Risk factors for early onset pneumonia in trauma patients

The aim of the study was to identify risk factors for early onset pneumonia (EOP) in trauma patients, in order to seek possible intervention strategies.

Participants included 124 consecutive trauma patients admitted to a general intensive care unit (ICU) of a university hospital from December 1990 to February 1992 inclusive.

The following data were prospectively collected for each patient: demographics, severity of trauma according to the abbreviated injury scale (AIS), severity of coma according to the Glasgow coma scale (GCS), presence of pneumothorax, pulmonary contusion, rib fractures, hemothorax, and mechanical ventilation. All patients were monitored daily during the ICU stay for the onset of pneumonia, sepsis syndrome, septic shock, and adult respiratory distress syndrome (ARDS). Criteria for the diagnosis of pneumonia were: core temperature of greater than 38.3 degrees C, a WBC count of 10,000 cells/mm3, purulent tracheobronchial secretions, a worsening of pulmonary gas exchange, and persistent pulmonary infiltrates. All patients with suspected pneumonia underwent quantitative bronchoalveolar lavage (BAL) as well as blood cultures; BAL cultures were considered positive when they showed bacterial growth greater than 1 x 10(5) colony-forming unit (cfu)/ml, or less than 10(5), but with the same microorganism isolated in blood cultures. Pneumonia occurring within the first 96 h after trauma was considered EOP.

A stepwise logistic regression analysis was carried out in order to identify factors independently associated with an increased risk of EOP and late onset pneumonia (LOP).

Overall mortality was 43.5 percent: mortality increased by age and AIS score. Forty one patients (33.1 percent) developed pneumonia: 26 (63.4 percent) were EOP and 15 (36.6 percent) were LOP. In the univariate analysis, an age greater than 40 years, the presence of pulmonary contusion, AIS of more than 4 for thorax and of more than 9 for abdomen, and the absence of mechanical ventilation (MV) during the first 4 days of hospitalization or MV lasting less than 24 h were significantly associated with an increased risk of acquiring EOP. Logistic regression analysis showed that the strongest risk factor for EOP was a combined severe abdominal and thoracic trauma, which increased the risk of EOP by 11 times; an age of more than 40 years and MV of less than 24 h during the first 4 days of hospitalization were also independent risk factors for EOP. Factors associated with LOP were an AIS score of more than 4 for abdomen and a length of MV of more than 5 days.

In a trauma population, a combined severe abdominal and thoracic trauma represents a major risk factor for EOP. Mechanical ventilation administered during the first days after trauma seems to reduce the risk of EOP. As reported in previous studies, mechanical ventilatory support lasting more than 5 days is associated with an increased risk of LOP.