Abstract
Antimicrobial action of lidocaine solutions was studied as part of the serial transbronchial bacteriological culture study using the flexible fiberoptic bronchoscope. Clinical strains of E. coli, Klebsiella, Sta. aureus, Serratia, Str. hemolyticus, Str. viridans, Str. pneumoniae, Ps. aeruginosa, Mycobacterium tuberculosis and atypical mycobacterium were all used for these experiments. The colony count of these microorganisms were distributed between 8×106/ml to 68×1010/ml. Each lidocaine solution was prepared from 4% xylocaine containing methylparaben, and pure lidocaine powder. The hydrogen ion concentration of each solution was kept around 6.4 by using phosphate buffer system. Conclusive results were obtained and the following cautions should be observed, when transbronchoscopic bacteriological culture is performed under local anesthesia using lidocaine solution. The antimicrobial action of lidocaine solution was bacteriostatic and this inhibitory action was proportional to the mixing time of the lidocaine solution and the bacterial growth. However, at a concentration of 8, 000-24, 000γ/ml or more, it changed to bacteriocidal, so possibly a smaller amount, say 2% lidocaine solution, should be used instead of the usual 4% solution. Take the bacterial specimens and cultivate them as quickly as possible. If this is not done, general bacterial specimens must be kept in an incubator. For acid fast bacterial culture specimens must be kept in a refrigerator. In any case, both specimens should be cultivated within one hour. In some cases, airway lavage with normal saline solution prior to taking a bacterial specimen is advisable for the lidocaine dilution.
