1721, "loss of feeling," Modern Latin, from Greek anaisthesia "want of feeling, lack of sensation (to pleasure or pain)," from an- "without" (see an- (1)) + aisthesis "feeling," from PIE root *au- "to perceive" (see audience). As "a procedure for the prevention of pain in surgical operations," from 1846.
Total or partial loss of sensation to touch or pain, caused by nerve injury or disease, or induced intentionally, especially by the administration of anesthetic drugs, to provide medical treatment. The first public use of ether to anesthetize a patient in Boston in 1846 initiated widespread acceptance of anesthetics in the Western world for surgical procedures and obstetrics. General anesthesia, administered as inhalation or intravenous agents, acts primarily on the brain, resulting in a temporary loss of consciousness. Regional or local anesthesia affects sensation in a specific anatomic area, and includes topical application of local anesthetics, blocking of peripheral nerves, spinal anesthesia, and epidural anesthesia, which is used commonly during childbirth.