The effectiveness of local anesthetics is improved by the addition of a vasoconstrictor which increases duration of action and decreases both systemic toxic reactions and local bleeding. Epinephrine, the standard drug for vasoconstriction, has some limitations due to potential dose-related cardiac and local toxic effects. The authors examined the minimal effective epinephrine concentration required for maximal cutaneous vasoconstriction in the human subject so as to limit potential dose-related side effects. In a randomized, double-blinded prospective study, 23 patients undergoing head and neck surgical procedures under general anesthesia were enrolled to quantify the effect of subdermal infiltration of 1% lidocaine with epinephrine at varying concentrations on local cutaneous bloodflow utilizing laser Doppler flowmetry. A comparison of the onset of vasoconstriction and magnitude of diminished bloodflow was made for several commonly used concentrations of epinephrine, with 1% lidocaine and normal saline serving as controls. There were no significant differences (P >.05) between epinephrine concentrations of 1:400,000, 1:200,000, 1:100,000, and 1:50,000 when examining onset and magnitude of vasoconstriction.
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