The tumescent technique: The effect of high tissue pressure and dilute epinephrine on absorption of lidocaine

Injection of lidocaine into the subcutaneous tissues by the tumescent techn ique results in a delayed absorption of the local anesthetic and has allowe d clinicians to exceed the maximum recommended dose of lidocaine without re ported complications. However, little knowledge exists about the mechanisms that permit such high doses of lidocaine to be used safely with this techn ique. The presence of low concentration epinephrine and the increased tissu e pressure resulting from the tumescent injection have both been implicated as important factors, but neither has been studied in patients whose resul ts were not altered by the variability of the suction procedure. The purpos e of this work was to determine the effect of tissue pressure during tumesc ent injection and presence of low concentration epinephrine on the absorpti on lidocaine from subcutaneous tissues in human volunteers. Twenty healthy female human volunteers were randomized into four study grou ps. After body fat measurements, all subjects received an injection of 7 mg /kg of lidocaine into the subcutaneous tissues of both later al thighs. The injected solution consisted of 0.1% lidocaine and 12.5 meq/liter sodium bi carbonate in normal saline with or without 1:1,000,000 epinephrine. Tissue pressure was recorded during injection using a specially designed double-ba rreled needle. The time required for injection was also recorded. Subjects in group 1 received lidocaine with epinephrine injected by a high-pressure technique. Group 2 subjects received lidocaine with epinephrine injected by a low-pressure technique. Group 3 subjects received lidocaine without epin ephrine injected under high pressure. Group 4 subjects received lidocaine w ithout epinephrine injected under low pressure. Following injection, sequen tial blood samples were drawn over a 14-hour period, and plasma lidocaine c oncentrations were determined by gas chromatography. No suction lipectomy w as performed. Maximum tissue pressure during injection was 339 +/- 63 mmHg and 27 +/- 9 m mHg using high- and low-pressure techniques, respectively. Addition of 1:1, 000,000 epinephrine, regardless of the pressure of injected fluid, signific antly delayed the time to peak plasma concentration by over 7 hours. There was no significant difference in the peak plasma concentration of lidocaine among the foul groups. Peak plasma concentrations greater than 1 mcg/ml we re seen in 11 subjects. Epinephrine (1:1,000,000) significantly delays the absorption of lidocaine administered by the tumescent technique. High pressure generated in the sub cutaneous tissues during injection of the solution does not affect lidocain e absorption. The delay in adsorption may allow time for some lidocaine to be removed fi om the tissues by suction lipectomy. In addition, the study r ise to peak lidocaine concentration in the epinephrine groups may allow the development of systemic tolerance to high lidocaine plasma levels.