Impact of appropriateness of initial antibiotic therapy on the outcome of ventilator-associated pneumonia

Objectives: To evaluate the impact of appropriate initial antibiotic therapy (AB) on the outcome of ventilator-associated pneumonia (VAP). Design: Retrospective study (1992-97). Patients and methods: Episodes of VAP diagnosed on both clinical and microbiological criteria after greater than or equal to 48 h of mechanical ventilation (MV). Initial AB was considered appropriate when all significant organisms were susceptible to at least one of the antibiotics started after distal bronchial sampling. Antibiotic treatment was modified within 48 h when susceptibility testing was available. Outcome was recorded at the ICU and hospital discharge. Results: One hundred and eleven patients were included (SAPS II = 48 +/- 18, age = 62 +/- 14 years, mean duration of MV before VAP = 12 +/- 9 days). Initial AB was appropriate in 55 patients (49.5 %). No difference between appropriate initial AB and inappropriate initial AB was found concerning severity indices at the time of VAP diagnosis. ICU length of stay was shorter with appropriate initial AB than with inappropriate initial AB for survivors (12 +/- 11 days vs 20 +/- 24 days, P = 0.01). Crude hospital mortality tended to be lower with appropriate initial AB than with inappropriate initial AB (47.3 % vs 60.7 %, odds ratio = 1.72, 95 % CI = 0.81-3.7). Relative crude mortality reduction with appropriate initial AB was 22 %, 95 % CI = -10 % to 45 %. Conclusion: Inappropriate initial AB of VAP during the first 48 h increased ICU length of stay after VAP diagnosis and tended to increase crude hospital mortality despite equal severity of illness at the time of VAP diagnosis, when compared to appropriate initial AB in a population of 111 ICU patients.