Acute confusional state characterised by fluctuation in consciousness, cognition and attention

  • It is extremely common- complicating between 15 and 30% of hospital admissions.
  • Note that delirium is a syndrome, NOT a diagnosis.  The underlying cause may be trivial or may be life-threatening.
  • Confusion, itself, is not a cardinal feature BUT any patient presenting with confusion should be assumed to have a delirium (and a primary cause) until proven otherwise.
    • Delirium requires urgent treatment


  • Risk factors include age, cognitive impairment (e.g. dementia), frailty, visual impairment
  • Delirium due to a general medical condition:
    • infection (commonly UTI, pneumonia)
    • metabolic/electrolyte disturbance (hyponatraemia, hypernatraemia, hypoglycaemia, dehydration, renal failure, hyperthermia)
    • Cardiovascular and respiratory conditions (PE, MI, Heart failure)
      • Any cause of hypoxia
    • GI / GU conditions (constipation, diarrhoea, urinary retention, bladder catherisation, malnutrition)
    • Neuroendocrine conditions (thyroid dysfunction, subdural haematoma, encephalitis)
    • Severe pain
    • Loss of vision/hearing
    • It may be that the individual has multiple comorbidities too
    • Post-operatively is a common period to get delirium
  • Substance intoxication delirium
    • drugs e.g. BZDs, opioids, anti-parkinsonian drugs, TCAs, lithium, corticosteroids, digoxin, antipsychotics, beta blockers
      • NB Very common
  • Substance withdrawal delirium
  • Other causes e.g. relocation, sleep deprivations
  • Delirium with more than one cause


  • The key features are
    • Acute onset and fluctuating course
    • Change in cognition
      • The patient can be acutely confused, usually disorientated in person, time and place.  They may have memory impairment, language disturbance, poor attention span, they may be hallucinating/delusional
        • NB Hallucinations are often seen but are NOT crucial for the diagnosis
    • Altered conscious level (fluctuating conscious level)
      • Often with inattention and varying ability to follow commands
  • may have other symptoms e.g.
    • irregular sleeping pattern
    • memory deficits (mainly short term)
    • unsteady gait/tremor (wandering is not uncommon too)
    • changes in psychomotor behaviour
      • Hyperactive (agitated, emotional, oversensitive, noisy, aggressive, vigilant)
      • Hypoactive (lethargic, slow, immobile, sleepy/drowsy, quiet, reduced drinking/appetite, slurred speech)

Fluctuating symptoms are a key sign of delirium.  Stable and chronic symptoms are much more indicative of a dementia.


  • It is important to try and get a full collateral history from someone who knows the patient well (e.g. family, close friend, carer), including PMHx, RHx, Alcohol Hx/Social Hx, etc
  • Make sure to check vital signs

Confusion Assessment Method (CAM)

  • Part 1 (assessment of cognitive function)
    1. [Acute onset] Is there evidence of an acute change in mental state from the patient’s baseline?
    2. [Inattention]
      1. Did the patient have difficulty focusing attention (e.g. easily distracted/difficulty following conversation)?
      2. If present, did this behaviour fluctuate in presence/severity during the interview?
      3. Describe the behaviour
    3. [Disorganised thinking] Was the patient’s thinking disorganised or incoherent e.g. rambling/irrelevant conversation, unclear flow of though, flight of ideas etc?
    4. [Altered Level of Consciousness] Would you describe the patient’s level of consciousness as…
      1. Normal/Alert
      2. Vigilant (hyperalert, startled)
      3. Lethargic (drowsy, but arousable)
      4. Stupor (difficult to arouse)
      5. Coma (unarousable)
    5. [Disorientation] Was the patient disorientated at any time during the interview (time, place, person)?
    6. [Memory] Did the patient demonstrate any memory problems (either instructions or events)?
    7. [Perceptual disturbance] Did the patient have any evidence of perceptual disturbances (hallucinations, illusions, misinterpretation)?
    8. [Psychomotor disturbance] Did the patient have any unusually increased/decreased level of motor activity?
    9. [Altered sleep/wake cycle] Any excessive daytime sleepiness or insomnia?
  • Part 2 (distinguishes delirium/acute reversible confusion from dementia/long-term cognitive impairment)
    • For a diagnosis of delirium, the patient MUST display
      • Acute onset (1) and fluctuating course
      • inattention (2) OR cognitive impairment
      • Disorganised thinking (3) OR Altered level of consciousness (4)

More recently, the abbreviated 4-AT score is used in hospital setting:

  1. Alertness
    • Normal (alert, not agitated) or mildly sleepy after wakening <10s then normal (0)
    • Clearly abnormal (4)
  2. AMT 4
    • Age, DOB, Place, current year
      • No mistakes (0)
      • 1 mistake (1)
      • 2 or more mistakes (2)
  3. Attention
    • Months of the year backwards
      • 7 or more correct (0)
      • Starts but scores <7 or refuses to start (1)
      • Untestable (drowsy, inattentive) (2)
  4. Acute change/fluctuating course
    • Evidence of significant change or fluctuation in: alertness, cognition, other mental function (e.g. paranoia/hallucinations) arising over the last 2 weeks and still evident in last 24 hours
      • No (0)
      • Yes (4)
  • 4 or above- possible delirium +/- cognitive impairment
  • 1-3- possible cognitive impairment
  • 0- both unlikely (although still possible if patient untestable)

Mini-Mental State Examination (note that this assessment is actually copyrighted)


These will ultimately depend on the suspected underlying cause is.  However, in general:

  • Blood tests (particularly FBC, U&Es, glucose)
    • if there is a temperature, blood cultures
    • TFTs may also be useful
    • CRP
  • Urinalysis; MSU
  • ABGs
  • CT head (to rule out a more sinister cause e.g. subdural haematoma)
    • CXR may also be a good idea if there are any chest signs/symptoms or hypoxia


First, identify and reverse any underlying causes.  Medical treatment includes

  • Oxygen (help oxygenation to the brain)
  • If infection, appropriate antibiotics; if hypothyroid, levothyroxine etc etc
    • NB treatment of the underlying condition should be approached with caution e.g. be wary of using high dose diuretics for heart failure/pulmonary oedema as it may precipitate delirium due to hyponatraemia/hypokalaemia.

Non-pharmacological management is crucial:

  • Continuity of staff; quiet and calm environment; low night lighting; clearly visible clock/calendar; familiar people; bed low as possible; normal sleep patterns
  • Avoid restraint, arguments, catheterising/venous access (can worsen due to infection risk and patients will often pull them out), too much movement/overstimulation

Pharmacological management (NB this should really only be considered if the patient is excessively agitated, becoming a danger to them self or others etc.  Do NOT routinely use antipsychotic medications for patients with delirium)

  • Haloperidol is 1st line
    • Oral if possible, low dose initially (0.25-0.5mg- max 5mg in 24hrs)
    • If PO not possible, IM inj (1-2mg)
    • Avoid long term use
  • Respiridone could be an alternative but generally increasing the dose of haloperidol slowly should work
  • Lorazepam should ONLY be used in Lewy body/PD dementia or alcohol withdrawal
    • Can make delirium worse

Differential Diagnoses

  • If confusion persists despite treating reversible causes of delirium, other causes of confusion can be sought e.g.
    • Delirium Tremens (Alcohol withdrawal)
    • Dementia
    • Psychiatric diagnoses (Schizophrenia, mood disorder with psychosis…)
    • Brain pathology (e.g. tumours)

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