Key Facts

Delirium is a medical emergency requiring urgent identification and treatment of the underlying cause. Prevention is more effective than treatment.

Epidemiology

• Affects 20-30% of medical inpatients >65; up to 50% post-operatively
• Hypoactive delirium accounts for 50-70% and is frequently unrecognised
• Incidence increases with age, frailty, and cognitive impairment

Aetiology

PINCH ME mnemonic:

• Pain
• Infection (UTI, pneumonia, cellulitis)
• Nutrition (dehydration, electrolyte disturbance)
• Constipation / urinary retention
• Hydration (dehydration, fluid overload)
• Medication (opioids, anticholinergics, benzodiazepines, steroids, drug/alcohol withdrawal)
• Environment (unfamiliar surroundings, sleep deprivation, immobility)

Pathophysiology

• Multifactorial model: predisposing vulnerability + precipitating insult
• Neuroinflammation: systemic inflammation → microglial activation → neurotransmitter imbalance
• Cholinergic deficiency and dopaminergic excess are central to the pathophysiology
• Disruption of the ascending reticular activating system
• Blood-brain barrier dysfunction during acute illness

Core Features

• Acute onset (hours to days)
• Fluctuating course (lucid intervals)
• Inattention (key feature — cannot sustain attention)
• Altered level of consciousness
• Cognitive disturbance (disorientation, memory impairment)
• Perceptual disturbance (hallucinations, illusions)
• Psychomotor disturbance (agitation or withdrawal)
• Sleep-wake cycle disturbance

Subtypes

• Hyperactive: agitation, restlessness, hallucinations, aggression (25%)
• Hypoactive: withdrawal, drowsiness, reduced movement, quiet confusion (50-70%) — worst prognosis, often missed
• Mixed: alternating between hyperactive and hypoactive (25%)

Red Flags

• Sudden onset confusion in previously well/stable patient
• New agitation or aggression in a patient with dementia
• Reduced consciousness level (GCS drop)
• Fever with confusion (sepsis)
• Head injury with confusion (intracranial pathology)
• Post-operative confusion (common; always investigate)

Bedside

• 4AT screening tool: ≥4 = probable delirium (alertness, AMT4, attention, acute change)
• Observations: temperature, HR, BP, O2 sats, RR, blood glucose
• Urinalysis (UTI)
• ECG
• Pain assessment
• Medication chart review

Bloods

• FBC, CRP (infection)
• U&Es (dehydration, AKI, electrolyte disturbance)
• LFTs, calcium, magnesium, phosphate
• Blood glucose, HbA1c
• TFTs
• Blood cultures (if pyrexial)
• B12, folate (if nutritional deficiency suspected)

Imaging

• CXR (pneumonia)
• CT head: if head injury, focal neurology, no clear cause identified, anticoagulated
• CT abdomen/pelvis: if intra-abdominal cause suspected

Special Tests

• MSU (urine culture)
• Confusion Assessment Method (CAM): research gold standard
• EEG: if non-convulsive status suspected (diffuse slowing in delirium)
• Lumbar puncture: if meningitis/encephalitis suspected

Non-pharmacological (FIRST LINE)

• Identify and treat underlying cause (treat infection, stop offending drugs, correct dehydration, relieve pain/constipation/retention)
• Reorientation: clocks, calendars, familiar objects, consistent staff
• Ensure sensory aids (glasses, hearing aids)
• Promote sleep-wake cycle: natural light, reduce nocturnal interventions
• Mobilise early: avoid unnecessary catheterisation and restraint
• Involve family/carers
• Avoid unnecessary ward moves
• Delirium prevention: NICE CG103 recommends multicomponent intervention for all at-risk patients

Pharmacological

• Only if patient at risk of harm to self or others, and non-pharmacological measures have failed
• Haloperidol 0.5mg PO/IM (start low, max 2mg/24h in elderly); avoid in Parkinson's/Lewy body dementia
• Lorazepam 0.5-1mg PO/IM: preferred in Parkinson's/Lewy body, alcohol withdrawal, seizure risk
• Olanzapine 2.5-5mg: alternative if haloperidol contraindicated
• Review and stop offending medications: opioids, anticholinergics, benzodiazepines, steroids
• Treat underlying causes: antibiotics for infection, IV fluids for dehydration, analgesia for pain

Surgical/Interventional

• Address surgical causes: urinary retention (catheterise), constipation (enemas), fracture fixation

Referral Criteria

• Persistent delirium (>2 weeks): consider psychiatric/geriatric review
• Delirium superimposed on dementia: specialist assessment
• Complex cases: liaison psychiatry

• In-hospital mortality: 10-26% (2× higher than non-delirious patients)
• 1-year mortality: 30-40% (delirium is an independent predictor of death)
• Mean excess hospital stay: 7-10 days
• 30-50% develop dementia within 2-3 years of a delirium episode
• Full recovery in approximately 50%; persistent cognitive impairment in many
• Hypoactive delirium has worst prognosis (often undiagnosed)
• Prevention reduces delirium incidence by 30-40% (multicomponent interventions)

4AT Rapid Clinical Test for Delirium

PINCH ME — Causes of Delirium