Background: To identify nosocomial infection risk factors in an intensive care unit and construct a predictive model that will enable future risk-adjusted comparisons of infection incidences.
Patients and methods: Prospective surveillance of pneumonia, bacteremia and urinary tract infections in intensive care unit patients. All patients (n = 944) admitted to the intensive care unit for at least 24 h were followed daily in a tertiary level hospital. Variables measuring extrinsic as well as intrinsic risk factors for nosocomial infections were collected from each patient during their intensive care unit stay and the Cox proportional hazards multivariable technique was applied to identify the variables mostly associated with infection in our hospital.
Results: The main risk factors identified for pneumonias were intrinsic. The hazard ratios (HR) of two extrinsic risk factors were noteworthy: mechanical ventilation (HR = 7.51; 95% CI = 2.95-19.13) and sedation (HR = 2.01; 95% CI = 1.14-3.56). The extrinsic factors associated with bacteremias were, the sum of extrinsic risk factors (HR = 1.52; 95% CI = 1.17-1.97) and having a tracheostomy (HR = 3.61; 95% CI = 1.99-6.56). The urinary tract infections were negatively associated with the administration of antibiotics prior to infection onset (HR = 0.41; 95% CI = 0.21-0.78) and the male sex (HR = 0.40; 95% CI = 0.22-0.75). Conversely, urinary tract infections were positively associated with the presence of cancer (HR = 2.70; 95% CI = 1.03-7.11) and the APACHE II index (for every 5 units of increase of the APACHE II index, HR = 1.39; 95% CI = 1.09-1.79).
Conclusions: The most important risk factors identified for pneumonias and urinary tract infections in intensive care unit patients were endogenous, whereas they were exogenous for bacteremias.