Addition of sodium bicarbonate to lidocaine decreases the duration of peripheral nerve block in rat. (Harvard Medical School, Boston, MA) Anesthesiology 2000;93:1045–1052.

Abstract

This study evaluated the effect of adding sodium bicarbonate to lidocaine with and without epinephrine versus equivalent alkalinization by sodium hydroxide (NaOH) on onset, degree, and duration of peripheral nerve block. The study was broken up into two parts. Part I examined alkalinization by sodium bicarbonate versus NaOH to pH 7.8 on 0.5% lidocaine, with and without epinephrine prepared from crystalline salt. Part II examined 0.5% and 1.0% commercial lidocaine solutions, with and without epinephrine, either unalkalinized or alkalinized with sodium bicarbonate or NaOH. The study concluded that with 1% commercial lidocaine without epinephrine, sodium bicarbonate decreases the degree and duration of the block. However, in solutions with epinephrine, sodium bicarbonate hastens onset, without effecting degree or duration.Comment by Octavio Calvillo, M.D., Ph.D. There is evidence that adding sodium bicarbonate to lidocaine without epinephrine improves the quality of epidural block, whereas adding sodium bicarbonate to lidocaine with epinephrine does not. The addition of 8.4% sodium bicarbonate to 2% lidocaine without epinephrine was shown to decrease the onset time and enhance the depth of the epidural block. When bicarbonate was added to 2% lidocaine with epinephrine neither onset time nor depth of the epidural block was affected. Most investigators have used epidural block as their paradigm. The authors in this study used the sciatic nerve block of the rat.