Abstract
Tumescent anesthesia with highly diluted lidocaine and epinephrine has transformed lipoplasty from bloody hospital surgery to a painless and virtually bloodless office-based procedure. The 10-fold or greater dilution of bottled commercial lidocaine has unearthed a latent subdermal drug storage reservoir, postulated to buffer up to 1 mg of lidocaine per gram of tissue. Tissue-bound lidocaine trapped in this safety net is released slowly but steadily into the systemic circulation for eventual disposition, much like a sustained-release preparation. Because epinephrine profoundly reduces perfusion through the buffer compartment, systemic drug uptake is slowed to the extent that lidocaine release stays apace with the liver's maximum lidocaine clearance capacity of 250 mg/h. Hence, provided the lidocaine is diluted properly, the blood level remains below the 5 μg/ml toxic threshold, despite the administration of many times the conventional upper dose limit of undiluted full-strength lidocaine.
Certain caveats apply when using high-dose lidocaine for tumescent anesthesia. Proper dilution of lidocaine to 0.1% or less (500 to 1000 mg lidocaine per liter solvent), and adding 1 mg fresh epinephrine to each liter, are of the essence. Any decrease in the liver's clearance capacity - as by cytochrome P450 inhibition, functional impairment or chemotherapy - demands a corresponding reduction in the total lidocaine dose. When combining tumescent (diluted) lidocaine with full-strength (undiluted) lidocaine to anesthetize more densely innervated structures such as breast or face, drug dosing must be conservative because of the heightened potential for systemic toxicity from overlapping lidocaine disposition kinetics.
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