LUNG DISTRIBUTION OF INTRATRACHEALLY INSTILLED TC-99M-TOBRAMYCIN-SURFACTANT MIXTURE IN RATS WITH A KLEBSIELLA-PNEUMONIAE LUNG INFECTION

It has been proposed to use pulmonary surfactant as vehicle for intrat racheally instilled antibiotics to achieve a more peripheral and homog eneous antibiotic distribution within the lungs. The present study des cribes a method for labeling tobramycin with technetium (Tc-99m-tobram ycin) and investigates lung distribution of intratracheally instilled Tc-99m-tobramycin with and without the use of surfactant as vehicle in rats infected with Klebsiella pneumoniae. Twenty-four hours after inf ection animals received intratracheally 1 ml/kg of Tc-99m-tobramycin-s urfactant mixture (n = 6), or Tc-99m-tobramycin alone (n = 6). Five mi nutes after instillation animals were killed and lungs were excised, f rozen and cut in 1 mm thick slices. Computer assisted autoradiographs were analyzed to evaluate Tc-99m-tobramycin distribution. Spatial dist ribution of radioactivity represented as the mean fractional area with radioactivity above threshold x 100%, was 47% in the Tc-99m-tobramyci n-surfactant group vs 36% in the Tc-99m-tobramycin (p less than or equ al to 0.05). It is concluded that spreading of intratracheally instill ed Tc-99m-tobramycin through infected lungs is increased when surfacta nt is used as vehicle.