Characteristics associated with delirium in older patients in a medical intensive care unit

Background: Delirium is a highly prevalent disorder among older patients in the intensive care unit. Methods: We performed a prospective cohort study of 304 patients 60 years or older admitted from September 5, 2002, through September 30, 2004, to a 14-bed ICU in an urban university teaching hospital. The main outcome measure was ICU delirium that developed within 48 hours of ICU admission. Patients were assessed for delirium with the Confusion Assessment Method for the ICU and medical record review. Risk factors for delirium were assessed on ICU admission by interview with proxies and medical record review. A model was developed using multivariate logistic regression and internally validated with bootstrapping methods. Results: Delirium occurred in 214 study participants (70.4%) within the first 48 hours of ICU admission. In a multivariate regression model, 4 admission risk factors for delirium were identified. These risk factors included dementia (odds ratio [OR], 6.3; 95% confidence interval [CI], 2.9-13.8), receipt of benzodiazepines before ICU admission (OR, 3.4; 95% CI, 1.6-7.0), elevated creatinine level (OR, 2.1; 95% CI, 1.1-4.0), and low arterial pH (OR, 2.1; 95% CI, 1.1-3.9). The C statistic was 0.78. Conclusions: Delirium is frequent among older ICU patients. Admission characteristics can be important markers for delirium in these patients. Knowledge of these admission risk factors can prompt early correction of metabolic abnormalities and may subsequently reduce delirium duration.