A Comparative Analysis of Local Anesthetics: Injection Associated Pain and Duration of Anesthesia

April 2023 | Volume 22 | Issue 4 | 364 | Copyright © April 2023


Published online March 21, 2023

Alex Moses BSa, Skylar Klager SMa, Adam Weinstein MDb,c, Samantha Prabakaran BSa, Naveed Sami MDd, David Weinstein MDd

aUniversity of Central Florida College of Medicine, Orlando, FL
bDepartment of Anesthesiology, Brigham and Women’s Hospital, Boston, MA
cDepartment of Anesthesiology, Harvard Medical School, Boston, MA
dDepartment of Internal Medicine, University of Central Florida College of Medicine, Orlando, FL

Abstract
Background: Local anesthesia administration is frequently the most painful step of dermatologic surgery. Identification of an anesthetic that minimizes infiltration pain and toxicity while maximizing duration of action would improve both patient satisfaction and procedural safety. This study compared eight local anesthetic solutions to identify the composition that minimizes infiltration pain, maximizes duration of effect, and minimizes amount of local anesthetic needed.
Methods: In a double-blinded study, thirty subjects were injected with eight local anesthetic solutions of varied concentrations of lidocaine, epinephrine, benzyl alcohol, and sodium bicarbonate. Infiltration pain was rated by subjects using a visual analog scale and duration of anesthesia was assessed by needle prick sensation every 15 minutes.
Results: Solutions 2, 7, and 8, were significantly less painful (P<0.001), though not statistically different from each other. Two of the three solutions were buffered 10:1 with sodium bicarbonate. Additionally, two of the three contained notably decreased concentrations of lidocaine, 0.091% and 0.083%, than traditionally used in practice. The use of benzyl alcohol did not result in a reduction of reported pain. The duration of action was equal among the solutions regardless of anesthetic concentration.
Conclusions: A solution of 0.091% lidocaine with epinephrine 1:1,100,000 and 0.82% benzyl alcohol reduces medication dose while ensuring maximum patient comfort and, theoretically, increases shelf life. While considered off-label, clinically effective dermal anesthesia may be obtained at a lower concentration of lidocaine and epinephrine than is commonly used, aiding conservative use of local anesthetic, particularly during times of national shortage.

J Drugs Dermatol. 2023;22(4): doi:10.36849/JDD.5183

Citation: Moses A, Klager S, Weinstein A, et al. A comparative analysis of local anesthetics: Injection associated pain and duration of anesthesia. J Drugs Dermatol. 2023;22(4):364-368. doi:10.36849/JDD.5183

INTRODUCTION

Local anesthesia is used in over one-million cutaneous surgeries per year, allowing providers to successfully perform many outpatient and office-setting surgeries.1 However, administration of local anesthesia has drawbacks, including the subjective pain and associated anxiety experienced by patients during administration.2 In addition, there are significant central nervous, cardiovascular, and respiratory system adverse effects associated with local anesthetic toxicity.3

Lidocaine, one of the most commonly administered local anesthetics, is frequently used at a 1% concentration in dermatologic surgery.4 Previous studies show that 0.5% lidocaine with a 1:200,000 epinephrine dose has equivalent anesthetic effects as a dose of 1.0% lidocaine with 1:100,000 epinephrine during Mohs micrographic surgery.5 For skin biopsies, even lower concentrations of 0.1% lidocaine are sufficient.6

Various methods to mitigate the pain of infiltration have been proposed and employed in practice. Buffering of the local anesthetic solution with sodium bicarbonate is one of the most well-known, but benzyl alcohol, a preservative found in bacteriostatic normal saline, also has been shown to diminish the pain of injections.6,7,8 Additionally, given the continued shortage of local anesthetic, judicious use of available local anesthetic is important and identification of the lowest effective dose is crucial.9 This study examined the pain of infiltration and duration of anesthesia of different anesthetic solutions to find the combination that minimizes the amount of local anesthetic used while maximizing patient comfort.
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