[Microbiological care of ventilated intensive care patients. Feasibility of diagnosis and therapy of pulmonary infection].

Pulmonary infections are the most life-threatening infections in mechanically ventilated patients. Methods to avoid these infections by prophylactic systemic or local administration of antibiotics may promote resistance and selection of distinct groups of pathogens. In mechanically ventilated patients we studied the impact of early diagnosis and specific therapy on the prevention of pulmonary infections. Due to the very short interval between colonization and infection, daily microscopic and microbiologic examinations of tracheobronchial secretions proved to be essential for early and successful therapy and even prevention of pulmonary infections. PATIENTS AND METHODS. The present study comprised a total of 190 patients admitted to the surgical intensive care unit who required mechanical ventilation for a period of at least 48 h: 56 were admitted for multiple trauma; 38 had peritonitis; and the remainder had postoperative complications such as renal failure, cardiac problems, septicemia or pneumonia. Multitraumatized patients (16.5 days) and those with peritonitis (13.8 days) needed the most extensive ventilatory support. After admission antibiotic therapy was started with a second-generation cephalosporin or amoxicillin/clavulanic acid. Further antibiotic treatment was directed strictly against the isolated pathogens. Tracheobronchial secretions were monitored daily by microscopy and cultures. Microscopic evaluation was essential to discriminate between colonization and inflammation, and often indicated the infective agent. If infections were suspected provisional antibiograms were performed on the material. This procedure allowed a specific antibiotic treatment to be initiated 8-12 h later. In patients with pulmonary infections, additional bronchoscopic material was taken in order to correlate these findings with those gained from the tracheobronchial secretions. RESULTS. In 85% of cases massive colonization of the trachea with Pseudomonas aeruginosa, enterobacteria, Staphylococcus aureus or Streptococcus pneumoniae resulted in pulmonary infections 24-48 h later. The reduced virulence of Pseudomonas species (non-aeruginosa) and Acinetobacter species is reflected by an infection rate of 50% and an extended period of time to establish an infection (2-4 days). Only 30% of patients highly contaminated with Candida developed pulmonary infections after 3-6 days. A fair correlation (86%) was found between pathogens isolated in tracheobronchial secretions and bronchoscopic material. In the population studied, 68 patients (35.7%) developed pulmonary infections, 32 of them pneumonia (16.8%), and the others purulent tracheobronchitis with fever. Both groups were treated with antibiotics. Patients with multiple trauma, often accompanied by lung contusion, were most frequently affected. In 59 patients (87%) pulmonary infections were treated successfully by specific antibiotic therapy; 9 patients died so rapidly, that the pulmonary complication could not account for the fatal outcome. In 38 patients with massive contamination of the tracheobronchial system by enterobacteria, Pseudomonas aeruginosa or Staph. aureus, progression from colonization to infection was prevented by early administration of specific therapy. CONCLUSIONS. Because pulmonary infections in most cases arise very soon after pathogens have gained access to the tracheobronchial system daily monitoring of tracheobronchial secretions is required for early initiation of specific therapy.