Delirium in the Intensive Care Unit: Occurrence and Clinical Course in Older Patients

OBJECTIVES: To describe the occurrence of delirium in a cohort of older medical intensive care unit (ICU) patients and its short‐term duration in the hospital and to determine the association between preexisting dementia and the occurrence of delirium. DESIGN: Prospective cohort study. SETTING: Fourteen‐bed medical ICU of an 800‐bed university teaching hospital. PARTICIPANTS: One hundred eighteen consecutive patients aged 65 and older admitted to the ICU. MEASUREMENTS: Baseline characteristics were obtained through surrogate interviews and medical chart review. Dementia was determined using two validated surrogate‐rated instruments. Delirium was assessed daily in the ICU using the Confusion Assessment Method (CAM) for the ICU (CAM‐ICU). After discharge from the ICU, patients were followed for up to 7 days using the CAM. RESULTS: Delirium was present in 37 of 118 (31%) patients on admission. Only 45 patients had a normal mental status on admission, of whom 14 (31%) became delirious during their hospital stay. In the post‐ICU period, delirium occurred in 40% of patients. Almost half of patients with delirium in the ICU had persistent delirium in the post‐ICU period. Overall, 83 of 118 (70%) had delirium during hospitalization. Stupor or coma occurred in 44% of the patients overall, and 89% of survivors of stupor/coma progressed to delirium. Patients with dementia were 40% more likely to be delirious (relative risk = 1.4, 95% confidence interval = 1.1–1.7), even after controlling for comorbidity, baseline functional status, severity of illness, and invasive procedures. CONCLUSION: Delirium is a frequent complication in older ICU patients and often persists beyond their ICU stay. Delirium in older ICU persons is a dynamic and complex process. Dementia is an important predisposing risk factor for the development of delirium in this population during and after the ICU stay.