Bacteremia and Ventilator-Associated Pneumonia: A Marker for Contemporaneous Extra-Pulmonic Infection

Abstract

Ventilator-associated pneumonia (VAP) is a well-known complication of mechanical ventilation in severely injured patients. A subset of patients with VAP develop an associated bacteremia (B-VAP), but the risk factors, microbiology, morbidity, and mortality in this group are not well described. The goal of this study was to examine the incidence, predictors, and outcome of B-VAP in adult trauma patients. We conducted a retrospective review of trauma patients who developed VAP or B-VAP from January 2007 to December 2009 at a single, university-affiliated medical center. Ventilator-associated pneumonia was defined as a clinician-documented instance of VAP together with confirmed positive respiratory cultures (bronchoalveolar lavage [BAL] fluid specimen with ≥10(4) colony forming units (CFU)/mL or tracheal aspirate with moderate-to-many organisms and polymorphonuclear neutrophils [PMN]). Bacteremia associated with VAP (B-VAP) was defined as the blood culture of an organism that matched the pulmonary pathogen in a case of VAP. We reviewed the demographic data, injury severity, transfusion data, and microbiology of patients who developed VAP and B-VAP. Outcome data included the number of days of care in the intensive care unit (ICU) and hospital length of stay, number of days of mechanical ventilation, and survival. A Student t-test, χ(2) test, or logistic regression was used as appropriate for data analysis. During the 36-mo period of the study, 4,018 adult patients were admitted to the hospital. Ventilator-associated pneumonia was diagnosed in 206 (5%) of these patients, and 26 of these latter patients (13%) had an associated bacteremia. The mean time from admission to the development of VAP was 5 d (95% CI 4.6-5.8). Patients who had B-VAP received significantly more units of red blood cell concentrates (PRBC) than those who did not have B-VAP (23 units vs. 9 units of PRBC, respectively, p<0.05). Patients with B-VAP also had higher rates of simultaneous non-pulmonary infections than those with VAP alone (69% vs. 38%, respectively), a greater number of days of mechanical ventilator support (24 d vs. 14 d, respectively, p<0.05), a greater number of days in the ICU (26 d vs. 17 d, respectively, p<0.05), and a greater hospital length of stay (50 d vs. 30 d, respectively, p<0.05). Patients with B-VAP showed a trend toward lower survival than those without B-VAP, but B-VAP was not an independent predictor of mortality. Trauma patients with B-VAP have a similar mortality but greater morbidity than those with VAP alone. The number of PRBC received is the most significant risk factor for developing B-VAP. More than two-thirds of patients with B-VAP have contemporaneous extra-pulmonic infections. Trauma patients with B-VAP may benefit from increased surveillance for additional concomitant infections and from more aggressive empiric antimicrobial coverage.