ALT The left-hand column outlines a brief history of anesthetics with relevant chemical structures. Nitrous oxide and diethyl ether were the earliest anesthetics, and the former is still in use today. Cocaine was the first local anesthetic, but lidocaine is now the most widely used. Halogenated hydrocarbons and ethers are the most commonly used inhaled anesthetics today, while propofol is the most commonly used intravenous general anesthetic.

The right-hand column of the graphic starts by highlighting the four categories of anesthesia: general (the patient is unconscious), local (a small area is numbed), regional (a larger area of the body is numbed), and sedation (the patient is drowsy and relaxed but not unconscious).

Finally, the graphic discusses how anesthetics work. Local anesthetics block sodium ion channels to halt nerve impulses; a diagram of a blocked ion channel is shown. General anesthetics block nerve transmission at synapses, but exactly how they do this is still not known.