Delirium
Description
- Acute, fluctuating disturbance of attention and awareness with disorganised thinking, caused by a medical condition, drug or withdrawal
- *A medical emergency and a symptom, not a diagnosis* - the question is always "delirium due to what?"
Subtypes
| % | Features | Problem | |
|---|---|---|---|
| Hypoactive | ~50% | Withdrawn, drowsy, slow, quiet | *Most missed; worst prognosis*; mistaken for depression or "just tired" |
| Hyperactive | ~25% | Agitated, restless, hallucinating, wandering | Recognised because it is disruptive |
| Mixed | ~25% | Alternates |
Core features
- Inattention - the cardinal feature; cannot sustain, focus or shift attention
- Acute onset (hours-days) and fluctuation - worse in the evening (sundowning), lucid intervals
- Altered conscious level, disorganised thinking, disorientation
- Perceptual disturbance - visual hallucinations, illusions, persecutory delusions
- Sleep-wake cycle reversal
- Emotional lability, autonomic arousal
Epidemiology
- ~20-30% of all older medical inpatients; up to 50% after hip fracture; 50-80% in ICU
- ~30-50% of hospital delirium is preventable - the basis for multicomponent prevention programmes
- Missed or misdiagnosed in up to 2/3 of cases
- Dementia is the single strongest risk factor - present in ~2/3 of delirious inpatients
Aetiopathogenesis
Two-hit model: predisposing vulnerability + precipitating insult
- A frail 90-year-old with dementia delirifies from a UTI; a fit 40-year-old needs septic shock
Predisposing (the vulnerable brain)
- Dementia or prior cognitive impairment (strongest), age >65, previous delirium
- Sensory impairment - hearing and vision
- Frailty, immobility, malnutrition, dehydration
- Multimorbidity, polypharmacy, CKD, liver disease, depression
- Alcohol excess
Precipitating - think PINCH ME + drugs
- Pain (including untreated or unrecognised pain)
- Infection - urinary, chest, skin, intra-abdominal
- Nutrition, Constipation, deHydration
- Medication, Environment
- Urinary retention and faecal impaction - examine for both, every time
- Metabolic - Na+, Ca2+, glucose, uraemia, hepatic failure, hypoxia, hypercapnia, thyroid
- Neurological - stroke, seizure/post-ictal, subdural, encephalitis, raised ICP
- Cardiac/respiratory - MI, arrhythmia, heart failure, PE
- Surgery, anaesthesia, ICU, catheters, restraints, sleep deprivation
- Withdrawal - alcohol, benzodiazepines, nicotine, opioids
Deliriogenic drugs - the ones to hunt on the chart
- Anticholinergics (oxybutynin, amitriptyline, promethazine, hyoscine), benzodiazepines, opioids (especially pethidine and tramadol), corticosteroids, levodopa and dopamine agonists, antihistamines, antiepileptics, digoxin, lithium, fluoroquinolones, antipsychotics, any recent dose change or abrupt cessation
Mechanism
- Cholinergic deficiency + dopaminergic excess is the dominant model
- Neuroinflammation - peripheral inflammation -> cytokine passage across a permeable blood-brain barrier -> microglial activation
- Impaired oxidative metabolism, network disconnection, disrupted melatonin/circadian signalling
Diagnosis
Clinical. The diagnosis is made at the bedside with a collateral history and a test of attention.
A. Establish the baseline - the essential step
- Collateral history: what was this person like 2 weeks ago?
- Without it, delirium is called dementia and dementia is called delirium
B. Screening and assessment tools
- 4AT - the practical Australian ward tool: Alertness, AMT4, Attention (months backwards), Acute change/fluctuation
- >=4 = possible delirium +/- cognitive impairment; 1-3 = possible cognitive impairment
- CAM - (1) acute onset/fluctuation AND (2) inattention, PLUS either (3) disorganised thinking OR (4) altered conscious level
- CAM-ICU for the ventilated patient; RASS for arousal
- Bedside attention tests: months of the year backwards, serial sevens, digit span, days of the week backwards
C. Delirium vs dementia vs depression
| Delirium | Dementia | Depression | |
|---|---|---|---|
| Onset | Hours-days | Months-years | Weeks-months |
| Course | Fluctuating | Slowly progressive | Persistent, diurnal variation |
| Attention | Impaired - the key feature | Normal until late | Variable/distractible |
| Conscious level | Altered | Normal | Normal |
| Hallucinations | Common, visual | Late (except DLB) | Uncommon |
| Reversible | Usually | No | Yes |
- *Delirium superimposed on dementia is the commonest scenario - and is why every acute change in a person with dementia is delirium until proven otherwise*
- DLB fluctuates too - the discriminator is chronicity and the accompanying core features
D. Investigation - directed by the history and examination
- Bedside: vital signs, glucose, oxygen saturation, bladder scan for retention, ECG, medication chart review, pain and bowel assessment
- Bloods: FBE, UEC, calcium, magnesium, phosphate, LFT, CRP, TFT, B12, glucose, blood gas
- Urine: culture only if symptoms or signs of infection - *a positive dipstick in an older person usually means asymptomatic bacteriuria and does NOT explain delirium*
- CXR, blood cultures if febrile
- CT brain only if: focal neurological signs, head injury or fall, anticoagulation, reduced conscious level, no other cause found, or failure to improve
- EEG if non-convulsive status is possible; LP if meningitis/encephalitis suspected
- Consider thiamine deficiency and Wernicke encephalopathy in anyone malnourished or alcohol-dependent
Management
A. Prevention - the highest-yield intervention
- Multicomponent non-pharmacological programmes (HELP model) reduce incident delirium by ~30-40%
- Orientation - clock, calendar, familiar faces, repeated explanation
- Sleep hygiene - dark, quiet, no overnight observations where safe, no night-time sedatives
- Early mobilisation and avoidance of restraints
- Vision and hearing aids in place and working
- Hydration and nutrition; bowel and bladder care
- Avoid unnecessary catheters, lines and ward moves
- Medication review and deprescribing on admission
- *No drug prevents delirium* - prophylactic antipsychotics, melatonin and cholinesterase inhibitors have not shown benefit
B. Treat the cause
- Find and correct every precipitant; more than one is usually present
- Stop or reduce deliriogenic drugs; treat pain properly (untreated pain causes more delirium than opioids do)
- Relieve constipation and urinary retention; correct hypoxia, electrolytes and glucose
C. Supportive care - for every patient
- Calm, well-lit, quiet environment; consistent staff; family presence encouraged
- Reorientation, reassurance, explanation to patient and family that this is temporary and organic
- Mobilise, feed, hydrate, restore the sleep-wake cycle
- De-escalation before sedation; *avoid physical restraint* - it increases injury, agitation and duration
D. Medication - a last resort, not a treatment for delirium
- *Antipsychotics do NOT shorten duration or reduce severity of delirium* - they only blunt severe agitation
- Indication: severe distress, psychosis, or behaviour posing a risk of harm to self or others, when non-pharmacological measures have failed
- Haloperidol 0.25-0.5 mg oral/IM, or olanzapine 2.5 mg, or risperidone 0.25-0.5 mg; lowest dose, shortest duration, daily review and a documented stop date
- *Avoid all antipsychotics in DLB and Parkinson disease - use low-dose quetiapine if unavoidable*
- Monitor QT, extrapyramidal effects, falls, aspiration
- *Avoid benzodiazepines* - they worsen and prolong delirium
- Exceptions: alcohol or benzodiazepine withdrawal, and neuroleptic malignant syndrome
- Thiamine (parenteral, high dose) before glucose in anyone at risk of Wernicke encephalopathy
E. After the episode
- Document the delirium clearly in the discharge summary and inform the GP
- Cognitive reassessment 6-8 weeks after recovery - delirium unmasks or heralds dementia in a large proportion
- Explain to the patient and family - many are frightened and remember distressing hallucinations
- Falls, functional and medication review; consider geriatric follow-up
Associations
- Dementia - both the strongest risk factor and a frequent consequence
- Frailty, falls, fracture, functional decline
- Sensory impairment, malnutrition, pressure injury
- Polypharmacy and anticholinergic burden
- Alcohol and benzodiazepine dependence
- Post-operative cognitive dysfunction; ICU-acquired weakness and PTSD
- Elder abuse and unsafe discharge (identified during the admission)
Natural history & complications
- Often persists for weeks to months - "it resolves in a few days" is a myth; only ~20% have fully recovered by discharge
- Independently associated with:
- inc in-hospital mortality (~1.5-2x) and 12-month mortality
- inc length of stay, new institutionalisation, functional decline
- inc risk of subsequent dementia (~2-3x), and accelerated decline in existing dementia
- Hypoactive delirium has the worst outcomes - later recognition, more complications
- Persistent delirium at discharge predicts poor recovery - arrange follow-up cognitive assessment rather than labelling dementia in hospital
- Distressing memories of the episode are common and under-asked-about
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