Local anesthesia may be defined as a loss of sensation in a circumscribed area of the body due to a depression of excitation in nerve endings or an inhibition of the conduction process in peripheral nervous tissue. This localized state of anesthesia may be produced by such different means as mechanical trauma, low temperature, anoxia, and a variety of chemical irritants. In general, only substances that produce a transient and completely reversible state of insensibility are employed in clinical practice. Neurolytic agents such as alcohol or phenol may be useful to induce a relatively permanent state of anes-thesia in patients with intractable pain.
