Arthroscopy in septic arthritis. Lidocaine- and iodine-containing contrast media are bacteriostatic.

Puncture of septic foci is usually performed to determine the responsible bacteria. If contrast medium is used instead of saline to rinse the lesion and to withdraw an adequate bacteriologic specimen, the opacification provides valuable information about the extent of the changes. Since lidocaine is usually used as a local anesthetic when patients undergo this procedure, we tested the in vitro antibacterial effects of lidocaine 1%, as well as those of 2 contrast media--meglumine amidotrizoate and metrizamide--on several bacteria. In particular, we looked at the influence of the concentration of inoculum used and the duration of contact before culture. The contrast media did not significantly affect bacterial growth when contact before culture did not exceed 3 hours. In contrast, lidocaine had a significant antibacterial effect, indicating that it should not enter into contact with the bacteriologic specimen.