Skip to main content

Delirium assessment in the intensive care unit: patient population matters


The high prevalence and pervasive impact of delirium in critically ill patients has been demonstrated in multiple studies. Subsequently there has grown a body of literature regarding delirium assessment in critical illness. The present commentary briefly discusses delirium screening in an intensive care unit environment.

The Diagnostic and Statistical Manual of Mental Disorders IV diagnostic criteria for delirium are disturbances of consciousness and change in cognition that develops over a short period of time and fluctuates during the course of the day. There also must be evidence from the history, physical examination, or laboratory findings that this disturbance is caused by the direct physiological consequences of a general medical condition.

The prevalence of delirium in critical illness and the importance of its impact on intensive care unit (ICU) outcomes have recently gained recognition in the literature [1]. Delirium may persist after an ICU stay and may have long-term effects on cognitive and functional abilities as well as impacting on the patient's quality of life. Current critical care practice guidelines recommend routine delirium screening [2].

While there has been ongoing research into delirium in noncritically ill patients for many years, only recently has attention been given to delirium in the ICU [3]. The instruments used to assess delirium in noncritically ill patients are often not suited to the unique needs of a critical care population. The characteristics of patients in a critical care environment have hindered development of standardized delirium assessments. Some issues that ICU delirium screening instruments need to address are the inability of intubated patients to participate in a verbal assessment, the severity of illness, and limitations on staff time that may preclude a lengthy cognitive assessment.

There are six delirium assessment instruments in the literature that have been evaluated in an ICU setting. These instruments are presented in Table 1 and are based in part on the Diagnostic and Statistical Manual of Mental Disorders criteria for diagnosing delirium. Each of these scales has been validated, but the patient populations assessed with these instruments have varied from study to study and the extent of the validation efforts have also varied. These ICU delirium screening instruments differ in the components of delirium they evaluate, in their threshold for diagnosing delirium, and in their ability to be used in patients with impaired vision and hearing and in those requiring intubation.

Table 1 Intensive care unit assessment instruments for delirium

The recent manuscript published in Critical Care by Van Rompaey and colleagues highlights some of the issues surrounding delirium assessment in critical illness and why it is important to think about both the patient population and ICU staff when one chooses a delirium screening instrument [1]. The study compares the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) with the Neelon and Champagne Confusion Scale (NEECHAM) Confusion Scale in a nonintubated, mixed ICU patient population. The authors determined that the incidence of delirium assessed by the two scales was similar. Compared with other studies of ICU delirium that have used the CAM-ICU, the prevalence of delirium in this study was lower and probably related to the absence of intubated patients. The NEECHAM scale allows one to use different cutoff points to categorize patients into delirium, mild confusion, at risk, and normal. As the authors acknowledge, it is unknown whether using an ordinal approach versus a binary one will improve the predictive value of the NEECHAM scale. The CAM-ICU currently gives one a dichotomous outcome for delirium and does not allow one to assess severity.

Ease of administration and acceptance by the nursing and physician staff are critical to any implementation of delirium screening in an ICU setting. Recent literature is emerging on the practicalities of using delirium screening instruments in the ICU. A study by Pun and colleagues demonstrated the ability to implement CAM-ICU screening and documented nursing acceptance of the tool [4]. Devlin and colleagues showed that the Intensive Care Delirium Screening Checklist, along with education supporting its use, improved the ability of both nurses and physicians to detect delirium at the bedside [5, 6]. An ideal delirium screening tool for clinical use must be performed rapidly at the bedside and should not have complicated scales to calculate whether the patient is delirious. In a research setting, investigators will have more time and resources available to calculate delirium scores and look at associations with outcomes – but this is not practical in clinical practice.

While delirium is increasingly being recognized as an important risk factor for adverse outcomes after critical illness, the choice of instrument to screen for delirium depends on the setting (clinical care versus research) and on the patient populations (surgical versus medical, or intubated versus nonintubated). Details about the available ICU delirium screening instruments can be found in a recent review article [3]. The patient population is important when choosing a delirium screening instrument for clinical care or research and also needs to be kept in mind when evaluating the literature on ICU delirium.



Confusion Assessment Method for the Intensive Care Unit


intensive care unit


Neelon and Champagne Confusion Scale.


  1. Van Rompaey B, Schuurmans MJ, Shortridge-Baggett LM, Truijen S, Elseviers M, Bossaert L: A comparison of the CAM-ICU and the NEECHAM Confusion Scale in intensive care delirium assessment: an observational study in non-intubated patients. Crit Care. 2008, 12: R16-10.1186/cc6790.

    PubMed  PubMed Central  Article  Google Scholar 

  2. Jacobi J, Fraser GL, Coursin DB, Riker RR, Fontaine D, Wittbrodt ET, Chalfin DB, Masica MF, Bjerke HS, Coplin WM, Crippen DW, Fuchs BD, Kelleher RM, Marik PE, Nasraway SA, Murray MJ, Peruzzi WT, Lumb PD: Clinical practice guidelines for the sustained use of sedatives and analgesics in the critically ill adult. Crit Care Med. 2002, 30: 119-141. 10.1097/00003246-200201000-00020.

    PubMed  Article  Google Scholar 

  3. Devlin JW, Fong JJ, Fraser GL, Riker RR: Delirium assessment in the critically ill. Intensive Care Med. 2007, 33: 929-940. 10.1007/s00134-007-0603-5.

    PubMed  Article  Google Scholar 

  4. Pun BT, Gordon SM, Peterson JF, Shintani AK, Jackson JC, Foss J, Harding SD, Bernard GR, Dittus RS, Ely EW: Large-scale implementation of sedation and delirium monitoring in the intensive care unit: a report from two medical centers. Crit Care Med. 2005, 33: 1199-1205. 10.1097/01.CCM.0000166867.78320.AC.

    PubMed  Article  Google Scholar 

  5. Devlin JW, Marquis F, Riker RR, Robbins T, Garpestad E, Fong JJ, Didomenico D, Skrobik Y: Combined didactic and scenario-based education improves the ability of intensive care unit staff to recognize delirium at the bedside. Crit Care. 2008, 12: R19-10.1186/cc6793.

    PubMed  PubMed Central  Article  Google Scholar 

  6. Devlin JW, Fong JJ, Schumaker G, O'Connor H, Ruthazer R, Garpestad E: Use of a validated delirium assessment tool improves the ability of physicians to identify delirium in medical intensive care unit patients. Crit Care Med. 2007, 35: 2721-2724. quiz 2725.

    PubMed  Article  Google Scholar 

  7. Hart RP, Levenson JL, Sessler CN, Best AM, Schwartz SM, Rutherford LE: Validation of a cognitive test for delirium in medical ICU patients. Psychosomatics. 1996, 37: 533-546.

    PubMed  CAS  Article  Google Scholar 

  8. Hart RP, Best AM, Sessler CN, Levenson JL: Abbreviated cognitive test for delirium. J Psychosom Res. 1997, 43: 417-423. 10.1016/S0022-3999(97)00140-2.

    PubMed  CAS  Article  Google Scholar 

  9. Ely EW, 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: 2703-2710. 10.1001/jama.286.21.2703.

    PubMed  CAS  Article  Google Scholar 

  10. Ely EW, Margolin R, Francis J, May L, Truman B, Dittus R, Speroff T, Gautam S, Bernard GR, Inouye SK: Evaluation of delirium in critically ill patients: validation of the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). Crit Care Med. 2001, 29: 1370-1379. 10.1097/00003246-200107000-00012.

    PubMed  CAS  Article  Google Scholar 

  11. Bergeron N, Dubois MJ, Dumont M, Dial S, Skrobik Y: Intensive Care Delirium Screening Checklist: evaluation of a new screening tool. Intensive Care Med. 2001, 27: 859-864. 10.1007/s001340100909.

    PubMed  CAS  Article  Google Scholar 

  12. Csokasy J: Assessment of acute confusion: use of the NEECHAM Confusion Scale. Appl Nurs Res. 1999, 12: 51-55. 10.1016/S0897-1897(99)80189-X.

    PubMed  CAS  Article  Google Scholar 

  13. Immers HE, Schuurmans MJ, van de Bijl JJ: Recognition of delirium in ICU patients: a diagnostic study of the NEECHAM confusion scale in ICU patients. BMC Nurs. 2005, 4: 7-10.1186/1472-6955-4-7.

    PubMed  PubMed Central  Article  Google Scholar 

  14. Otter H, Martin J, Basell K, von Heymann C, Hein OV, Bollert P, Jansch P, Behnisch I, Wernecke KD, Konertz W, Loening S, Blohmer JU, Spies C: Validity and reliability of the DDS for severity of delirium in the ICU. Neurocrit Care. 2005, 2: 150-158. 10.1385/NCC:2:2:150.

    PubMed  Article  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Margaret A Pisani.

Additional information

Competing interests

The authors declare that they have no competing interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Pisani, M.A. Delirium assessment in the intensive care unit: patient population matters. Crit Care 12, 131 (2008).

Download citation

  • Published:

  • DOI:


  • Intensive Care Unit
  • Intensive Care Unit Setting
  • Intensive Care Unit Staff
  • Delirium Assessment
  • Intensive Care Unit Environment