Delirium

Delirium (“toxic confusional state”) is a relatively acute disorder in which impaired consciousness is associated with abnormalities of perception or mood.

Diagnosis (DSM-5)

A. Disturbance of consciousness, attention, and awareness. B. Onset over a short period. C. A change in cognition — perceptual disturbance, incoherent speech, disorientation, or memory impairment. D. A and C are not better explained by another disorder. E. There is evidence of a cause.

Approach by age

In a teenager, acute confusion/irrational behaviour is more likely drug toxicity/withdrawal, schizophrenia, severe depression, or a behavioural disorder.

In an elderly patient, ask: is this one of the 4 Ds” — dementia, delirium, depression, or drugs — or something else? If delirium, what’s the cause? Depression affects ~15% of over-65s and can mimic other causes of confusion. “Common culprit drugs: hypnotics, sedatives, oral hypoglycaemics, antihypertensives, digoxin, antihistamines, anticholinergics, and antipsychotics.

Causes, by category

Category	Examples
Prescribed drugs	Anticholinergics (antiparkinsonian agents, TCAs); tranquillisers/hypnotics (major and minor, plus lithium); antiepileptics; H1/H2 antihistamines; antihypertensives; corticosteroids; cardiac drugs (digoxin, diuretics, beta blockers); opioids; sympathomimetics
Withdrawal	Alcohol, opioids, amphetamines, cannabis, sedatives/anxiolytics
Infection	Specific — UTI, lower respiratory (pneumonia), otitis media, cellulitis. Intracranial — meningitis, encephalitis. Systemic — infective endocarditis, septicaemia, HIV, other viral infection, malaria
Metabolic	Uraemia, hepatic failure, electrolyte disturbance, dehydration
Endocrine	DKA, hypoglycaemia, hypo-/hyperthyroidism
Nutritional	Vitamin B-complex deficiency (especially B6/B12), Wernicke encephalopathy
Hypoxia	Respiratory failure, cardiac failure, anaemia
Vascular	Stroke, acute coronary syndrome
Intracranial	Head injury, seizures (including complex partial seizures)
Subtle” causes	Pain (e.g. herpes zoster), emotional upset, environmental change, the perioperative period, faecal impaction, urinary retention

Clinical approach

Build rapport, and get a collateral history — past medical and psychosocial history, including recent bereavement, family upset, or environmental change. Look for evidence of depression alongside organic causes.

Abbreviated mental status test: name of this place; city; year; month; date; year of birth; birthday; age; current and previous head of government. Interpretation: normal 9–10; mildly impaired 8–9; confused/demented ≤7.

Examination: focus on GCS and features of the underlying cause, with a rapid cardiovascular/respiratory/abdominal/neurological assessment.

Investigations (unknown cause): urinalysis/microscopy; blood and urine cultures; FBC/ESR; glucose; UEC; calcium/phosphate; vitamin D; TFTs; LFTs; B12/folate; ECG/troponin; CXR; non-contrast cerebral CT; syphilis serology; HIV; arterial blood gases.

Management

Principles: acute delirium is a medical emergency. Restore normal hydration/electrolytes/nutrition. If the cause is unknown, consider alcohol withdrawal and give empirical thiamine. Optimise the environment (calm atmosphere, a night light, orientation cues, familiar people present). Give oxygen if hypoxic.

Non-pharmacological: requires hospital-level observation with nursing supervision; calm, quiet surroundings; approach from the front, not the side; familiar people nearby; always introduce yourself and explain your purpose before approaching.

Pharmacological (adult doses — non-drug strategies come first; antipsychotics are not routinely recommended for delirium, and evidence does not support their routine use — reserve them for severe behavioural or psychological disturbance with an imminent risk of harm to the patient or others, once non-drug strategies have failed, and use the lowest effective dose for the shortest time; a single dose is usually enough):

• Psychotic behaviour, severe agitation, or risk of harm — haloperidol 0.5 mg orally as a single dose, OR olanzapine 2.5–10 mg orally in 1–2 doses, OR risperidone 0.5 mg orally as a single dose.
• If oral dosing isn’t possible — haloperidol 0.5 mg IM, or olanzapine 2.5 mg IM, each as a single dose (cover with benztropine 2 mg orally/IM for extrapyramidal effects).
• Anticholinergic delirium — tacrine hydrochloride 15–30 mg by slow IV injection, cautiously (an antidote).

See Acute Behavioural Disturbance for the general non-pharmacological approach, severity grading, and adult (non-frail) sedation regimens where delirium-specific dosing above doesn’t apply.

Monitor closely, and review clinically before giving further doses — avoid as needed” prescribing unless the indication and 24-hour maximum dose are clearly specified. “Avoid benzodiazepines when managing delirium generally — complications are common and long-acting benzodiazepines increase delirium — except for confirmed or suspected alcohol/sedative withdrawal, which needs its own management. Give oxygen for hypoxia; consider whether pain relief is needed; use lower parenteral doses in the very old/frail.