Introduction: Ventilator-associated pneumonia (VAP) has been reported to occur in up to 25% of mechanically ventilated patients and can have a mortality ranging up to nearly 50%. Early diagnosis and empiric antibiotic coverage of VAP are crucial to reducing the mortality. Diagnostic tests can aid in the diagnosis of VAP because clinical findings alone are nonspecific. The clinical pulmonary infection score (CPIS) combines clinical, radiographic, physiologic, and microbiological data in a score to use as an indicator of likely VAP. Given the multitude of pulmonary and radiographic anomalies within trauma patients, Culture data is essential for differentiating infective versus non-infective causes of pulmonary dysfunction. Empiric antibiotics are started while awaiting BAL culture data.

We wished to assess the potential impact of empiric antibiotics in trauma patients without pneumonia who then subsequently develop pneumonia during the remainder of their hospital course.

Methods: A retrospective chart review of 436 BAL specimens from 162 patients in our trauma intensive care unit over a 3 year period at a level one trauma center were reviewed. In our trauma intensive care unit once a VAP is suspected patients undergo a bronchoalveolar lavage (BAL) and are started on empiric antibiotic coverage for our institution specific likely organisms. If microbiology data is then negative at 72 hours all antibiotics are then stopped. Pneumonia was definitively diagnosed with microbiology showing >/=104 organisms per ml. Institutional review board approval was obtained.

Results: 14 patients with 23 BAL specimens with initial negative BAL specimen subsequently developed a VAP during the same hospital stay. There was a significant increase in percentage of Enterobacter (21% vs 8%) and Morganella (8% vs 0%) VAP in these patients compared to those whose initial BAL was positive for pneumonia. Furthermore the profile of the top two organisms in each group significantly changed. Enterobacter (21%) and Pseudomonas (17%) were the principal organisms in the initial BAL negative group, while the two predominant strains in the initial positive BAL group were Staphylococcus (21%) and Haemophilus (11%). Interestingly, MRSA remained the third most common organism in both groups. Empiric antibiotics did not induce growth of multi-drug resistant organisms. Interestingly, in the empiric antibiotic, initial negative BAL group, there appears to be a trend towards pan-sensitive E.Coli and pan-sensitive Pseudomonas.

Conclusion: Ventilator associated pneumonia remains a significant cause of morbidity and mortality in mechanically ventilated patients. The diagnosis and treatment of VAP continues to be a challenge. Once clinically suspected empiric coverage decreases morbidity and mortality. No data exists regarding whether this short course of antibiotics without pneumonia impacts the nature of a subsequent pneumonia. Our data demonstrates that patients who receive empiric coverage with no organism growth are susceptible to a significantly different pathogenic profile compared to those who had an initial positive BAL culture. However, this did not induce multi-drug resistance in these organisms.