A case-control study on risk factors for early-onset respiratory tract infection in patients admitted in ICU

BACKGROUND: Respiratory tract infections are common in intensive care units (ICU), with incidences reported from 10 to 65%, and case fatality rates over 20% in pneumonia. This study was designed to identify risk factors for the development of an early onset respiratory tract infection (ERI) and to review the microbiological profile and the effectiveness of first intention antibiotic therapy. METHODS: Case-control, retrospective clinical study of the patients admitted to the Intensive Care Unit (ICU) of our hospital, a teaching and tertiary care facility, from January to September 2000 who had a respiratory tract infection diagnosed in the first 5 days of hospital stay. RESULTS: Of the 385 patients admitted to our unit: 129 (33,5%) had a diagnosis of ERI and 86 patients were admitted to the control group. Documented aspiration (adjusted OR = 5,265; 95% CI = 1,155 – 24,007) and fractured ribs (adjusted OR = 12,150; 95% CI = 1,571 – 93,941) were found to be independent risk factors for the development of ERI (multiple logistic regression model performed with the diagnostic group as dependent variable and adjusted for age, sex, SAPS II, documented aspiration, non-elective oro-tracheal intubation (OTI), fractured ribs, pneumothorax and pleural effusion). A total of 78 organisms were isolated in 61 patients (47%). The normal flora of the upper airway (Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenza and Moraxella catharralis) accounted for 72% of all isolations achieved, polimicrobian infections were responsible for 25% of all microbiological documented infections. First intention treatment was, in 62% of the patients, the association amoxacillin+clavulanate, being effective in 75% of the patients to whom it was administered. The patients with ERI needed more days of OTI (6 vs 2, p < 0,001) and mechanical ventilation (6 vs 2, p < 0,001) and had a longer ICU (7 vs 2, p < 0,001) and hospital length of stay (17 vs 11, p = 0,018), when compared with controls. CONCLUSION: In this study documented tracheobronchial aspiration and fractured ribs were identified as independent risk factors for ERI. Microbiological profile was dominated by sensitive micro-organisms. The choice amoxacilin+clavulanate revealed to be a good option with an effectiveness rate of 77% in the patients in whom it was used.