Variability in antibiotic prescribing patterns and outcomes in patients with clinically suspected ventilator-associated pneumonia

Study objectives: To describe the variation in clinical practice strategies for the treatment of suspected ventilator-associated pneumonia (VAP) in a population of critically ill patients; and to determine whether initial empiric treatment with certain antibiotics, monotherapy vs combination antibiotic therapy, or appropriate vs inappropriate antibiotic therapy is associated with survival, length. of hospital stay, or days free of antibiotics. Design: Prospective, observational cohort study. Setting: Medical-surgical ICUs of two university-affiliated tertiary medical centers. Patients: Between May 1, 1998, and August 1, 2000, we screened 7,030 ICU patients and identified 156 patients with clinically suspected VAP. Patients were followed up until death or discharge from the hospital. Results: The mean age was 62 years, mean APACHE (acute physiology and chronic health evaluation) 11 score was 14, and mortality was 34%. Combination antibiotic therapy was used in 53% of patients. Piperacillin-tazobactam, fluoroquinolones, vancomycin, cephalosporins, and aminoglycosides were the most commonly employed antibiotics. Initial empiric antibiotics were deemed appropriate in 92% of patients. The predominant organisms isolated from respiratory secretions included Pseudomonas aeruginosa and Staphylococcus aureus. Patients had lower in-hospital mortality rates if their initial treatment regimen included an antipseudomonal penicillin plus beta-lactamase inhibitor (hazard ratio [HR], 0.41; 95% confidence interval [CI], 0.21 to 0.80; p = 0.009). There was also a strong trend toward reduced mortality rates in patients treated with aminoglycosides (HR, 0.43; 95% CI, 0.16 to 1.11; p = 0.08). Specific antibiotic therapy was not associated with length of hospital stay or days free of antibiotics. Outcomes were similar for patients treated with monotherapy vs combination therapy, and for patients who received initial appropriate vs inappropriate therapy. Conclusions: Patients with clinically suspected VAP who receive initial empiric therapy with antipseudomonal penicillins plus beta-lactamase inhibitors, and possibly aminoglycosides, have lower in-hospital mortality rates when compared with those who are not treated with these antibiotics. These agents should be considered for the initial empiric therapy of VAP.