ICU Delirium

Original Editor - Karen Wilson Top Contributors - Karen Wilson, Kim Jackson and Adam Vallely Farrell


Source: Wikimedia Commons, Author: Calleamanecer, License: Creative Commons Attribution-Share Alike 3.0 Unported
As the survival of critically ill patients improves, ICU delirium has become a growing public health issue. Delirium is defined as a rapid change in consciousness (hours to days) characterized by reduced environmental awareness, decreased attention and altered cognition. These clinical features can manifest themselves as memory deficits, disorientation, hallucinations, fluctuating levels of alertness, and motor abnormalities.[1]

There is a significant burden that is associated with this condition. Compared with people who do not develop delirium, people who develop ICU delirium may:

  • need to stay longer in hospital or in critical care
  • have an increased incidence of dementia
  • have more hospital-acquired complications, such as falls and pressure sores
  • be more likely to need to be admitted to long-term care if they are in hospital
  • be more likely to die[2]

According to Ely et al[3] as much as 83% of ICU patients on mechanical ventilation develop delirium. This figure is significant as ICU delirium is associated with negative patient and healthcare outcomes. These outcomes include increased time on mechanical ventilation,[4] longer ICU and hospital length of stay, [5][6] elevated health care costs,[7] increased cognitive dysfunction[4] and increased risk of death.[8]

Delirium Subtypes

Delirium can be divided into 3 subtypes: hyperactive, hypoactive, and mixed. The table below matches each subtype with common clinical manifestations.

Subtype Clinical Manifestations
Hyperactive Agitation, restlessness, emotional lability, hallucinations
Hypoactive Lethargy, decreased responsiveness, slowed motor skills
Mixed Fluctuation between hyper- and hypo- active symptoms

[Source: Meagher D. Motor subtypes of delirium: past, present and future. Int Rev Psychiatry. 2009 Feb;21(1):59-73]

In critically ill patients, mixed delirium is the most common subtype (54.9%). Hypoactive delirium is second (43.5%), followed by a small percentage of patients who display purely hyperactive symptoms (1.6%) .[9] ICU patients aged 65 and older are particularly susceptible to hypoactive delirium.[9]

Causes and Risk Factors

Delirium develops as a result of multiple causes and risk factors. Old age, dementia, depression, smoking, and alcohol use are among the personal factors that increase patient susceptibility.[10][11] In addition, another 20+ risk factors related to medical status have been identified by the literature.[12] Below is a common mnemonic used to help clinicians identify causes related to illness and treatment:

Illness and Treatment-Related Causes of Delirium
D Drugs
E Eyes, ears, and other sensory deficits
L Low O2 states (e.g. heart attack, stroke, and pulmonary embolism)
I Infection
R Retention (of urine or stool)
I Ictal state
U Underhydraton/undernutrition
M Metabolic causes (DM, Post-operative state, sodium abnormalities)

[Adapted from: Saint Louis University Geriatrics Evaluation Mnemonics Screening Tools (SLU GEMS). Developed or compiled by: Faculty from Saint Louis University Geriatrics Division and St. Louis Veterans Affairs GRECC.]

Other risk factors common to the hospital setting include the absence of daylight, lack of visitors, sleep deprivation, immobility, and hospital lines.[10]


The pathophysiology of delirium is not well understood. Theories related to its development and progression cite anatomical changes in the brain and neurotransmitter imbalances (ex. abnormal levels of serotonin, decreased acetylcholine, excess dopamine) as possible physiologic mechanisms.[13]


Given the unknown pathophysiology, there is no imaging or laboratory tests that can diagnose delirium. As a result, delirium is a diagnosis of exclusion that requires careful clinical testing and observation.

Assessment and Monitoring

Guidelines for treating Pain, Agitation, and Delirium (PAD)[14] recommend two tests for the assessment of delirium in adult ICU patients:

  1. The Intensive Care Delirium Screening Checklist (ICDSC)
  2. The Confusion Assessment Method for the ICU (CAM-ICU)

The following video demonstrates how to perform the CAM-ICU.

Prevention and Treatment

In 2010, Vasilevskis et al.[15] proposed the ABCDE model to screen and prevent delirium among ICU patients. The updated version is expanded to include family engagement.[16] The concepts corresponding to each letter of the mnemonic are as follows:

Evidenced-Based Prevention and Treatment Strategies for ICU Delirium
A Assess, prevent and manage pain
B Both Spontaneous Awakening Trials (SAT) and Spontaneous Breathing Trials (SBT)
C Choice of analgesia and sedation
D Delirium: assess, prevent and manage
E Early mobility and exercise
F Family engagement and empowerment

In addition to ABCDEF bundle, Brummel et al.[10] advocate identifying and correcting for individualized causal factors of delirium (ex. minimizing unnecessary noise during rest hours to reduce sleep deprivation).

Implications for Physical Therapy Practice

Physical therapists have an important role in preventing and managing ICU delirium. Perhaps the most important measure is engaging patients in early mobilization in conjunction with nurses, occupational therapists, and physicians. Early mobilization in the ICU has been shown to reduce the number of days on mechanical ventilation,[17][18] decrease ICU and hospital length of stay[19] and is the only intervention to date proven to decrease the number of days of delirium[18]. Frequent patient orientation, use of a patient's customary vision and hearing aids, and family training and education are additional interventions that can be integrated into therapy sessions.[13] The CAM-ICU is a quick and easy tool for physical therapists to assess and monitor the course of a patient's delirium over time.

Differential Diagnosis

The multifactorial nature of delirium can make it easy to mistake for other brain dysfunctions. Below is a non-exhaustive list of conditions that should be considered in the differential diagnosis of ICU delirium:

  • Dementia
  • Psychiatric Disorders (ex. schizophrenia)
  • Depression
  • Traumatic Head Injury
  • Pain
  • Stroke
  • Myocardial Infarction

[Sources: American Family Physician- Delirium, BMJ Best Practice- Assessment of Delirium]

Clinical Guidelines

NICE Guidelines on Delirium have been updated in March 2019. They recommend an initial risk factor assessment on admission. The interventions recommended to prevent delirium include; ensuring people who are at risk are not moved within and between wards or rooms unless absolutely necessary, provision of a multicomponent intervention tailored to the person's individual needs and care settings. Initial management should include identifying and managing the underlying cause or combination of causes. Ensure effective communication and reorientation and provide reassurance for people diagnosed with delirium. [20]

If a person with delirium is distressed or considered a risk to themselves or others and verbal and non-verbal de-escalation techniques are ineffective or not appropriate, consider giving short-term haloperidol starting at the lowest clinically appropriate dose. [20]

A systematic review and meta-analysis in 2015 reported that almost a third of patients who are admitted to an intensive care unit develop delirium, and these patients are at increased risk of dying during admission, longer stays in hospital, and cognitive impairment after discharge.[21]

Further Reading

For further reading, the ICU Delirium and Cognitive Impairment Study Group is a great resource for learning and staying up to date on best practices for the prevention and management of ICU delirium.

For up to date research and developments in the assessment. prevention and management of delirium in ICU :


  1. American Psychiatric A. Diagnostic and statistical manual of mental disorders. 5th edition. Washington, DC: American Psychiatric Association; 2013
  2. Young J, Murthy L, Westby M, Akunne A, O’Mahony R. Diagnosis, prevention, and management of delirium: summary of NICE guidance. Bmj. 2010 Jul 28;341:c3704.
  3. Ely EW1, Inouye SK, Bernard GR, Gordon S, Francis J, May L, Truman B, Speroff T, Gautam S, Margolin R, Hart RP, Dittus R. Delirium in mechanically ventilated patients: validity and reliability of the confusion assessment method for the intensive care unit (CAM-ICU). JAMA 2001; 286(21): 2703-10
  4. 4.0 4.1 Salluh J, Wang H, Schneider EB, Nagaraja N, Yenokyan G, Damluji A, Serafim RB, Stevens RD. Outcome of delirium in critically ill patients: systematic review and meta-analysis. BMJ 2015; 350: h2538
  5. Ely EW, Gautam S, Margolin R, Francis J, May L, Speroff T, Truman B, Dittus R, Bernard R, Inouye SK. The impact of delirium in the Intensive care unit on hospital length of stay. Intensive Care Med 2001; 27:1892-1900
  6. Thomason JW, Shintani A, Peterson JF, Pun BT, Jackson JC, Ely EW. Intensive care unit delirium is an independent predictor of longer hospital stay: a prospective analysis of 261 non-ventilated patients. Crit Care 2005; 9(4): R375–R381
  7. Milbrandt, E.B., Deppen, S., Harrison, P.L., Shintani, A.K., Speroff, T., Stiles, R.A., Truman, B., Bernard, G.R., Dittus, R.S., Ely, E.W. Costs Associated with Delirium in Mechanically Ventilated Patients. Crit. Care Med. 32 (4):955-962, 2004
  8. Ely EW, Shintani A., Truman B, Speroff T, Gordon SM, Harrell FE, Inouye SK, Bernard GR, Dittus RS. Delirium as a predictor of mortality in mechanically ventilated patients in the intensive care unit. JAMA 2004; 291(14): 1753-62
  9. 9.0 9.1 Peterson J, Pun BT, Dittus RS, Thomason JW, Jackson JC, Shintani AK, Ely EW. Delirium and its motoric subtypes: a study of 614 critically ill patients. J Am Geriatr Soc. 2006; 54(3):479-84
  10. 10.0 10.1 10.2 Brummel N, Girard T. Preventing delirium in the intensive care unit. Crit Care Clin 2013; 29(1): 51–65
  11. McNicoll L, Pisani MA, Zhang Y, Ely EW, Siegel MD, Inouye SK. Delirium in the intensive care unit: occurrence and clinical course in older patients. J Am Geriatr Soc 2003; 51:591-598
  12. Cavallazzi R, Saad M, Marik PE. Delirium in the ICU: an overview. Ann Intensive Care 2012; 2: 49
  13. 13.0 13.1 ICU Delirium and Cognitive Impairment Study Group. For Medical Professionals-- ABCDEF's of prevention and safety. Accessed March 8, 2018.
  14. Barr J, Fraser GL, Puntillo K, Ely EW, Gélinas C, Dasta JF, Davidson JE, Devlin JW, Kress JP, Joffe AM, Coursin DB, Herr DL, Tung A, Robinson BR, Fontaine DK, Ramsay MA, Riker RR, Sessler CN, Pun B, Skrobik Y, Jaeschke R; American College of Critical Care Medicine. Clinical practice guidelines for the management of pain, agitation, and delirium in adult patients in the intensive care unit. Crit Care Med. 2013; 41(1):263-306
  15. Vasilevskis EE1, Pandharipande PP, Girard TD, Ely EW. A screening, prevention, and restoration model for saving the injured brain in intensive care unit survivors. Crit Care Med 2010;38(10 Suppl):S683-91.
  16. ICU liberation. ABCDEF Bundle. Accessed March 11, 2018.
  17. Schweickert WD, Pohlman MC, Pohlman AS, Nigos C, Pawlik AJ, Esbrook CL, Spears L, Miller M, Franczyk M, Deprizio D, Schmidt GA, Bowman A, Barr R, McCallister KE, Hall JB, Kress JP. Early physical and occupational therapy in mechanically ventilated, critically ill patients: a randomised controlled trial. Lancet 2009; 373(9678):1874-82
  18. 18.0 18.1 Needham DM, Chandolu S, Zanni J. Interruption of sedation for early rehabilitation improves outcomes in ventilated, critically ill adults. Aust J Physiother 2009; 55(3):210
  19. Morris PE, Goad A, Thompson C, Taylor K, Harry B, Passmore L, Ross A, Anderson L, Baker S, Sanchez M, Penley L, Howard A, Dixon L, Leach S, Small R, Hite RD, Haponik E. Early intensive care unit mobility therapy in the treatment of acute respiratory failure. Crit Care Med 2008;36(8):2238-43
  20. 20.0 20.1 National Institute for Health and Care Excellence. (2013). Delirium: prevention, diagnosis and management. Retrieved from
  21. Salluh JI, Wang H, Schneider EB, Nagaraja N, Yenokyan G, Damluji A, Serafim RB, Stevens RD. Outcome of delirium in critically ill patients: systematic review and meta-analysis. bmj. 2015 Jun 3;350:h2538.