Delirium

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management

Definition

Delirium is an acute, fluctuating disturbance of consciousness, attention, and cognition, often triggered by an underlying medical condition or external factors.

Aetiology

1. Medical Causes:

  • Infections: urinary tract infections (UTIs), pneumonia, sepsis.
  • Metabolic disturbances: hypoglycaemia, hypercalcaemia, hyponatraemia.
  • Hypoxia: respiratory failure, anaemia.
  • Dehydration and malnutrition.

2. Neurological Causes:

  • Stroke or transient ischaemic attack (TIA).
  • Head trauma.
  • Epilepsy or postictal confusion.

3. Medication-Related Causes:

  • Psychoactive drugs: benzodiazepines, opioids, anticholinergics.
  • Polypharmacy: particularly in elderly patients.
  • Drug withdrawal: alcohol or sedatives.

4. Environmental Factors:

  • Hospitalisation (especially in intensive care units).
  • Sensory deprivation (e.g., visual or hearing impairment).
  • Sleep deprivation.

Pathophysiology

  • Disruption of neurotransmitter balance, particularly reduced acetylcholine and increased dopamine.
  • Inflammatory responses affecting brain function.
  • Hypoxia and metabolic disturbances impair neuronal signalling.

Risk factors

  • Older age (>65 years).
  • Dementia or cognitive impairment.
  • Multiple comorbidities.
  • Recent surgery or hospital admission.
  • Use of multiple medications (polypharmacy).
  • History of alcohol dependence.
  • Visual or hearing impairment.

Signs and symptoms

Core Features:

  • Acute onset: rapid development over hours to days.
  • Fluctuating course: symptoms vary throughout the day.
  • Inattention: easily distracted, unable to focus.
  • Disorganised thinking: incoherent speech, confused reasoning.

Other Features:

  • Altered consciousness: can range from drowsiness to hyperactivity.
  • Hallucinations: often visual (e.g., seeing people or animals).
  • Paranoia and agitation.
  • Reversed sleep wake cycle.

Investigations

  • Clinical assessment: diagnosis is based on history and examination.
  • Confusion Assessment Method (CAM): tool to identify delirium.
  • Blood tests:
    • Full blood count (rule out infection).
    • Urea and electrolytes (detect dehydration, renal impairment).
    • Liver function tests (rule out hepatic encephalopathy).
    • Glucose (hypo/hyperglycaemia).
    • Calcium (hypercalcaemia).
  • Urinalysis: check for urinary tract infection.
  • CXR: rule out pneumonia.
  • CT or MRI brain: if stroke or head injury suspected.

Management

1. Identify and Treat Underlying Cause:

  • Manage infections (e.g., antibiotics for UTI or pneumonia).
  • Correct metabolic imbalances (e.g., fluids for dehydration).
  • Review and stop medications that may contribute (e.g., sedatives, opioids).

2. Supportive Care:

  • Ensure a quiet, well lit, familiar environment.
  • Encourage family visits to provide reassurance.
  • Optimise hydration and nutrition.
  • Promote normal sleep patterns.

3. Pharmacological Management:

  • Only use medication if the patient is at risk of harming themselves or others.
  • Low-dose haloperidol (0.5–1 mg): used for severe agitation.
  • Avoid benzodiazepines unless treating alcohol withdrawal.
NeurologymypanotesDelirium