Virtually Painless Local Anesthesia: Diluted Lidocaine Proves to Be Superior to Buffered Lidocaine for Subcutaneous Infiltration

October 2012 | Volume 11 | Issue 10 | Original Article | 39 | Copyright © October 2012


Martin Zaiac MD,e Shino Bay Aguilera DO,a Larissa Zaulyanov-Scanlan MD,b Caroline Caperton MD BS MSPH,d Stacy Chimento MDc

aWellington Regional Medical Center/Lake Erie University, Wellington, FL bUniversity of Miami Department of Dermatology, Miami, FL cUniversity of Miami Miller School of Medicine, Department of Dermatology and Subcutaneous Surgery, Miami, FL dUniversity of Miami Miller School of Medicine, Miami, FL eGreater Miami Skin and Laser Center and Florida International University, Miami, FL

table 1
ratio, in which each mL contained 9 mg of sodium chloride and 9 mg of benzyl alcohol.
Solution B (buffered): 5 mL of 8.4% sodium bicarbonate solution and 50 mL of 1% lidocaine and epinephrine in a 1:10 ratio.
Both solutions were kept at room temperature. One dermatologist, M.Z., determined the need for biopsies for each individual, and the same physician then gave each patient subcutaneous injections with a 31-gauge needle that contained 0.3 mL of each solution in two discrete but comparable sites with regard to pain fiber distribution (ie, the left and right cheeks) before either a shave or a punch biopsy. The rate of injection was standardized to the best of the physician's ability, the same injection technique was used for each patient, and the same biopsy technique was then used for both sites on each patient.
The buffered and unbuffered LAs were handed to the physician in a blinded fashion by the same medical assistant who prepared the solutions (ie, neither the physician nor the patients were aware of the content of each solution or the order in which they were administered). In order to ensure consistency, the same number of patients received the buffered solution followed by the unbuffered solution as received the unbuffered solution first followed by the buffered solution. The sequence was randomly assigned using a statistical program (IBM SPSS Statistics 17.0.1) method to maximize internal validity. Between 15 and 20 seconds after the injection of the local anesthetic, patients were asked to rate the pain of the needle insertion and solution infiltration by using a visual analog scale (VAS) from 0 (no pain) to 10 (severe pain) in order to determine which injection solution was the most comfortable (see Figure 1). Biopsies were subsequently performed, and patients were immediately asked to rate the pain experienced during the biopsy alone.
Only peak severity of pain upon injection and upon biopsy was recorded. The duration of pain was not recorded because providing anesthesia during biopsy was deemed most relevant for our study purposes.
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