per annum when accounting for prolonged bed days, rehabilitation, and residential aged care placement.
- Risk factors amplified in Australia: High rates of polypharmacy, chronic kidney disease, diabetes mellitus, respiratory disease, and alcohol-related harm in both general and Aboriginal and Torres Strait Islander populations contribute to a particularly high delirium burden.
The Australian Commission on Safety and Quality in Health Care (ACSQHC) includes delirium in its Sepsis Clinical Care Standard and the Comprehensive Care Standard (NSQHS), mandating that hospitals implement systematic screening, assessment, and prevention strategies for at-risk patients.
Prognosis and Long-Term Outcomes
Delirium is not a transient inconvenience. It is independently associated with:
- Increased 12-month mortality (odds ratio 1.9–3.2)
- Accelerated cognitive decline and new-onset dementia
- Increased risk of permanent residential aged care placement
- Functional decline at 6 and 12 months post-discharge
- Post-traumatic stress disorder in patients and carers
Diagnosis and Screening Tools
Timely diagnosis of delirium requires both a high index of clinical suspicion and the use of validated screening and diagnostic instruments. The DSM-5 criteria remain the diagnostic gold standard, but bedside tools are essential for routine clinical practice.
DSM-5 Diagnostic Criteria for Delirium
All four criteria (A–D) must be met:
- A — Disturbance in attention and awareness: Reduced ability to direct, focus, sustain, and shift attention.
- B — Acute onset and fluctuating course: Develops over hours to days; severity tends to fluctuate during the day.
- C — Additional cognitive disturbance: Memory deficit, disorientation, language disturbance, visuospatial or perceptual disturbance.
- D — Not better explained by a pre-existing condition: Does not occur in the context of a severely reduced level of arousal (coma) and is not attributable to another neurocognitive disorder without a superimposed acute change.
Recommended Screening Tools in Australian Practice
| Tool | Time to Administer | Sensitivity / Specificity | Best Use Context | Australian Recommendation |
|---|---|---|---|---|
| 4AT | < 2 minutes | Sens 76–90% / Spec 65–92% | Rapid bedside screening by any clinician (nurse, doctor, allied health); no training required | Recommended first-line screening tool for all Australian hospitals |
| CAM (Confusion Assessment Method) | 5–10 minutes | Sens 94–100% / Spec 90–95% | Diagnostic confirmation by trained clinician after positive screen | Gold standard for confirmation; training package available via ACSQHC |
| CAM-ICU | 2–5 minutes | Sens 80–95% / Spec 89–100% | ICU patients, including mechanically ventilated and non-verbal patients | Standard tool in Australian ICUs; mandated by many ICU protocols |
| 3D-CAM | 3 minutes | Sens 95% / Spec 94% | Structured interview for ward patients; combines cognitive testing with CAM features | Useful for research and quality improvement projects |
| SQiD (Single Question in Delirium) | < 30 seconds | Sens 75–80% / Spec 70–75% | Ultra-rapid screen; ask carer: "Is [patient] more confused than usual?" | Useful as initial triage in busy ED and aged care settings |
| DRS-R-98 (Delirium Rating Scale — Revised) | 10–20 minutes | Sens 91–100% / Spec 85–95% | Severity rating, monitoring trajectory, and research | Useful for delirium liaison services and follow-up monitoring |
The 4AT — Recommended Australian Screening Tool
The 4AT is a freely available, rapid delirium tool that requires no specialist training, making it ideal for routine use by any clinician across emergency departments, medical and surgical wards, and aged care settings. A score of ≥ 4 suggests possible delirium and mandates further clinical assessment.
| 4AT Item | Assessment | Score |
|---|---|---|
| 1. Alertness | Normal alertness → 0; Mildly sleepy, wakes to voice → 0; Clearly abnormal alertness → 4 | 0 or 4 |
| 2. AMT4 (Abbreviated Mental Test – 4 questions) | Age, date of birth, current year, current place — each correct answer = 0; each error = 1 | 0–4 |
| 3. Attention | Months of the year backwards (Jan–Dec) or serial 7s — no errors = 0; ≥ 2 errors or unable = 1; unable to understand or cooperate = 2 | 0–2 |
| 4. Acute change or fluctuating course | Evidence of acute change or fluctuation in mental status, attention, or cognition over prior 2 weeks — No = 0; Yes = 4 | 0 or 4 |
Essential Components of the Delirium Workup
Once delirium is identified, the following structured assessment should be undertaken to identify the precipitant:
- Detailed history — from family/carer regarding baseline cognition, functional status, symptom onset and course, recent medication changes, and behavioural observations.
- Medication review — complete reconciliation with attention to anticholinergic burden, benzodiazepines, opioids, corticosteroids, antipsychotics, anticonvulsants, and any new agents.
- Focused physical examination — vital signs (including temperature, oxygen saturation), hydration status, neurological examination, skin (infection, pressure injury), respiratory (pneumonia), and abdominal examination (constipation, urinary retention).
- Pain assessment — use self-report scales where possible or behavioural pain scales (e.g., PAINAD for dementia) — uncontrolled pain is one of the most common and reversible precipitants.
- Cognitive assessment — document baseline cognitive status and compare with current state; obtain collateral history from carers and residential aged care facilities.
Investigations
Medicare Benefits Schedule (MBS): General pathology items (FBC: 65070, U&E: 66503, LFTs: 66512, CRP: 65095, TSH: 66719) are bulk-billed under standard arrangements. CT brain (MBS item 56001) and EEG (MBS item 11005) require specialist referral or are available through public hospital services without out-of-pocket cost.
Hyperactive, Hypoactive and Mixed Delirium
Delirium is classified into three motor subtypes based on the patient's level of psychomotor activity. Recognising the subtype is clinically important because it influences diagnostic approach, treatment strategy, and prognosis.
Distinguishing Delirium from Other Conditions
| Feature | Delirium | Dementia | Depression | Psychosis |
|---|---|---|---|---|
| Onset | Acute (hours–days) | Insidious (months–years) | Weeks–months | Variable (days–weeks) |
| Course | Fluctuating, often worse at night | Progressive, relatively stable within a day | Persistent, diurnal variation | Sustained, may escalate |
| Attention | Markedly impaired | Relatively preserved until late stages | Often preserved | Variable |
| Consciousness | Clouded, altered | Clear | Clear | Clear |
| Orientation | Impaired | Impaired (gradual) | Usually intact | Usually intact |
| Perceptual disturbance | Visual hallucinations common | Rare until late | Rare | Auditory hallucinations more common |
| Reversibility | Usually reversible with treatment of cause | Irreversible (though can fluctuate with superimposed delirium) | Treatable | Treatable |
Common Precipitants and Causes
Delirium is almost always multifactorial. The search for precipitants must be systematic and exhaustive. In Australian clinical practice, use the mnemonic DIM-HOPE to ensure no major cause is overlooked. Most cases have 2–4 contributing factors; identifying and reversing all of them is the key to management.
DIM-HOPE Mnemonic
| Category | Common Causes |
|---|---|
| D — Drugs | Anticholinergics (promethazine, oxybutynin, tricyclic antidepressants, antihistamines), benzodiazepines, opioids, corticosteroids, antipsychotics, polypharmacy (≥ 5 medications), medication withdrawal (alcohol, benzodiazepines, SSRIs) |
| I — Infection | Urinary tract infection, pneumonia (aspiration and community-acquired), cellulitis/soft tissue infection, sepsis, COVID-19, intra-abdominal infection, meningitis/encephalitis |
| M — Metabolic | Dehydration/hypovolaemia, hypoglycaemia, hyperglycaemia, hyponatraemia, hypernatraemia, hepatic encephalopathy, uraemia, hypercalcaemia, hypothyroidism/hyperthyroidism, Wernicke encephalopathy |
| H — Hypoxia | Pneumonia, pulmonary embolism, heart failure/acute pulmonary oedema, COPD exacerbation, acute coronary syndrome, anaemia (Hb < 80 g/L) |
| O — Other | Constipation, urinary retention, acute urinary obstruction, sensory deprivation (hearing aid not working, glasses not available), immobility, sleep deprivation |
| P — Pain | Uncontrolled acute pain (post-operative, fracture, ischaemic), chronic pain flare, undertreated pain in non-verbal patients |
| E — Environment | ICU environment, excessive noise, room changes, absence of natural light, lack of orientation cues, loss of familiar objects, isolation, physical restraints |
High-Risk Medications in Australian Practice
Special Causes — Don't Miss These
- Alcohol withdrawal delirium (delirium tremens): Onset 48–96 hours after last drink; hyperactive subtype; requires benzodiazepine therapy (CIWA-Ar protocol), IV thiamine, electrolyte correction, and ICU monitoring. Mortality 5–15% if untreated.
- Wernicke encephalopathy: Triad of confusion, oculomotor dysfunction, and ataxia (all three present in only ~16%); treat with IV thiamine 300–500 mg TDS for 3–5 days — do NOT give glucose before thiamine.
- Posterior reversible encephalopathy syndrome (PRES): Hypertension, seizures, visual disturbance, confusion — associated with immunosuppressants, eclampsia, and renal failure.
- Non-convulsive status epilepticus: Persistent altered consciousness without overt seizures; requires EEG for diagnosis; consider in refractory cases.
- Meningitis/encephalitis: Fever, neck stiffness, photophobia — perform lumbar puncture; do not delay empirical antibiotics (ceftriaxone + vancomycin ± dexamethasone) if suspected.
Prevention and Non-Pharmacological Management
Prevention is the most effective strategy for delirium. Non-pharmacological multicomponent intervention bundles reduce delirium incidence by 30–40% (NNT 6–8) and are recommended as first-line management for all hospitalised older adults. These strategies are also the foundation of treatment once delirium has developed.
Core Non-Pharmacological Strategies (HELP Protocol Components)
Pharmacological Management — When Non-Pharmacological Measures Are Insufficient
Pharmacological intervention is reserved for patients with severe agitation or distress that poses a risk to the safety of the patient or others, and only after non-pharmacological measures have been optimised and reversible causes have been addressed. There is no evidence that antipsychotics reduce delirium duration, severity, or mortality — they are used purely for symptom management of dangerous agitation.
What NOT to Do
- Do not use benzodiazepines for delirium (except alcohol/benzodiazepine withdrawal) — they worsen confusion, increase fall risk, and prolong delirium duration.
- Do not use physical restraints — they increase agitation, injury, duration of delirium, and mortality.
- Do not use antipsychotics for hypoactive delirium — there is no evidence of benefit and risk of harm.
- Do not leave delirium untreated — "it will resolve on its own" is a dangerous assumption; untreated delirium carries significant morbidity and mortality.
- Do not assume delirium is dementia — always seek and treat reversible precipitants, even in patients with known dementia.
Special Populations
Pregnancy
Risk factors: Pre-eclampsia/eclampsia (Hypertensive disorders of pregnancy), post-partum haemorrhage, amniotic fluid embolism, HELLP syndrome, sepsis, and magnesium toxicity in labour.
Considerations: Delirium in pregnancy requires urgent exclusion of eclampsia and metabolic emergencies. Antiemetics with anticholinergic properties (promethazine, hyoscine) used for hyperemesis may contribute.
Pharmacological management: Haloperidol (Category B3) is generally preferred over benzodiazepines if pharmacological intervention is required. Avoid olanzapine and quetiapine in pregnancy due to limited safety data. Always involve obstetric and psychiatric teams.
Paediatrics
Prevalence: Delirium occurs in 20–30% of paediatric ICU admissions; under-recognised in children, especially the hypoactive subtype.
Screening: The Pediatric Confusion Assessment Method for the ICU (pCAM-ICU) is validated for children ≥ 5 years; the Cornell Assessment of Pediatric Delirium (CAPD) is validated for all ages including infants.
Common causes: Post-surgical (especially cardiac), infection, medication effects (opioids, benzodiazepines, anticholinergics), metabolic derangement, sleep disruption in PICU.
Management: Non-pharmacological strategies (reunification with parents/caregivers, sleep promotion, familiar objects, age-appropriate communication, minimising invasive devices) are the mainstay. If pharmacological intervention is required, consult paediatric psychiatry or intensivist — avoid antipsychotics without specialist guidance. Melatonin (1–3 mg PO nocte, Not PBS listed) may assist with sleep–wake cycle restoration.
Older Adults and Frailty
Key risk factors: Age ≥ 65, pre-existing cognitive impairment or dementia, sensory impairment (hearing, vision), polypharmacy, functional dependence, malnutrition, dehydration, and frailty.
Unique considerations: Atypical presentation (may present with quiet withdrawal rather than agitation). Lower drug clearance. Increased susceptibility to anticholinergic effects. Higher risk of falls with any sedative medication.
Medication adjustments: Start antipsychotics at half the adult dose (haloperidol 0.25–0.5 mg). Avoid long-acting benzodiazepines (diazepam, nitrazepam). Use the Anticholinergic Cognitive Burden Scale for all medication reviews. Cease unnecessary medications using deprescribing frameworks (e.g., STOPP/START criteria).
Renal Impairment
Relevance: Acute kidney injury and uraemia are common delirium precipitants. Uraemic toxins, electrolyte disturbances (hyperkalaemia, hypernatraemia, hypocalcaemia), and metabolic acidosis all contribute to encephalopathy.
Medication considerations: Reduce haloperidol dose in severe renal impairment (eGFR < 15 mL/min). Avoid morphine (active metabolite M6G accumulates; use fentanyl or hydromorphone instead). Dose-adjust gabapentin, pregabalin, and lithium. Ensure adequate dialysis clearance if patient is on renal replacement therapy.
Hepatic Impairment
Relevance: Hepatic encephalopathy may mimic or precipitate delirium. Impaired drug metabolism prolongs the half-life of benzodiazepines, opioids, and antipsychotics.
Medication considerations: Avoid benzodiazepines entirely (precipitate/worsen hepatic encephalopathy via impaired clearance of GABAergic metabolites). Haloperidol and olanzapine undergo extensive hepatic metabolism — use with extreme caution, reduce dose, and monitor LFTs. Lactulose and rifaximin are the treatments of choice for hepatic encephalopathy. Screen for spontaneous bacterial peritonitis as a precipitant.
Immunocompromised Patients
Relevance: Higher risk of opportunistic infections (CMV, HSV encephalitis, cryptococcal meningitis, cerebral toxoplasmosis) as delirium precipitants. Corticosteroid-induced delirium is common in transplant and oncology patients.
Considerations: Lower threshold for advanced neuroimaging (CT with contrast, MRI brain) and lumbar puncture. Blood cultures and CSF analysis (including viral PCR, cryptococcal antigen, India ink) should be performed early. Antimicrobial and antiviral regimens should be guided by immunological status — consult infectious diseases. Tacrolimus and cyclosporine levels should be checked (neurotoxicity).
Aboriginal and Torres Strait Islander Australians experience a disproportionate burden of delirium precipitants and face unique barriers to screening, diagnosis, and culturally safe care. Recognition and management of delirium in this population require culturally informed approaches developed in partnership with communities and Aboriginal and Torres Strait Islander health practitioners.
Higher Burden of Delirium Precipitants
- Infection: Significantly higher rates of rheumatic heart disease (endocarditis), chronic suppurative otitis media (meningitis risk), skin and soft tissue infections, respiratory infections, and urinary tract infections.
- Renal disease: Aboriginal and Torres Strait Islander Australians have 4–6 times the rate of end-stage kidney disease compared with non-Indigenous Australians; uraemic encephalopathy is a significant precipitant.
- Diabetes: Prevalence of type 2 diabetes is 3–4 times higher; hyperglycaemia and diabetic ketoacidosis contribute to delirium.
- Alcohol-related harm: Higher rates of alcohol use disorder contribute to alcohol withdrawal delirium (delirium tremens) and Wernicke–Korsakoff syndrome, particularly in remote communities where access to acute withdrawal management is limited.
- Ear and hearing: Chronic suppurative otitis media affects up to 30% of children and many adults in remote communities, leading to conductive hearing loss — a major barrier to delirium screening and communication.
Barriers to Delirium Recognition
Culturally Safe Approaches to Prevention and Care
- Involve Aboriginal and Torres Strait Islander health practitioners in all stages of delirium assessment, communication with families, and care planning.
- Engage Aboriginal liaison officers (ALOs) and family members to provide orientation, cultural support, and familiar presence at the bedside — this is a powerful non-pharmacological intervention.
- Respect cultural practices: Allow family to stay at the bedside (including overnight), support connection to country and cultural activities where possible, and accommodate sorry business.
- Use validated, culturally appropriate assessment tools: The Kimberley Indigenous Cognitive Assessment (KICA) is a validated cognitive screen for Aboriginal Australians in remote areas and may help distinguish delirium from dementia.
- Address hearing loss proactively: Provide amplification devices, engage interpreter services where English is not the first language, and adapt communication strategies.
- Ensure timely investigation and treatment of infection: In remote settings, lower thresholds for empirical antibiotics and transfer to higher-level care when infection-related delirium is suspected.
- Close the Gap in preventable hospital admissions: Addressing chronic disease burden (diabetes, renal disease, rheumatic heart disease, alcohol-related harm) through primary health care and community-led programs is the most effective long-term strategy to reduce delirium incidence in Aboriginal and Torres Strait Islander communities.
📚 References
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