Influence of lung aeration on pulmonary concentrations of nebulized and intravenous amikacin in ventilated piglets with severe bronchopneumonia.
BACKGROUND
Pulmonary concentrations of aminoglycosides administered intravenously are usually low in the infected lung parenchyma. Nebulization represents an alternative to increase pulmonary concentrations, although the obstruction of bronchioles by purulent plugs may impair lung deposition by decreasing lung aeration.


METHODS
An experimental bronchopneumonia was induced in anesthetized piglets by inoculating lower lobes with a suspension of 10(6) cfu/ml Escherichia coli. After 24 h of mechanical ventilation, 7 animals received two intravenous injections of 15 mg/kg amikacin, and 11 animals received two nebulizations of 40 mg/kg amikacin at 24-h intervals. One hour following the second administration, animals were killed, and multiple lung specimens were sampled for assessing amikacin pulmonary concentrations and quantifying lung aeration on histologic sections.


RESULTS
Thirty-eight percent of the nebulized amikacin (15 mg/kg) reached the tracheobronchial tree. Amikacin pulmonary concentrations were always higher after nebulization than after intravenous administration, decreased with the extension of parenchymal infection, and were significantly influenced by lung aeration: 197 +/- 165 versus 6 +/- 5 microg/g in lung segments with focal bronchopneumonia (P = 0.03), 40 +/- 62 versus 5 +/- 3 microg/g in lung segments with confluent bronchopneumonia (P = 0.001), 18 +/- 7 versus 7 +/- 4 microg/g in lung segments with lung aeration of 30% or less, and 65 +/- 9 versus 2 +/- 3 microg/g in lung segments with lung aeration of 50% or more.


CONCLUSIONS
In a porcine model of severe bronchopneumonia, the nebulization of amikacin provided 3-30 times higher pulmonary concentrations than the intravenous administration of an equivalent dose. The greater the lung aeration, the higher were the amikacin pulmonary concentrations found in the infected lung segments.
Elman
Marilia
M
Réanimation Chirurgicale Pierre Viars (Department of Anesthesiology), La Pitié-Salpêtrière Hospital, University of Paris 6, Paris, France.
Goldstein
Ivan
I
Marquette
Charles-Hugo
CH
Wallet
Fréderic
F
Lenaour
Gilles
G
Rouby
Jean-Jacques
JJ
D000583:Amikacin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics*; D001996:Bronchopneumonia / Q000188:drug therapy* / Q000378:metabolism; D007275:Injections, Intravenous; D008168:Lung / Q000378:metabolism* / Q000473:pathology; D009330:Nebulizers and Vaporizers; D012121:Respiration, Artificial; D013552:Swine
D000900:Anti-Bacterial Agents; D000583:Amikacin