The affective factors on regional anesthesia are lipophilic-hydrophilic balance of local anesthetics, protein binding, hydrogen concentration, structue of intermediate chain, and etc. Local anesthetics in solution exit in a chemical equilibrium between the basic uncharged form(B) and the charged cationic form(BH^(+)) by Henderson-Hasselbalch equation(PH_(a)=PK+log [B]/(BH^(+))). The increasement of uncharged form bring about rapid onset, good quality, and long duration of anesthesia.
Eight patients in group Ⅰ were given 2％ lidocaine21.7ml with 1： 200,000 epinephrine(pH 5.1), and eight patients in group Ⅱ were given 2％ lidocaine 20ml with 1： 200,000 epinephrine added NaHCO₃1. 7ml(pH 7.2) to determine the epidural analgesic effect of the pH-adjusted solution.
The results are summerized as follow
1. The onsets of analgesia and surgical anesthesia were significantly rapid in group Ⅱ.
2. The levels of analgesia were raised more rapidly in group
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