Overview of Local Anesthesia

Local anesthetics are administered via injection or topical application and lead to the loss of sensation in a regional area of the body without any alteration of consciousness. These agents function by blocking peripheral nerve conduction, resulting in sensory impairment and reduced or absent sensations of pain in the affected area. Since the late nineteenth century, local anesthetics have primarily been used during invasive surgical procedures that cause noxious stimulation but do not require muscle relaxation or unconsciousness or during sedations or general anesthetics to help stabilize vital signs by reducing pain. Side effects and complications related to local anesthesia are rare and usually minor, although excessive local anesthetic administration may lead to overdose or systemic toxicity. At a molecular level, the common injectable local anesthetic agents contain three main components which determine the clinical characteristics of each agent: the lipophilic aromatic ring, the intermediate ester or amide linkage, and the hydrophilic terminal amine. There are many local anesthetic agents available which offer a wide variety of clinical effects including differences in potency, onset time, and duration of action. Vasoactive agents (i.e., vasoconstrictors) are used in conjunction with most local anesthetic agents to combat their inherent vasodilatory action. The most commonly used local anesthetic agents include lidocaine, articaine, bupivacaine, mepivacaine, and prilocaine. Ideally, several factors (e.g., the patient’s medical history, the planned surgical procedure, etc.) should be taken into consideration when selecting a specific local anesthetic agent with or without a vasoconstrictor for clinical use.