Context In the intensive care unit (ICU), delirium is a common yet underdiagnosed
form of organ dysfunction, and its contribution to patient outcomes is unclear.
Objective To determine if delirium is an independent predictor of clinical outcomes,
including 6-month mortality and length of stay among ICU patients receiving
Design, Setting, and Participants Prospective cohort study enrolling 275 consecutive mechanically ventilated
patients admitted to adult medical and coronary ICUs of a US university-based
medical center between February 2000 and May 2001. Patients were followed
up for development of delirium over 2158 ICU days using the Confusion Assessment
Method for the ICU and the Richmond Agitation-Sedation Scale.
Main Outcome Measures Primary outcomes included 6-month mortality, overall hospital length
of stay, and length of stay in the post-ICU period. Secondary outcomes were
ventilator-free days and cognitive impairment at hospital discharge.
Results Of 275 patients, 51 (18.5%) had persistent coma and died in the hospital.
Among the remaining 224 patients, 183 (81.7%) developed delirium at some point
during the ICU stay. Baseline demographics including age, comorbidity scores,
dementia scores, activities of daily living, severity of illness, and admission
diagnoses were similar between those with and without delirium (P>.05 for all). Patients who developed delirium had higher 6-month
mortality rates (34% vs 15%, P = .03) and spent 10
days longer in the hospital than those who never developed delirium (P<.001). After adjusting for covariates (including age,
severity of illness, comorbid conditions, coma, and use of sedatives or analgesic
medications), delirium was independently associated with higher 6-month mortality
(adjusted hazard ratio [HR], 3.2; 95% confidence interval [CI], 1.4-7.7; P = .008), and longer hospital stay (adjusted HR, 2.0;
95% CI, 1.4-3.0; P<.001). Delirium in the ICU
was also independently associated with a longer post-ICU stay (adjusted HR,
1.6; 95% CI, 1.2-2.3; P = .009), fewer median days
alive and without mechanical ventilation (19 [interquartile range, 4-23] vs
24 [19-26]; adjusted P = .03), and a higher incidence
of cognitive impairment at hospital discharge (adjusted HR, 9.1; 95% CI, 2.3-35.3; P = .002).
Conclusion Delirium was an independent predictor of higher 6-month mortality and
longer hospital stay even after adjusting for relevant covariates including
coma, sedatives, and analgesics in patients receiving mechanical ventilation.