Fat partitioning of lidocaine in tumescent liposuction

Despite the fact that toxicity is associated with tumescent liposuction, even with large quantities of injected lidocaine, no study to date has quantitated the percentage of injected lidocaine removed by aspiration, or the quantity partitioned into the aspirated fat. The aim of this study was to quantitate, on a mass basis, the percentage of injected lidocaine removed by aspiration both in the fat as well as the fluid component of the aspirate. Eight consecutive patient aspirate samples were analyzed as part of an ongoing study. An in vivo partition coefficient of lidocaine in fat vs. fluid was derived that suggests that the lidocaine diffuses preferentially into the fat matrix prior to suctioning. A distribution factor was derived that relates the effective aspirate concentration to the instilled concentration, allowing an estimate of lidocaine recovery based on the amount injected.