[Amikacin concentrations in lung and serum after single intratracheal administration in men]

This study was designed to assess the diffusion into lung tissue and systemic circulation of amikacin administered endotracheally. Eleven consecutive patients, suffering from lung carcinoma and scheduled for elective pneumonectomy or lobectomy, were included in the study. After induction of anaesthesia and before tracheal intubation, a single 500 mg amikacin dose was administered endotracheally through a catheter whose tip was located 5 cm below the vocal cords. Blood was then collected every 15 min for serum assays, until pulmonary resection had been carried out. Pulmonary concentrations were assessed in a healthy area. Measurements were carried out in duplicate using fluorescence polarizing immunoassay and microbiological methods. Serum peak concentrations were found 105 min after administration (7.97 +/- 5.62 micrograms.ml-1). Six and 12 h after administration, serum concentrations were 3.19 +/- 1.87 and 1.20 +/- 0.67 micrograms.ml-1 respectively. Mean lung concentrations were 1.85 +/- 2.12 micrograms.g-1, with a corresponding serum level of 7.22 +/- 4.36 micrograms.ml-1. However, endotracheal instillation of amikacin provided serum concentrations which, were not high enough for treatment of gram negative pneumonia. Lung concentrations are lower than both serum levels and MIC90 for gram negative bacilli. Moreover, there was a major heterogeneity in serum and lung levels, which seemed to be unpredictable. This was probably due to heterogenous tracheal, bronchial and alveolar absorption. The results obtained in this study with a single dose administration should be reassessed in the light of data obtained with long-term amikacin administration.