The local anesthetics play a central and frundamental role, for they comprise, probably, the single most widely used group of durgs in the field of plastic surgery. Also many plastic surgical procedures require the use of a vasoconstrictor to reduce operative bleeding under both general and local anesthesia.
Among local anesthetics, lidocaine, introduced by Lofgren in 1948, is one of most widely used local anesthetics and most frequently used for infiltration anesthesia with 0.5% to 1 0%solution. Also eqinephrine is one of the most potent and most useful vasoconstrictors for admixture with thesolution of local anesthetics for infiltration of tissue.
In the clinical practice, it has been said that the concentration of lidocaine and epinephrine should be kept at the minimal level of effectiveness because of the epinephrine performs a dual service when is combined with lidocaine.
In order to clarify the minimum concentration of the lidocaine and epinephrine respectively necessary for adequate duration of anesthesia, with less irritation of local tissue and less bleeding, the clinical observation and animal experiment were undertaken, and the following results were summarized.
The most effective skin blanching by epinephrine was obtained with epinephrine concentration of 1 : 50,000 although some effect was still presented with epinephrine concentration of 1 : 800,000. The onset of maximum skin blanching following the local infiltration of lidocaine with epinephrine(1 : 50,000 to 1 : 400,000) was within 5 minutes and was lasting 20 to 40 minutes.
When the skin incision was made 5 minutes to 15 minutes following local infiltration of epinephrine, the amount of bleeding was markedly decreased and no significant difference in the time of hemostasis was noticed(p〉0.1). Also no significant difference in the time of hemostasis was noticed in the different concentration (1 : 100,000 and 1 : 200,000) of epinephrine(p〉0.1).
The optimum concentration of epinephrine is between 1 : 200,00 to 1 : 400,000 solution and the optimum concentration of lidocaine is 0.5%.
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