Towards less painful local anesthesia

Local anesthesia, used for numerous procedures in all fields of medicine, has the drawback of providing significant pain upon injection. Twenty-eight volunteers were asked to compare a subcutaneous injection of plain lidocaine with an injection of lidocaine plus bicarbonate. Twenty-four of the twenty-eight volunteers reported less pain with the buffered lidocaine. The dilution of 1 part bicarbonate to 10 parts plain lidocaine produced a solution that was less painful and better tolerated. The local anesthetic lidocaine is used prior to many minor and major surgical procedures. Although it induces adequate anesthesia, the pain of injection is nearly always of considerable discomfort to the patient. There are numerous factors that have been shown to influence the pain of injection. These include speed of injection, size of needle used, area of the body injected, and simply individual patient characteristics. Since lidocaine comes as an acid solution, local tissue irritation is likely the primary source of pain.