Intensive Care Medicine

, Volume 33, Issue 6, pp 1007–1013

Subsyndromal delirium in the ICU: evidence for a disease spectrum

  • Sébastien Ouimet
  • Richard Riker
  • Nicolas Bergeon
  • Mariève Cossette
  • Brian Kavanagh
  • Yoanna Skrobik

DOI: 10.1007/s00134-007-0618-y

Cite this article as:
Ouimet, S., Riker, R., Bergeon, N. et al. Intensive Care Med (2007) 33: 1007. doi:10.1007/s00134-007-0618-y



ICU delirium is common and adverse. The Intensive Care Delirium Screening Checklist (ICDSC) score ranges from 0 to 8, with a score of 4 or higher indicating clinical delirium. We investigated whether lower (subsyndromal) values affect outcome.


600 patients were evaluated with the ICDSC every 8 h.

Measurements and results

Of 558 assessed patients 537 noncomatose patients were divided into three groups: no delirium (score = 0; n = 169, 31.5%), subsyndromal delirium (score = 1–3; n = 179, 33.3%), and clinical delirium (score ≥ 4; n = 189, 35.2%). ICU mortality rates were 2.4%, 10.6%, and 15.9% in these three groups, respectively. Post-ICU mortality was significantly greater in the clinical delirium vs. no delirium groups (hazard ratio = 1.67) after adjusting for age, APACHE II score, and medication-induced coma. Relative ICU length of stay was: no delirium < subsyndromal delirium < clinical delirium and hospital LOS: no delirium < subsyndromal delirium ≈ clinical delirium. Patients with no delirium were more likely to be discharged home and less likely to need convalescence or long-term care than those with subsyndromal delirium or clinical delirium. ICDSC score increments higher than 4/8 were not associated with a change in mortality or LOS.


Clinical delirium is common, important and adverse in the critically ill. A graded diagnostic scale permits detection of a category of subsyndromal delirium which occurs in many ICU patients, and which is associated with adverse outcome.


Delirium Intensive care Screening Outcome Critical care Cognitive abnormalities 

Supplementary material

134_2007_618_MOESM1_ESM.doc (38 kb)
Electronic Supplementary Material (DOC 38K)

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Sébastien Ouimet
    • 1
  • Richard Riker
    • 2
  • Nicolas Bergeon
    • 3
  • Mariève Cossette
    • 4
  • Brian Kavanagh
    • 5
  • Yoanna Skrobik
    • 1
  1. 1.Intensive Care UnitMaisonneuve-Rosemont Hospital and Université de MontréalMontrealCanada
  2. 2.Division of Pulmonary/Critical Care MedicineMaine Medical CenterPortlandUSA
  3. 3.Service of Consultation-Liaison PsychiatryCentre Hospitalier del’Université de MontréalMontrealCanada
  4. 4.Biostatistics ServiceMontreal Heart Institute Coordinating CenterMontrealCanada
  5. 5.Departments of Anesthesia and Critical Care MedicineHospital for Sick Children and University of TorontoTorontoCanada

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