Using Bronchoalveolar Lavage to Distinguish Nosocomial Pneumonia from Systemic Inflammatory Response Syndrome

Abstract

Objective Ventilator-associated pneumonia (PN) is difficult to distinguish from trauma-induced systemic inflammatory response syndrome (SIRS), especially in patients with multiple injuries. Previous work using bronchoscopy and quantitative cultures demonstrated significant bacterial growth in about one-third of patients with clinical evidence of PN. In this prospective study, antibiotic therapy for PN was based solely on quantitative bronchoalveolar lavage (BAL) cultures. Methods Mechanically ventilated trauma patients underwent bronchoscopy with BAL when they developed clinical evidence of PN: fever (temperature > 100.5degreesF), white blood cells > 10,000 or > 10% immature forms, purulent sputum, and new or changing infiltrate on chest roentgenogram. Patients with other infections or those receiving antibiotic for any other reason were excluded. Empiric antibiotic therapy for PN was started at the time of BAL. If the quantitative cultures revealed greater than or equal to10⁵ colonyforming units (CFU)/mL, that patient was defined as having PN and was treated. If the cultures revealed 5 CFU/mL, that patient was defined as having SIRS, and empiric therapy was stopped. Results Forty-three patients (88% blunt, 12% penetrating) underwent bronchoscopy with BAL 55 times. Mean age was 40 and Injury Severity Score was 25. Twenty patients had greater than or equal to10⁵ CFU/mL (47%) and 23 had 5 CFU/mL (53%). There were no differences in age, Injury Severity Score, temperature, white blood cell count, or ventilator days before BAL between groups. Sixty-five percent of those with SIRS improved after empiric therapy was stopped (average 3.3 days), and 35% underwent repeat BAL. Three patients with the initial diagnosis of SIRS developed PN (13% of SIRS). Mortality for PN was 15%, compared with 17% for SIRS; no deaths were related to antibiotic therapy. Conclusions SIRS, which can mimic PN, is common in trauma patients. These entities can be distinguished by bronchoscopy with BAL. Basing antibiotic therapy solely on quantitative BAL cultures is efficacious in trauma patients.