, Volume 33, Issue 6, pp 1007-1013
Date: 03 Apr 2007

Subsyndromal delirium in the ICU: evidence for a disease spectrum

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Abstract

Objective

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.

Patients

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.

Conclusions

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.

This study was partly funded by the FRSQ (Fonds de Recherche en Santé du Québec, Réseau respiratoire).
An erratum to this article can be found at http://dx.doi.org/10.1007/s00134-007-0731-y