Risk and Prognostic Factors of Ventilator-Associated Pneumonia
Objective: To assess the risk and prognostic factors of ventilator-associated pneumonia in trauma patients, with an emphasis on the inflammatory response.
Design: Case-control study.
Setting: Trauma intensive care unit.
Patients: Of 190 consecutive mechanically ventilated patients, those with microbiologically confirmed pneumonia (n = 62) were matched with 62 controls without pneumonia.
Interventions: None.
Measurements and Main Results: Clinical, microbiological, and outcome variables were recorded. Cytokines were measured in serum and blind bronchoalveolar lavage specimens at onset of pneumonia. Multivariate analyses of risk and prognostic factors for ventilator-associated pneumonia were done. Increased severity of head and neck injury (odds ratio, 11.9; p < .001) was the only independent predictor of pneumonia. Among patients with pneumonia, serum levels of interleukin-6 (p = .019) and interleukin-8 (p = .036) at onset of pneumonia were higher in nonresponders to treatment. Moreover, serum levels of tumor necrosis factor-α (p = .028) and interleukin-6 (p = .007) at onset of pneumonia were higher in nonsurvivors. Mortality in the intensive care unit was 23% in cases and controls. Nonresponse to antimicrobial treatment (odds ratio, 22.2; p = .001) and the use of hyperventilation (p = .021) were independent predictors of mortality in the intensive care unit for patients with pneumonia.
Conclusions: Severe head and neck trauma is strongly associated with ventilator-associated pneumonia. A higher inflammatory response is associated with nonresponse to treatment and mortality among patients with pneumonia. Although pneumonia did not influence mortality, nonresponse to treatment independently predicted mortality among these patients.

Severely injured trauma patients frequently require intensive care unit (ICU) admission and mechanical ventilation (MV) and therefore are at risk for developing hospital-acquired pneumonia. Even though there is some controversy about whether ventilator-associated pneumonia (VAP) is associated with higher mortality in this specific setting, studies have shown that VAP increases the length of ventilation and ICU stay.

Some studies have previously tried to identify risk factors for posttraumatic pneumonia, with the rationale of preventing pneumonia and improving outcome. However, not all these studies used diagnostic criteria based on systematic microbiological examination, which could interfere with the interpretation of the results, and most were cohort studies. We are not aware of any case-control study that has prospectively addressed this issue.

Trauma patients have an increased systemic inflammatory response, which is initiated soon after the trauma. However, few studies have evaluated the relationship of the systemic inflammatory response in this specific group of patients with regard to the development and prognosis of VAP. In a previous study of patients, mainly nontraumatic with nonresponding ICU-acquired pneumonia, we found that increased serum levels of proinflammatory cytokines were associated with nonresponse to treatment and mortality.

The aim of the present study was to identify the risk and prognostic factors of VAP among severely ill trauma patients, with use of a case-control design. Special emphasis was given to assessment of the patterns of local and systemic inflammatory response in a subset of these patients.