Reliability of mini-bronchoalveolar lavage for the measurement of epithelial lining fluid concentrations of tobramycin in critically ill patients

Objective: To evaluate the reliability of mini- bronchoalveolar lavage ( mini- BAL) for the measurement of tobramycin concentrations in epithelial lining fluid ( ELF) in comparison with conventional bronchoscopic bronchoalveolar lavage ( BAL). Design: Prospective, open- label study. Setting: An intensive care unit and research ward in a university hospital. Patients: Twelve critically ill adult patients with ventilator- associated pneumonia ( VAP). Interventions: All subjects received intravenous infusions of tobramycin 7 - 10 mg/ kg once daily. After 2 days of therapy, the steady-state serum and ELF concentrations ( obtained from BAL and mini- BAL) of tobramycin were determined by means of high- performance liquid chromatography. Measurements and results: We observed poor penetration of tobramycin in ELF of approximate to 12% with ELF peak concentrations of approximate to 3 mg/ l with both methods. Good agreement in Bland - Altman analysis ( mean +/- SD bias = 0.04 +/- 0.38 mg/ l) was observed between the two methods of sampling. Conclusion: Our results suggest that tobramycin 7 - 10 mg/ kg once daily in critically ill patients with VAP might provide insufficient lung concentrations in the case of difficult- to- treat pathogens. Besides, mini- BAL, which is simple, non- invasive and easily repeatable at the bedside, appears to be a reliable method for the measurement of antibiotic concentrations in ELF in comparison with bronchoscopic BAL in critically ill patients with VAP.