Local anesthetics refer to drugs that act on local nerve endings or nerve trunks and can temporarily block the transmission of sensory (afferent) impulses and make local pain disappear temporarily. The generation and conduction of nerve impulses depend on a series of changes in ion permeability of nerve cell membrane. At rest, calcium ions combine with phospholipid protein on the membrane to prevent the inflow of sodium ions. When excited, calcium ions leave the binding point, and sodium ions flow in in large quantities, resulting in action potentials, thus generating nerve impulses and conduction. The role of local anesthetics is to firmly occupy the binding point of calcium ions and prevent the influx of sodium ions, resulting in the inability to generate action potentials, blocking nerve conduction and producing local anesthesia. Local anesthesia is usually divided into the following categories:

(1) surface anesthesia. The anesthetic is sprayed or sprayed on the mucosal surface to anesthetize the submucosal sensory nerve endings.

(2) Infiltration anesthesia. The liquid medicine is injected into subcutaneous or submucosal tissues, and the liquid medicine diffuses and infiltrates sensory nerve endings in the operation department to produce anesthesia.

(3) conductive anesthesia. Inject liquid medicine around nerve trunk, nerve plexus or ganglion to anesthetize the area controlled by nerve.

(4) Epidural anesthesia. Inject the liquid medicine into the epidural space to block the spinal nerve from coming out of the epidural space, so as to anesthetize the hindquarters. The commonly used local anesthetics in clinic are procaine hydrochloride (novocaine hydrochloride), lidocaine (silocaine), tetracaine (dicaine, Toracca) and cocaine (cocaine).