Lidocaine diffusion in five tissue expanders: an in vitro and in vivo study.

Previous work in our laboratory has demonstrated that tissue expanders are permeable to lidocaine. In this two-part study, we assessed the in vitro lidocaine diffusion in the following five common tissue expanders: Dow Corning, McGhan, Cox-Uphoff, Hyer-Schulte (Mentor), and Surgitek. In part 1, we demonstrated that wall thickness appeared to be the major determinant for diffusion. Part 2 reports an in vivo study of lidocaine diffusion from tissue expanders used for breast reconstruction. We initially determined that there is incomplete mixing between the valve and connecting tubing and the contents of the expanders, over the period of 1 week. We subsequently examined the lidocaine diffusion from seven tissue expanders placed in a submuscular position for breast reconstruction. The rate of lidocaine diffusion was highly variable, but on average was about 3% per day.