Optimization of lidocaine application in tumescent local anesthesia.

Tumescent local anesthesia is based upon the infusion of large volumes of neutralized anesthetic solutions, mainly lidocaine, at very low concentrations. This results in the paralysis of sensory nerve endings and minute nerve twigs, leading to a reduction in pain. The aim of this study was to assess the safety of lidocaine application in tumescent local anesthesia on different regions of patient's bodies. Measures of safety included the analysis of lidocaine concentrations and its pharmacokinetic parameters. In total, 48 patients were infused with tumescent anesthesia in the hypogastrium, buttocks and thighs, axillae, breasts, trunk, and face and neck areas. Lidocaine was infused in doses ranging from 5.2-40 mg/kg b.w., and in concentrations of 0.05% (hypogastrium, buttocks, thighs) or 0.1-0.15% (axillae, breasts, trunk, face, neck), using a total amount of 300-3200 mg. As the peak lidocaine concentration did not exceed 5 microg/ml (commonly known as the toxic threshold), the results of our study indicate that the doses used (not exceeding 40 mg/kg b.w.) are completely safe for patients undergoing tumescent anesthesia in different body areas. The observation of statistically significant correlations between both the dose and the total amount of lidocaine administered and its peak plasma concentration, together with the lack of correlations between the dose and the amount and the time taken to reach peak concentration, allows the safety of each anesthetic dose to be predicted. An analysis of the heterogeneous dynamics of lidocaine plasma concentration changes in tumescent anesthesia in different body areas indicates that both the rates and the degrees of absorption and elimination depend on the area of infiltration; this is in turn related to the vascularization of any given area. The study of lidocaine concentration and pharmacokinetic parameters also showed that there may potentially be a higher risk of a large anesthetic concentration developing within a short period of time during anesthesia of the upper parts of the body. During tumescent anesthesia, significantly higher plasma concentrations of lidocaine were observed in the face and neck than in the hypogastrium, buttocks and thighs, axillae, breast and trunk 0.5 to 4 h after its infusion. This indicates the need for carefully conducted patient observations immediately after infiltration into the aforementioned areas.