More interventions do not necessarily improve outcome in critically ill patients

Objective. The organizational structure of health care facilities has been shown to affect outcome in critically ill patients. We evaluated the association between structures, treatments and outcomes in a large cohort of critically ill patients. Design. Prospective multicentre cohort study. Patients and setting. A total of 26,186 patients consecutively admitted to 31 intensive care units (ICUs) in Austria from January 1998 through December 2000. Measurements and results. The ICUs were divided into three groups according to the size and function of the hospital: community hospitals and specialized trauma centers (group A); central referral hospitals (group B); and teaching hospitals (group C). Group C patients exhibited a significantly higher risk-adjusted mortality (O/E ratio). Although severity of illness at admission in groups B and C was similar, group C patients received significantly more invasive diagnostic and therapeutic interventions throughout their ICU stay: For 7 of 10 invasive interventions identified, odds ratios for group C vs group B patients were significantly increased, even after adjustment for age, gender, severity of illness and reason for admission (odds ratios 1.2-13.1; all 95% CIs >1). Risk-adjusted multivariate analysis confirmed that six of these invasive interventions were independently associated with mortality. Furthermore, nurse-to-patient ratios did not differ between groups, leading to a significantly increased nursing workload in group C ICUs. Conclusions. Several invasive interventions were independently associated with increased mortality. Our results provide strong evidence that this association was responsible in part for the increased risk-adjusted mortality in group C patients.