Laughing gas: Nitrous oxide, a gas that can cause general anesthesia. Nitrous oxide is sometimes given in the company of other anesthetic agents but it is never used today as the only anesthetic agent because the concentration of nitrous oxide needed to produce anesthesia is close to the concentration that seriously lowers the blood oxygen level and creates a hazardous state of hypoxia.
Nitrous oxide figured in the history of anesthesiology. In 1840 a dentist named Horace Wells had the idea that, with the recently discovered "exhilarating or laughing gas", teeth might be extracted without pain. Under its influence he had one of his own teeth pulled in 1844 and afterwards frequently used nitrous oxide in his practice. At the Massachusetts General Hospital, Wells gave a demonstration with a patient. Things did not go too well. The patient suffered great pain. Wells became depressed, addicted (to chloroform, another anesthetic agent) and in 1848 committed suicide.