Critical Care Trauma Centre

Significance of Delirium

Delirium is a syndrome (not a disease) that causes acute cerebral dysfunction. Cognitive or perceptual distrubances develop acutely over a short period of time in conjunction with a general medical condition, substance use or abuse or drug withdrawal (including prescription or illegal drug use or toxins).

Hallmarks of Delirium

  • Decreased attention span
  • Waxing and waning confusion
  • Acute onset in the setting of another illness



The DSM IV is the fourth version of the Diagnositic and Statistical Manual of Mental Disorders. The DSM IV defines the required criteria that a patient must meet to be diagnosed with a mental disorder.  All recognized mental disorders are listed. The "Gold Standard" for the diagnosis of delirium is the criteria listed in the DSM IV for Delrium.

DSM IV : Delirium

  • Disturbance of consciousness with reduced ability to focus, sustain, or shift attention
  • A change in cognition or the development of a perceptual disturbance that is not better accounted for by a preexisting, established, or evolving dementia
  • The disturbance develops over a short period of time (usually hours to days) and tends to fluctuate during the course of the day
  • There is evidence from the history, physical examination, or laboratory findings that the disturbance is caused by a medical condition, substance intoxication, or medication side effect1

Dementia, depression and mental disorders can produce signs and symptoms that make the diagnosis of delirium more challenging. As well, patients can develop delirium on top of a baseline of dementia or a mental disorder.

Why is delirium important?

  • Delirium is common (reported rates range between 10-80%)14.  Two Canadian ICU trial and a Multicentre Point Prevalence study (11 centre from North and South America and Spain) reported rates of ICU delirium of 31.8-35%. Because delirium can only be identified in patients who are awake enough for screening, this likely under-reports the true incidence7,8,10
  • In a Canadian trial, 33% of non-comatose patients had sub-syndromal delirium (some but not all delirium criteria present)7,8
  • Delrium and subsyndromal delirium are both associated with increased mortality6,7,8,9
  • Increases adverse events (e.g., falls, tube removal)
  • Increases restraint use (chemical and mechanical), which can increase the risk for delirium and intensify patient agitation, paranoia and distress
  • Increases medical complications (e.g., aspiration, wound trauma)
  • Distressing to family members
  • Increases healthcare costs
  • Many patients never return to prior cognitive function
  • Even young patients can have prolonged cognitive disturbances that can persist for months after delirium
  • Some patients will experience Post Traumatic Stress Disorder

Types of Delirium

In one tertiary study of 614 MICU patients, delirium was detected in 71.8% of patients > 65 and 57.4% of those < 65. Of these, 3 motor subgroups were identified as follows9:

Hyperactive delirium:

  • Delirious patients who are agitated and hyperactive around the clock represent a small portion of delirious patients (~1.6% of patients diagnosed with delirium)

Hypoactive delirium:

  • Patients who were flat with persistently decreased psychomotor activity represented ~43.5% of delirious patients
  • Elderly patients are more likely to develop hypoactive delirium

Mixed delirium:

  • Patients with fluctuating psychomotor activity (demonstrating pattern of both hyper and hypoactive delirium) represented 54.9% of delirious patients

Important Facts?

  • There are many medical problems, drugs, treatments and situations that increase the risk for delirium (risk assessment and prevention will be discussed in Module II)
    • Use of benzodiazepines may be one of the most important risk factors
  • We believe we may be able to reduce the incidence of delirium by targeting risk factors, however, this belief is primarily intuitive
  • The treatment priority for delirium is to treat precipitating illnesses and identify other associated risk factors
  • "Ugly" reasons for behaviour changes must always be ruled out first (e.g., changes in ABCs, or glucose or a new neurological event)
  • We can often modify delirious behaviour with medications, however, we don't know whether treatment actually improves outcomes
    • In at least one study of elderly patients with delirium, pneumonia rates increased with the use of antipsychotic medications5
  • We do not know the best treatment

But: We need to begin by understanding our incidence of delirium with routine screening!




  1. American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th ed., text rev.). Washington, DC: Author.
  2. Bergeron, N., Dubois, M., Dumont, M., Dial, S., and Skrobik, Y. (2001). Intensive care delirium screening checklist: evaluation of a new screening tool. Intensive Care Medicine. 27:859-864.
  3. Ely, W. CAM - ICU. Copyright © 2002, E. Wesley Ely, MD, MPH and Vanderbilt University, all rights reserved
  4. Girard, T., Pandharipande, P., and Ely, W., (2008). Delirium in the intensive care unit. Critical Care. Available online
  5. Knol, W., van Marum, R., Jansen, P., Souverein, P., Schobben, A., and Egerts, A. (2008). Antipsychotic Drug Use and Risk of Pneumonia in Elderly People. J Am Geriatr Soc 56:661–666.
  6. Lin, S., Liu, C., Wang, C., et al. (2004). The impact of delirium on the survival of mechanically ventilated patients. Crit Care Med; 32:2254 –2259
  7. Ouimet, S., Riker, R., Bergeron, N., Cossette, M., Kavanagh, B., and Skrobik, Y. (2007). Subsyndromal delirium in the ICU: evidene for a disease spectrum. Intensive Care Med. Jun;33(6):1007-13. Epub 2007 Apr 3.
  8. Oumet, S., Kavanagh, B., Gottfried, S., and Skrobik, Y. (2007). Incidence, risk factors and consequences of ICU delirium. Intensive Care Med.Jan;33(1):66-73. Epub 2006 Nov 11.
  9. Peterson, J., et al. (2006). Delirium and its motoric subtypes; a study of 614 critically ill patients. Journal of Geriatrics. 54:479-484.
  10. Salluh et al. (2010). Delirium epidemiology in critical care (DECCA): an international study. Critical Care 2010, 14:R210.