Delirium is acute, fluctuating disturbance of attention and awareness with associated cognitive changes — a clinical syndrome, not a diagnosis. It always represents an underlying medical, medication, or substance-related cause. Recognition matters because the cause is often treatable; missing delirium and attributing symptoms to dementia leads to preventable harm.
Three cardinal features:
(1) Acute onset — develops over hours to days, not weeks to months. Family or staff can often pinpoint when the patient changed.
(2) Fluctuating course — symptoms wax and wane across the day. A patient may be lucid in the morning, confused by afternoon, lucid again briefly, then severely confused at night ("sundowning" is one pattern).
(3) Inattention — cannot sustain or shift attention. Cannot follow conversation, do simple cognitive tasks, or perform serial subtraction. This is the cognitive hallmark that distinguishes delirium from most dementias.
Subtypes:
Hyperactive — agitated, restless, sometimes combative, sometimes hallucinating. Easy to recognize because the behavior is dramatic. Common cause of "psychiatric consult" in hospital.
Hypoactive — withdrawn, lethargic, somnolent, decreased responsiveness. Often missed because the patient is "just sleeping" or "depressed." More common and more deadly than hyperactive.
Mixed — fluctuating between hyperactive and hypoactive features within hours.
Common causes (often multiple contributing):
Infection — UTI is the classic in older patients, pneumonia, sepsis, encephalitis.
Medications — anticholinergics (most common iatrogenic cause), benzodiazepines, opioids, corticosteroids, recent psychiatric medication changes.
Metabolic — electrolyte abnormalities (especially hyponatremia, hypercalcemia), glucose abnormalities, hepatic encephalopathy, uremia, thyroid disorders.
Substance — alcohol withdrawal (delirium tremens), drug intoxication, withdrawal from prescription medications.
CNS — stroke, subdural hematoma, seizure, hypertensive encephalopathy, structural lesion.
Surgical/perioperative — postoperative delirium, particularly after cardiac surgery and in elderly patients.
Workup: CBC, comprehensive metabolic panel, urinalysis with culture, chest X-ray if respiratory symptoms, medication review (always — many cases resolve with stopping a single anticholinergic), consider CT head if focal signs or fall, EEG if seizure suspected, additional workup based on context.
Management: identify and treat the cause. Address triggers: pain, infection, dehydration, constipation, urinary retention, sleep disruption, medication review. Non-pharmacologic: reorientation, family presence, glasses/hearing aids on, normal sleep-wake cycle support, daylight exposure, ambulation when possible. Antipsychotic only when severe and dangerous (haloperidol low dose, risperidone, quetiapine) — short course, document indication. Benzodiazepines worsen delirium except for alcohol/benzodiazepine withdrawal context.
Outcome: mortality is substantial — particularly hypoactive delirium. Patients who develop delirium during hospitalization have elevated risk of dementia, longer hospitalization, increased mortality, and difficulty returning to prior living situation. Recognition is the first step toward preventing these consequences.
When you encounter an acutely altered older patient, delirium is the diagnosis to consider first — not dementia worsening. Find the cause; treat the cause; the patient often returns to baseline.