Pain reduction in lidocaine administration through buffering and warming

This study compared the pain from intradermal infiltration of (1) plain lidocaine, (2) warmed lidocaine, (3) buffered lidocaine, and (4) warmed, buffered lidocaine. A randomized, double blind, Latin Square design of 20 volunteers was used. Each volunteer was injected with a series of four test solutions on four separate occasions, for 16 total injections each. Each volunteer served as his or her own control. The mean pain scores for the four solutions were: 44.2 for plain lidocaine, 42.2 for warmed lidocaine, 36.7 for buffered lidocaine, and 29.2 for warmed, buffered lidocaine. Buffered lidocaine was statistically less painful than both plain lidocaine and warmed lidocaine. Warmed, buffered lidocaine was significantly less painful than all other solutions, including buffered lidocaine (P < .005). However, warmed lidocaine did not yield pain scores significantly different from plain lidocaine. In this experimental model, warmed lidocaine was not superior to plain lidocaine, but warmed, buffered lidocaine caused significantly less pain than plain lidocaine, buffered lidocaine, or warmed lidocaine. Thus, there may be benefit from heating the buffered lidocaine now in common clinical use. (Am J Emerg Med 1998;16:353-356. Copyright (C) 1998 by W.B. Saunders Company).