Incidence, risk factors and consequences of ICU delirium

Intensive Care Med. 2007 Jan;33(1):66-73. doi: 10.1007/s00134-006-0399-8. Epub 2006 Nov 11.


Objective: Delirium in the critically ill is reported in 11-80% of patients. We estimated the incidence of delirium using a validated scale in a large cohort of ICU patients and determined the associated risk factors and outcomes.

Design and setting: Prospective study in a 16-bed medical-surgical intensive care unit (ICU).

Patients: 820 consecutive patients admitted to ICU for more than 24 h.

Interventions: Tools used were: the Intensive Care Delirium Screening Checklist for delirium, Richmond Agitation and Sedation Scale for sedation, and Numerical Rating Scale for pain. Risk factors were evaluated with univariate and multivariate analysis, and factors influencing mortality were determined using Cox regression.

Results: Delirium occurred in 31.8% of 764 patients. Risk of delirium was independently associated with a history of hypertension (OR 1.88, 95% CI 1.3-2.6), alcoholism (2.03, 1.2-3.2), and severity of illness (1.25, 1.03-1.07 per 5-point increment in APACHE II score) but not with age or corticosteroid use. Sedatives and analgesics increased the risk of delirium when used to induce coma (OR 3.2, 95% CI 1.5-6.8), and not otherwise. Delirium was linked to longer ICU stay (11.5+/-11.5 vs. 4.4+/-3.9 days), longer hospital stay (18.2+/-15.7 vs. 13.2+/-19.4 days), higher ICU mortality (19.7% vs. 10.3%), and higher hospital mortality (26.7% vs. 21.4%).

Conclusion: Delirium is associated with a history of hypertension and alcoholism, higher APACHE II score, and with clinical effects of sedative and analgesic drugs.

MeSH terms

  • Delirium / epidemiology*
  • Female
  • Humans
  • Incidence
  • Intensive Care Units
  • Male
  • Middle Aged
  • Prospective Studies
  • Risk Factors