Anesthesia, loss of sensation, especially the sensation of pain. The loss of sensation following injury or disease is known as pathological anesthesia, but anesthesia, either general or local, can also be drug-induced. General anesthesia is a reversible state of unconsciousness accompanied by muscle relaxation and suppression of reflexes. It is indispensable for many surgical procedures. Injections of short-acting barbiturates such as sodium pentothal are frequently used to speed the onset of anesthesia; inhaled agents, including halothane, ether, nitrous oxide, trichlorethylene, and cyclopropane, are then used to induce and maintain general anesthesia. Local anesthesia is induced by the chemical action of cocaine derivatives like novocaine or lidocaine. Regional anesthesia may be induced by blocking one or more large nerves or spinal nerve roots, as in epidural anesthesia for childbirth.
See also: Anesthesiology.