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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Delirium = acute onset, fluctuating course, inattention, and altered level of consciousness — caused by an underlying medical condition
- Three subtypes: hyperactive (agitation), hypoactive (drowsy, withdrawn — most common and most commonly MISSED), and mixed
- Identify and TREAT the underlying cause — delirium is a symptom, not a diagnosis: infection (UTI, pneumonia), medications, constipation, pain, urinary retention, metabolic disturbance
- First-line management is NON-PHARMACOLOGICAL: reorientation, lighting, familiar objects, hydration, mobilisation
- Low-dose haloperidol or lorazepam ONLY for severe agitation causing harm — use lowest dose for shortest time
Overview
Delirium is an acute, fluctuating disturbance of attention, awareness, and cognition resulting from an underlying physiological cause. It is not a disease but a clinical syndrome indicating acute brain dysfunction. Delirium is classified as hyperactive (agitation, restlessness, hallucinations), hypoactive (drowsiness, withdrawal, reduced activity — often missed), or mixed. It is extremely common in hospitalised older adults and is associated with increased mortality, longer hospital stays, institutional care, and accelerated cognitive decline. Pre-existing dementia is the strongest predisposing factor.
Epidemiology
Delirium affects 20–30% of medical inpatients and up to 50% of surgical patients over 65 years. Prevalence is even higher in ICU (up to 80%). Predisposing factors include advanced age (>65 years), pre-existing cognitive impairment/dementia (strongest risk factor), frailty, sensory impairment (visual, hearing), polypharmacy, alcohol dependence, and severe illness. Precipitating factors include infection, medications (opioids, benzodiazepines, anticholinergics), metabolic disturbance (hyponatraemia, hypercalcaemia, uraemia), pain, constipation, urinary retention, surgery, dehydration, and hypoxia.
Clinical Features
Symptoms
Acute onset (hours-days) — a change from baseline
Fluctuating course — symptoms wax and wane throughout the day (often worse at night — "sundowning")
Inattention — difficulty focusing, easily distracted, cannot follow conversation or serial tasks
Disorganised thinking — rambling, incoherent speech, tangential responses
Altered level of consciousness — hyperalert (hyperactive) or drowsy/obtunded (hypoactive)
Perceptual disturbances: hallucinations (typically visual), illusions, paranoid delusions
Sleep-wake cycle disturbance
Hyperactive: agitation, aggression, pulling at lines/catheters, wandering
Hypoactive: drowsy, withdrawn, quiet, reduced oral intake — MOST COMMONLY MISSED subtype
Signs
Inattention: cannot recite months of the year backwards or serial 7s
Disorientation to time, place, person
Fluctuating GCS or conscious level
Signs of underlying cause: fever (infection), tachycardia, tachypnoea, signs of urinary retention, abdominal distension (constipation)
Investigations
First-line
Delirium screening toolConfusion Assessment Method (CAM): acute onset + fluctuating + inattention + EITHER disorganised thinking OR altered consciousness = positive. 4AT is an alternative bedside screen
Identify underlying causeBloods: FBC, CRP, U&Es, calcium, glucose, LFTs, TFTs, B12. Urinalysis and MSU. Blood cultures if febrile. Blood gas if hypoxia suspected
Chest X-rayScreen for pneumonia if respiratory symptoms or pyrexia
ECGIf cardiac cause suspected, or before starting haloperidol (QTc prolongation)
Second-line
CT headIf head injury, focal neurology, reduced GCS, or no obvious precipitant — exclude subdural haematoma, stroke, intracranial infection
Medication reviewCRITICAL — identify and stop deliriogenic drugs: opioids, benzodiazepines, anticholinergics, corticosteroids, antihistamines, dopamine agonists
Specialist
Lumbar punctureIf meningitis or encephalitis suspected (fever + headache + confusion)
EEGIf non-convulsive status epilepticus suspected — diffuse slowing in delirium
1
Treat the underlying cause
- Treat infection: antibiotics if indicated
- Stop or reduce deliriogenic medications: opioids, benzodiazepines, anticholinergics
- Correct metabolic disturbance: dehydration, electrolyte imbalance, hypoglycaemia, hypoxia
- Relieve pain, constipation, urinary retention
2
Non-pharmacological management (first-line)
- Reorientation: clock, calendar, familiar objects, consistent staff, explain environment
- Ensure adequate lighting (especially at night — nightlight to reduce misperception)
- Ensure glasses and hearing aids are available and used
- Promote sleep hygiene: reduce noise, minimise night-time observations if safe
- Encourage mobilisation and adequate hydration/nutrition
- Avoid unnecessary catheterisation, IV lines, and physical restraints
- Involve family/carers — familiar faces reduce disorientation
3
Pharmacological (ONLY if severe agitation causing harm)
- Haloperidol 0.5–1 mg PO/IM as a single dose — lowest effective dose, shortest duration
- Avoid in Lewy body dementia and Parkinson disease — extreme antipsychotic sensitivity (use lorazepam instead)
- Lorazepam 0.5–1 mg PO/IM: alternative if haloperidol contraindicated or in alcohol withdrawal delirium
- Do NOT use antipsychotics to sedate — only to manage distress and safety risk
4
Prevention (NICE CG103)
- Screen at-risk patients (>65, cognitive impairment, hip fracture, severe illness)
- Multi-component interventions: orientation, hydration, mobilisation, sleep promotion, medication review, sensory aids
- NICE recommends against prophylactic antipsychotics for delirium prevention
Complications
- Increased mortality: Delirium is associated with 2–4× increased mortality — reflects severity of underlying illness
- Prolonged hospital stay: Average increase of ~8 days
- Falls and injury: Agitation, disorientation — fall risk assessment essential
- Accelerated cognitive decline: Delirium accelerates progression to dementia, even in previously cognitively intact individuals
- Institutional care: Higher rates of discharge to care homes
- Psychological distress: Frightening hallucinations and confusion — patients and families may need support post-episode
UKMLA Exam Tips
- 1Delirium vs dementia: delirium = ACUTE onset, FLUCTUATING, INATTENTION, altered consciousness. Dementia = chronic, progressive, stable attention
- 2Hypoactive delirium is the MOST COMMON subtype and MOST COMMONLY MISSED — always screen
- 3CAM criteria: acute onset + fluctuating + inattention + (disorganised thinking OR altered consciousness)
- 4ALWAYS look for the underlying cause — delirium is a SYMPTOM: infection, medications, metabolic, pain, retention, constipation
- 5Non-pharmacological management is FIRST-LINE — not haloperidol
- 6Haloperidol is CONTRAINDICATED in Lewy body dementia and Parkinson disease (use lorazepam)
- 7Pre-existing dementia is the strongest predisposing factor for delirium — but delirium ON TOP OF dementia is still delirium
practicetest your knowledge on deliriumApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — neurology and beyond.
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