Prior functional status is a predictor of outcome in critically ill patients

Introduction: With the aging of the population, many disabled and elderly patients are admitted to the ICU for management of acute conditions. In this prospective study we tested whether prior impaired functional capacity is an independent prognostic index. Setting: a 12 bed general ICU of an 1100 bed tertiary university hospital Methods: Over a period of 6 months, we studied prospectively all patients who were not gainfully employed prior to the onset of the acute condition that mandated ICU admission. Data was collected from next of kin during the first debriefing session with the unit attending. The structured questionnaire included demographic data, Katz's physical activities of daily living(pADL) scores, a global assessment of congnitive function, and regular indoor and outdoor activities. Patients were followed to discharge from the hospital. Actual hospital survival was compared to APACHE II predicted survival. Non-parametric tests (Kruskal-Wallis)were used for statistical analysis. Results: 97 patients were analyzed. Mean age was 73(36-94). 55% were men. 65% were surgical patients. Mortality was 50.5%, much higher than the APACHE II predicted mortality of 31.4±2.3% (p< 0,01)for the group and the unit mortality during the same time period (12.9%). Of all the variables tested, only pADL's and walking habits were significant predictors of hospital mortality. 68% of the 25 patients with an abnormal aADL score died Vs. 44% of the 72 patients with normal pADL scores (p= 0.04). The mortality in both groups was higher than the APACHE II predicted mortality (38±4% and 29±3% respectively). Walking habits also correlated with survival, but the correlation disapeared with stratification by pADL scores. Proxy assessment of cognitive function and the will to live had no effect on survival. Conclusions: We have identified a group of patients who have a poor prognosis, regadless of cause of ICU admission. Within this group of very sick patients, patients with impaired ability to do pADL's are at a particularly high risk. Although further research is needed to explain all the excess mortality in this group, this study validates Katz's pADL scores as a holistiic prognostic tool in the ICU.