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.

Effects of preoperative medications on gastric pH, volume, and flora.

Aspiration of acid gastric juice poses a potential threat during operations. Many anesthesiologists use a variety of agents aimed at decreasing gastric volume and/or acidity. The effect of three agents on gastric volume, pH, and flora, and the effect of cefazolin on gastric flora in morbidly obese patients were studied. Cefazolin did not sterilize the gastric lumen. Almost one-half of patients not treated with an H2 blocker had a pH below 2.5 and a gastric volume of 20 ml or more. Five had both a low pH and significant volume and, thus, the potential for lethal aspiration. Two doses of cimetidine, 300 mgm orally, or of ranitidine, 150 orally, the evening before and the morning of operation decreased gastric volume and raised pH reliably to a level that should be protective from fatal aspiration. However, gastric cultures after these drugs were positive 86% of the time with a larger variety of organisms than in the untreated stomachs. Metoclopramide failed to decrease gastric volume or raise pH. Transoperative cefazolin was used in all patients. Clinical infection was not a problem.