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First posted November 2009 by Charles Gomersall


  • Delirium: acute change in mental status or fluctuation in mood, associated with:
    • impaired attention
    • disorganized thinking
    • confusion
    • altered state of consciousness

Usually acute in onset and varies in intensity during day with peak at night. Usually reversible.

Easily detected in patient who is combative (active delirium) but may also be present in a calm and quiet patient (hypoactive delirium).


Delirium occurs in 15-40% of patients but is only detected in about 1/3 of these patients. Associated with higher mortality, prolonged length of ICU stay and increased healthcare costs

Risk factors

Pre-existing conditions

  • age>70 years
  • transfer from nursing home
  • visual or hearing impairment
  • depression, dementia, congestive heart failure, stroke or epilepsy
  • renal impairment
  • liver impairment
  • HIV infection
  • alcohol abuse in previous month
  • psychotropic drug use
  • malnutrition

Acute condition

  • severe illness
  • drug overdose or drug abuse
  • metabolic
    • hypo/hyperglycaemia
    • hypo/hypernatraemia
    • hypo/hyperthyroidism
  • body temperature disturbance
  • sepsis
  • hypoxaemia
  • dehydration
  • intracerebral lesion
  • brain trauma
  • fits


  • drugs:
    • anti-cholinergics
    • sedatives
    • analgesics
    • antibiotics, antihistamines, antihypertensives, bronchodilators, diuretics, H2 blockers, steroids
  • physical restraints
  • tube feeding
  • rectal or urinary catheter
  • central venous catheter


Diagnosis is often obvious in patients with active delirium but is harder to detect in patients with the more common hypoactive or mixed pictures. In these patients screening tools may be useful.

Step 1

Establish patient's pre-existing mental state - a large proportion of ICU patients have some form of cognitive impairment prior to admission. Subsequent tests for delirium must be interpreted in the light of this knowledge.

Step 2

Use screening tool to detect delirium


  • Confusion Assessment Method for the Intensive Care Unit
  • Most extensively validated score
  • Disadvantage:
    • requires patient to be able to evaluate and respond to a series of questions. Patients with impaired consciousness for other reasons may fail these tests and therefore be inappropriately classified as delirious
  • Patient classified as having delirium if has features 1 AND 2 AND either 3 OR 4


  • Intensive Care Delirium Screening Checklist
  • Less specific than CAM-ICU but this may be due, in part, to the inclusion of patients with neurological injury and structural neurological abnormalities in validation study of ICDSC but not CAM-ICU. Also, in part due to the inclusion of an assessment of sleep-wake cycle. Disturbance of sleep-wake cycle is common in ICU but is not necessarily associated with delirium
  • Level of consciousness is the first domain - if this impaired to the extent that vigorous stimulation is required to elicit a patient response (or worse) then the evaluation is terminated
  • Other domains are:
    • inattention
    • disorientation
    • hallucination
    • psychomotor agitation or retardation
    • inappropriate speech or mood
    • sleep/wake cycle disturbance
    • symptom fluctuation
  • screening is based on information collected from entire 8 h shift or from previous 24 h
  • Inclusion of a mandatory assessment of both consciousness and psychomotor retardation may make it a better tool than CAM-ICU to detect hypoactive delirium



  • Reassurance
  • Attention to patient comfort
  • Consider physical restraints
  • Correct potentially reversible risk factors


  • Usually a combination of sedation and neuroleptic eg haloperidol
  • Use of dexmedetomidine for sedation is associated with shorter duration of delirium compared to midazolam

Further reading

Chevrolet JC and Jolliet P. Clinical review: Agitation and delirium in the critically ill -significance and management. Crit Care, 2007;11:214

Devlin JW et al. Delirium assessment in the critically ill. Intensive Care Med, 2007; 33:929-40

Riker RR et al. Dexmedetomidine vs midazolam for sedation of critically ill patients. JAMA, 2009; 301(5):489-99

©Charles Gomersall, February, 2015 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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