[Comparison of two methods of local anesthetic administration using three phantom tissue models]

Local anesthetic is often administered around surgical wounds to reduce pain. It remains unknown, however, how the agent diffuses into tissue, or whether the method of administration has any impact on the drug diffusion. We evaluated drug-diffusion areas around wounds after administering a dummy agent by needle injection (NI) and direct infiltration (DI) using three phantom tissue models : agar, sponge, and pork rib.

Blue-colored water, a dummy substitute for local anesthetic, was administered in the vicinity of surgical wounds simulated by three tissue models. After the administration, blue-stained cross sectional areas and diffusion capacities were compared.

The stained cross sections of the DI tissue were uniform, while those of the NI tissue were globular and centered around the needle point. The sectional area and diffusion capacity were significantly greater in the DI tissue than in the NI tissue in the agar model, though no significant differences between the administration methods were observed in the other models.

The direct infiltration method is likely to diffuse local anesthetic into tissue more uniformly and more extensively than the needle injection method.