Predictive Factors of Good Pulmonary Penetration of Antibiotics : AntiBiotics Dosage in Broncho-Alveolar Lavage

To check if pulmonary concentrations of antibiotic are enough we will measure antibiotic concentration in the broncho-alveolar lavage (BAL). This technique which is clinically relevant and reliable could determinate the pulmonary diffusion level for antibiotics by calculating the ratio between plasmatic and intra-alveolar antibiotic concentration. This ratio will be correlated with potential limitation factors of pulmonary diffusion as respiratory diseases (COPD, cystic fibrosis, fibrosis…), sepsis, hypoalbuminemia. We have chosen to study the beta lactamin antibiotics because they are the most frequently used in pneumonia. Moreover, the beta lactamins pulmonary diffusion is likely to be the lowest. Finally, for patients with a known pathogen, we will divide this pulmonary concentration with minimal inhibitory concentration (MIC). Indeed, in severe pneumonia, to be sure of bactericidal activity, a pulmonary concentration of beta lactamines should be always higher than 4 to 5 times MIC.