In-office procedures are increasingly emphasized as a way to reduce referrals, avoid treatment delay, and increase practice revenue. Local analgesia is administered before many in-office procedures such as biopsies, toenail removal, and laceration repair. Skin procedures are performed most commonly; nearly three-quarters (74%) of family physicians (FPs) provided these services in 2018.1 Administration of local anesthetic is often the most feared and uncomfortable step in the entire process.2
Knowledge of strategies to reduce pain associated with anesthetic administration can make a huge difference in the patient experience. This article explores evidence-based techniques for administering a local anesthetic with minimal patient discomfort.
4 factors influence the painof local anesthetic administration
Pain is perceived during the administration of local anesthetic because of the insertion of the needle and the increased pressure from the injection of fluid. The needle causes sharp, pricking “first pain” via large diameter, myelinated A-delta fibers, and the fluid induces unmyelinated C-fiber activation via tissue distention resulting in dull, diffuse “second pain.”
Four factors influence the experience of pain during administration of local anesthetic: the pharmacologic properties of the anesthetic itself, the equipment used, the environment, and the injection technique. Optimizing all 4 factors limits patient discomfort.
Pharmacologic agents: Lidocaine is often the agent of choice
Local anesthetics differ in maximal dosing, onset of action, and duration of effect (TABLE3). Given its ubiquity in clinics and hospitals, 1% lidocaine is often the agent of choice. Onset of effect occurs within minutes and lasts up to 2 hours. Alternative agents, such as bupivacaine or ropivacaine, may be considered to prolong the anesthetic effect; however, limited evidence exists to support their use in office-based procedures. Additionally, bupivacaine and ropivacaine may be associated with greater pain on injection and parasthesias lasting longer than the duration of pain control.4-6 In practice, maximal dosing is most important in the pediatric population, given the smaller size of the patients and their increased susceptibility to toxicity.
Calculating the maximum recommended dose. To calculate the maximum recommended dose of local anesthetic, you need to know the concentration of the anesthetic, the maximum allowable dose (mg/kg), and the weight of the patient.7,8 The concentration of the local anesthetic is converted from percentage to weight per unit volume (eg, 1% = 10 mg/mL; 0.5% = 5 mg/mL). Multiply the patient's weight (kg) by the maximum dose of local anesthetic (mg/kg) and divide by the concentration of the local anesthetic (mg/mL) to get the maximum recommended dose in milliliters. Walsh et al9 described a simplified formula to calculate the maximum allowable volume of local anesthetics in milliliters:
(maximum allowable dose in mg/kg) × (weight in kg) × (1 divided by the concentration of anesthetic).
For delivery of lidocaine with epinephrine in a 50-lb (22.7-kg) child, the calculation would be (7 mg/kg) × (22.7 kg) × (1 divided by 10 mg/mL) = 15.9 mL.
Continue to: The advantages (and misconceptions) of epinephrine