Determinants of outcome in elderly patients admitted to the intensive care unit

Background: age is thought to be strongly associated with intensive care outcomes, but this relationship may be confounded by many clinical variables. Objectives: to compare clinical characteristics of elderly patients (greater than or equal to65 years) admitted to the intensive care unit (ICU) with those in younger patients and to identify the risk factors which independently could predict mortality in patients aged greater than or equal to75 years. Design: prospective observational cohort study. Setting: medical-surgical ICU in a university hospital. Subjects: 2,067 adult patients admitted to the ICU. Methods: comparison of clinical characteristics of patients divided into groups according to their age. Results: elderly patients comprised 51% of the study population. Compared with younger patients, elderly patients were more severely ill on admission, had shock and renal dysfunction. The presence of infection on admission and the incidence rate of infection acquired during stay in the ICU also significantly increased with age. Hospital mortality increased with age: for patients aged greater than or equal to75 years, it was more than double that of patients aged <65 years (39% versus 19%, P < 0.001). Using multivariate logistic regression analysis we determined the independent risk factors of hospital mortality for the patients aged greater than or equal to75 years: impaired level of consciousness, infection on admission, ICU-acquired infection and severity of illness score. Conclusions: morbidity and mortality in elderly patients admitted to the ICU are higher than in younger patients. The most important factors independently associated with the highest risk of death are the severity of illness, impaired level of consciousness and infection.