Red flags
- Agitated delirium with hyperthermia and autonomic instability - sympathomimetic/serotonergic/anticholinergic toxicity
- Delirium tremens (48-96h post last drink) - untreated mortality 1-5%
- Hypoactive delirium mistaken for depression/fatigue - opioid, benzodiazepine, or anticholinergic accumulation
- Rigidity + fever + delirium - NMS
Differential by mechanism
Toxidrome-based causes
- Anticholinergic: agitated delirium, mydriasis, dry hot skin, urinary retention, tachycardia - "mad as a hatter, red as a beet, dry as a bone"
- Sympathomimetic: agitation, mydriasis, tachycardia, hyperthermia (stimulants, cocaine)
- Sedative-hypnotic withdrawal: alcohol, benzodiazepine - agitated, tremor, autonomic hyperactivity, hallucinations
- Opioid/sedative intoxication or accumulation: hypoactive, miotic (opioid) or normal pupils, respiratory depression
Drug accumulation in the elderly
- Anticholinergic burden (multiple mildly anticholinergic drugs), opioid accumulation in renal impairment, benzodiazepine accumulation
Other
- Serotonin syndrome, NMS, corticosteroid-induced delirium/psychosis
Focused history
- New drug, dose increase, or renal/hepatic impairment altering clearance
- Alcohol/benzodiazepine use and timing of last dose
- Baseline cognition (acute change is the key discriminator from dementia)
- Full medication reconciliation for cumulative anticholinergic/sedative burden
Focused examination
- CAM (Confusion Assessment Method) - acute onset, fluctuation, inattention +/- disorganised thinking or altered consciousness
- Pupils, skin (dry vs diaphoretic), temperature, tone, reflexes
- Bowel sounds, urinary retention (anticholinergic)
Investigation strategy
- Exclude organic causes first - glucose, UEC, calcium, infection screen, oxygenation
- Drug levels where relevant (digoxin, lithium)
- ECG if QT/QRS-affecting drugs on board
Management
1. Treat the reversible cause
- Stop/reduce causative drug(s); correct metabolic derangement; treat withdrawal per specific protocol (alcohol/benzodiazepine)
2. Agitated delirium
- Verbal de-escalation and environmental measures first
- Benzodiazepines for sedative/alcohol withdrawal delirium specifically
- Avoid benzodiazepines in most other causes of delirium (worsens confusion) - use low-dose antipsychotic (haloperidol, olanzapine) if pharmacological sedation needed and not anticholinergic/serotonergic in origin
- Physical restraint only as last resort, minimise duration
3. Hypoactive delirium
- Easily missed - screen for it, treat the underlying cause, avoid further sedating drugs
- Optimise sleep-wake cycle, mobilise early, correct sensory deficits (glasses, hearing aids)
4. Specific reversal
- Physostigmine for severe anticholinergic delirium (specialist use, risk of cholinergic crisis/seizure - reserve for refractory cases)
Traps
- Benzodiazepines worsen most delirium except alcohol/sedative withdrawal - a common prescribing error
- Hypoactive delirium is under-recognised and often mislabelled as depression or "just tired"
- Anticholinergic delirium can be worsened by antipsychotics with their own anticholinergic activity (e.g., olanzapine) - choose a lower-anticholinergic agent if antipsychotic needed
- Physical restraint increases agitation and injury risk - use only when de-escalation and pharmacological measures have failed
Talk track
1. Match the sedative to the cause
- "Benzodiazepines are for withdrawal delirium specifically - elsewhere they usually make confusion worse."
2. Look actively for hypoactive delirium
- "The quiet, withdrawn patient gets the same CAM screen as the agitated one."
8 of 8 sections written · drafted 2026-09-13