This study analyzes the elements that compose the emergency physicians' criterion for selecting elderly patients for intensive care treatment. This issue has not been studied in-depth.

A cross-sectional study was conducted at 4 university teaching hospitals, covering 101 randomly selected elderly patients admitted to emergency department and their respective physicians.

Physicians were asked to forecast their plans for treatment or therapeutic abstention, in the event that patients might require aggressive measures (cardiopulmonary resuscitation or admission to critical care units). Data were collected on physicians' reasons for taking such decisions and their patients' functional capacity and cognitive status (Katz index and Informant Questionnaire on Cognitive Decline in the Elderly).

A logistic regression model was constructed taking physicians' decisions as the dependent variables and adjusting for patient factors and physician impressions.

The functional status reported by reliable informants and the mental status measured by validated instruments were not coincident with the physicians' perception (functional status κ, 0.47; mental status κ, 0.26). A multivariate analysis showed that the age and the functional and mental status of patients, as perceived by the physicians, were the variables that better explained the physicians' decisions.

Physicians' impressions on the functional and mental status of their patients significantly influenced their selection of patients for high-intensity treatments despite the fact that some of these impressions were not correct.