A Study for Reducing Pain from Injection of Lidocaine Hydrochloride

Abstract

Local anesthetics produce pain during infiltration into skin. The relationship between local anesthetic-induced pain and pH of the local anesthetic solution has not been fully investigated. Commercial preparation of local anesthetics are prepared as acidic solutions of the salts to promote solubility and stability. And the acidity of local anesthetic solition may be related with the pain during infiltration of the solutione. So, we tried to neutralize the lidocaine hydrochloride solution which is one of the most frequently used local anesthetic agent. Sodium bicarbonate was used for neutralization. Sodium bicarbonate was mixed with lidocaine hydrochloride until the resulting pH of the solution become 7.4 which is identical to the acidity of body fluid. To identify the effect of neutralized lidocaine solution, we had a course of double blind test to 6 volunteers. Both forearm of each volunteer were injected with neutralized lidocaine and plain one, and the degree of pain was estimated by each volunteers. According to subjective description by the volinteers, everyone felt neutralized lidocaine injection site was less painful than plain lidocaine. We concluded that we could reduce pain from infiltration of lidocaine hydrochloride by neutralization of the anesthetic solution with sodium bicarbonate.