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Delirium

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Overview

Also known as an acute confusional state, delirium describes acute, fluctuating consciousness, cognition, and perception that develops over hours to days. Behavioural disturbances, personality changes, and psychotic features may also be seen. 

Delirium is generally caused by the interaction between a vulnerable patient and a precipitating stimulus.

Delirium is very common, especially in older people, and many people do not return to their baseline levels of function after recovering. Delirium can be prevented and treated if diagnosed and managed early.

Subtypes of delirium

  • Hyperactive delirium:
    • May be restless and agitated
    • May be aggressive and hyper-alert
  • Hypoactive delirium:
    • May be drowsy and withdrawn
    • May show somnolence
    • Most under-recognised and carries the highest risk of mortality
  • Mixed delirium:
    • Features of both hyper- and hypoactive delirium
    • Patients can cycle between the two

Delirium is associated with multiple adverse outcomes:

  • Increased length of stay in hospital
  • Increased falls risk
  • Increased risk of institutionalisation after discharge
  • Increased risk of functional decline
  • Increased mortality

Epidemiology

  • Prevalence is higher with increasing age
  • Delirium is thought to affect up to 50% of people >65 years old in hospital
  • It may occur in up to 87% of people in intensive care admissions

Risk Factors

  • Older age (generally >65 years old)
  • Cognitive impairment e.g. dementia
  • Frailty
  • Multimorbidity
  • Significant injuries (e.g. hip fractures)
  • Functional impairment (e.g. immobility)
  • Visual or hearing impairment
  • History of delirium
  • History of alcohol excess
  • Dehydration
  • Poor nutrition
  • Polypharmacy
  • Coexisting medical illness
  • Terminal phase of illnesses
  • Surgery

Precipitating Factors

The mnemonic PINCHMME can be used to remember factors that may precipitate delirium:

  • Pain
  • Infection
  • Nutrition:
    • Have they been eating?
  • Constipation and urinary incontinence:
    • How are their bowels and bladder?
  • Hydration:
    • Dehydration
  • Medications
    • Sedatives, anticholinergics, alcohol, tricyclic antidepressant overdoses, anti-Parkinsonism medications, corticosteroids
  • Metabolic
  • Environment
    • Changes in the environment can commonly precipitate delirium

Other factors are sleep deprivation or any significant cardiorespiratory, neurological, or endocrine problem.

Presentation

Do not assume any confusion is due to long-term dementia or pre-existing cognitive decline. Suspect delirium in all people with a sudden change in behaviour that may be reported by the patient, a carer, or a relative.

If possible, check the previous level of function of the patient through previous admission notes or collateral history taking.

Symptoms usually have an acute/subacute onset and a fluctuating course. There may be:

  • Altered cognition:
    • Disorientation, memory problems, confusion, poor concentration
    • Short-term memory loss is generally affected more than long-term memory loss
  • Disorganised thinking:
    • Rambling, irrelevant conversation, unclear flow of ideas, difficulty expressing concerns
  • Altered perception:
    • Paranoid delusions, misperceptions, visual/auditory hallucinations
  • Emotional changes:
    • Intermittent or labile changes in mood/emotions
  • Altered level of consciousness:
    • Reduced awareness of surroundings, sleep cycle problems (e.g. daytime drowsiness, night-time insomnia)
  • Features of a delirium subtype:
    • Hypoactive (more common):
      • Lethargy, reduced mobility, lack of interest in activities, reduced appetite, quiet and withdrawn
    • Hyperactive:
      • Agitation, restlessness, sleep disturbance, hypervigilance, wandering
    • Mixed:
      • A combination of hypo- and hyperactive symptoms may be present
  • Falling and appetite loss are warning signs of delirium

Assessment

Overview

A thorough history should be taken. Notes on this can be found here.

A physical examination should be performed to identify signs of an underlying cause:

  • Vital signs including temperature, blood pressure, heart rate, capillary refill time, and pulse oximetry:
    • May identify fever, hypoxia, or hypotension
  • Blood glucose:
    • May identify hypoglycaemia
  • Cardiovascular examination:
  • Respiratory examination:
  • Abdominal examination:
    • May identify acute abdomen, constipation, faecal impaction (a digital rectal examination may be necessary if it is suspected), urinary retention, and urinary tract infection (UTI)
  • Neurological examination:
  • Musculoskeletal examination:
  • Skin examination:
    • May identify infection, pressure sores, or ulcers
  • Other features:
    • Pain, dehydration, cachexia
    • Causes of sensory impairment (e.g. impacted earwax, ill-fitting/non-functioning hearing aids, and glasses)

Differential Diagnoses

Dementia

  • Impaired consciousness suggests delirium (except if Lewy body dementia)
  • Fluctuating symptoms suggest delirium
  • Hallucinations suggest delirium
  • Agitation suggests delirium
  • Delusions suggest delirium

Depression

  • Persistent low mood
  • Anhedonia
  • Lack of enjoyment
  • Low self-esteem
  • Suicidal ideation

Manic phase of bipolar disorder

  • History of normal mood interspersed with depression and mania/hypomania
  • Mood elevation
  • Grandiosity

Investigations and Diagnosis

Cognitive assessment

Delirium can be diagnosed using:

  • The CAM criteria for delirium
  • The DSM-V criteria for delirium
  • The 4A’s test (4AT)

If there is diagnostic doubt, seek help from a specialist.

All patients should have full and thorough physical examinations, including the airways, breathing, circulation, and vital signs.

Investigations

Most patients require admission for same-day investigations and treatment. Investigations include:

  • Vital signs such as O2, pulse etc. if not already done in physical exam:
    • May identify fever, hypoxia, or hypotension
  • Blood glucose:
    • May identify hypoglycaemia
  • Full blood count (FBC):
  • Urea and electrolytes (U&Es):
    • May identify renal failure and/or electrolyte disturbances
  • Urine dipstick and urinalysis:
    • May identify a UTI
  • Chest X-ray:
    • May identify causes of hypoxia e.g. pneumonia
  • Drug levels if patients take drugs that may contribute in toxic levels:
    • E.g. Digoxin, lithium, and alcohol
  • ECG and troponins:
    • To screen for myocardial infarction and arrhythmias
  • Liver function tests (LFTs):
    • To screen for liver pathology
  • Blood and urine cultures:
    • If infection suspected
  • Lumbar puncture:
  • X-rays of bones:
    • If fractures are suspected

Other investigations include:

  • Neuroimaging:
    • CT/MRI brain
  • Holter monitor:
    • For arrhythmias
  • NT-proBNP:
    • For heart failure
  • Echocardiography:
    • For heart failure
  • CTPA or V/Q scan:
    • For pulmonary embolism
  • Abdominal x-ray:
    • For bowel ischaemia
  • Abdominal ultrasound:
  • Electroencephalogram (EEG):
  • Trial IV thiamine:

Some investigations may need to be carried out more urgently in specific scenarios e.g. CT head for a stroke.

Management

All patients

  • 1st-line: identify and manage the underlying cause.
  • If distressed/risk to themselves or others and verbal de-escalation techniques fail to work, short-term haloperidol is given.
    • Due to extrapyramidal side effects, this must be avoided or used with caution if the patient has Parkinson’s disease or dementia with Lewy bodies.

Monitoring

  • During a hospital stay, patients should be observed daily for any changes in cognition
  • If delirium does not resolve, patients should be re-evaluated for underlying causes.
  • Patients should be followed up and assessed for possible dementia.

Patient Advice

  • Patients should be educated that delirium is common and often temporary.
  • People at risk and families/carers should be safety-netted on sudden changes or fluctuations in behaviour.

Complications

  • Hospital-acquired infections e.g. Clostridium difficile and MRSA
  • Falls and subsequent fractures e.g. femoral or hip fractures
  • Pressure sores
  • Residual cognitive impairment
  • Some patients progress to stupor, coma, and eventually death.

Prognosis

  • Some patients do not recover and continue to have delirium
  • Some patients may need to be institutionalised after delirium
  • Short-term delirium has no effect on mortality, but longer-term delirium has an increased risk of mortality 
  • Patients with malignancy or HIV have a worse prognosis

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