Ventilator-associated pneumonia in a surgical intensive care unit: epidemiology, etiology and comparison of three bronchoscopic methods for microbiological specimen sampling

Abstract

Background: Ventilator-associated bacterial pneumonia (VAP) is a important intensive care unit (ICU)-acquired infection in mechanically ventilated patients. Early and correct diagnosis of VAP is difficult but is an urgent challenge for an optimal antibiotic treatment. The aim of the study was to evaluate the incidence and microbiology of ventilator-associated pneumonia and to compare three quantitative bronchoscopic methods for diagnosis.

Methods: A prospective, open, epidemiological clinical study was performed in a surgical ICU. In a prospective study, 279 patients admitted to a 14-bed surgical ICU during a 1-year period were evaluated with regard to VAP. Three quantitative culture bronchoscopic techniques for identifying the etiological agent were compared [bronchoalveolar lavage (BAL), protected specimen brush (PSB) and bronchoscopic tracheobronchial secretion (TBS)].

Results: Among 103 long-term ventilated patients, 49 (48%) developed one or more VAPs (a total of 60 VAPs). The incidence was 24 VAPs per 100 ventilated patients or 23 VAPs per 1000 ventilator days. BAL, PSB and TBS with quantitative measurements were equivalent in identifying the bacterial etiology. The VAP was caused predominantly by Staphylococcus aureus in 38% of cases, followed by Pseudomonas aeruginosa in 10%, Haemophilus influenzae in 10% and Klebsiella sp. in 9%. We did not find an increased mortality rate in patients undergoing long-term ventilation who acquired VAP in comparison with patients without VAP.

Conclusion: For the identification of the microbiological etiology of VAP, one of three available bronchoscopic methods analysed by quantitative measurements is sufficient. In our study, quantitative bronchoscopic tracheal secretion analysis was very promising. Before accepting this method as a standard technique, other studies will have to confirm our results.

Figure 1

Times until the start of ventilator-associated pneumonia (always the first episode). Circles, runaway; asterisks, extreme case.