Chapter 12

Many procedures can be performed with the use of local anesthetic alone, instilled at or near the site of surgery. Often this can be done by the surgeon without the use or assistance of an anesthesiologist. Local infiltration is also technically easy to perform and requires minimal postoperative care. Together, these factors contribute to its popularity and nearly ubiquitous application as a means of anesthesia for small minimally invasive procedures and operations. This technique is relatively safe as well, but does require an understanding of basic local anesthetic pharmacology, especially with respect to dosing and toxicity, as well as skill for successful application.

### History of Local Anesthesia

There are several references throughout history of efforts to produce local anesthesia by various means.1 Ancient Egyptians believed that the fat of the crocodile could induce anesthesia if placed on the skin of a patient. The same people also believed that the stone of Memphis could produce local anesthesia if rubbed on the skin with vinegar. Chinese physicians were known to use a mixture of jimson weed, marijuana, deadly nightshade, and mandrake placed into calamus leaves and burned over the operative or painful site to produce anesthesia. In the sixteenth century, Marco Aurelio Severino, an Italian anatomist and surgeon, advocated the use of cold to decrease pain, and this principle was frequently put to use by Napoleon's military surgeons. Other methods of inducing anesthesia locally included electrical current and superficial application of volatile liquids. The first clinical use of a local anesthetic was in 1884, when Austrian ophthalmologist Carl Koller used raw cocaine topically to anesthetize a patient's eye. After this, the use of local anesthetics spread quickly, especially with the synthesis of less toxic compounds such as procaine and lidocaine.2

### General Principles of Local Infiltration Anesthesia

The aim of local infiltration is to anesthetize nerve endings in a finite area of tissue by the injection of local anesthetics nearby. This stands in contrast to peripheral nerve blocks, in which nerve axons are the target and the injection may take place in an area removed from the surgical site (eg, brachial plexus block for hand surgery). The depth of the area to be operated on typically determines the required extent of infiltration. For superficial skin procedures such as suturing of lacerations and skin biopsies, subcutaneous or intradermal infiltration is sufficient. More extensive operations may demand infiltration into muscle, fascia, and other deep tissues.

Two general approaches exist for anesthetizing skin and subcutaneous tissue. The first involves injecting local anesthetic directly into the line of incision and nearby tissues, effectively flooding the individual local nerve endings to produce anesthesia. This can be very effective, but may require large volumes of local anesthetic to achieve complete coverage.

In contrast, field or ring blocks encircle the site of incision with walls of local anesthetic solution through which nerve fibers must pass ...

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