NITROUS OXIDE.—Nitrous oxide (ni trogen monoxide, protoxide of nitrogen, laughinggas) is a colorless, transparent gas of neutral reaction, sweetish taste, and almost odorless. It may be made by heating ammonium nitrate in a flask or retort, which decomposes it into nitrous oxide gas and water. To free it from any trace of acid or nitric oxide the gas should be passed through a solution of potassium hydrate, then through a solu tion of ferrous stilphate, and finally be left in an inverted jar over water for twenty-four bours. The gas may be liquefied by pressnre: a fact that enables it to be carried about in cylinders. It is readily converted into the gaseous state when wanted by allowing it to escape into a rubber bag, the relief from pressure in ducing the change of state from liquid to gas. Nitrous-oxide gas was discovered by Priestly. Its amesthetic properties were first recognized by Sir Humphry Davy. It was first used practically by Horace Wells, a dentist of Hartford, Conn.
Physiological Action.— Hare and Cerna summarize the physiological ac tion of nitrous-oxide gas as follows: It causes a rise of arterial pressure, fol lowed by a fall, the rise being due to vasomotor stimulation and the fall to vasomotor palsy. There is also marked slowing of the heart, which is believed to be due to stimulation of the inhibi tory centre in the medulla oblongata. Finally, the slow pulse is changed into a very -rapid one, due to vag-al palsy. Ex periments prove that the cause of the anxsthesia produced by this gas is due to asphyxia; for, if enough oxygen be in haled simultaneously to equal the pro portion of oxygen in ordinary aiY, anaes thesia does not appear. This addition of oxygen prevented the rise of arterial pressure usually produced by the gas, but did not interfere with the changes in the pulse-rate and force. For this reason it is believed that the action of the remedy upon sensation and the vaso motor system is separate from that upon the heart and its supplying nerves.
Under the administration of the gas the blood-corpuscles darken markedly, and the cyanosis is due to this and the diminution in the amount of oxygen present. There is no chemical conver
sion of the gas circulating in the blood. It enters the -body and leaves it as ni trous oxide. The oxyhmmoglobin spec trum of the blood is unaltered. It is not an asphyxiant, for narcosis occurs before the oxygen is exhausted. The heart's action is influenced but little, and pulsa tion continues for perhaps one minute. In complete narcosis there is a change in calibre of the renal vessels to corre spond with change in arterial pressure; renal secretion is rapidly lessened, and transitory albuminuria and glycosuria may occur (11IcCardie.) Therapeutics.—Nitrous oxide is prin cipally -used by dentists for the painless extraction of teeth. It is also used as an anTsthetie for minor surgical operations of short duration, for opening abscesses, boils, or felons; for tenotomies; and for i• I init. 1111T", diSIOCatiOn, ei C.
administered alone, mixed N. .L1* air or oxl,!._.2-,en, or alternately with When nsed pure, anzusthcsia is rt. qi kl v induced. For the weak, the d, or tile len- voung, it is best given with oxygen. Dare reports a case d ath after the inhalation of the gas "t as one of death due to the direct ,..ec of nitrons-oxide gas, but as an .,..-tance of the fact that the decided rise artt.rial pressure which is produced '•% the administration of this drug H• the period of amesthesia may cause tlie ruiture of a blood-vessel in persons '.r. ',aye a tendency to apople.xy. Yet ii,ortalit of this ant-esthetic is prac . all v ni/. In the l'nited States, where , used extensively, the mortality, ac -:.linz to 11IeC'arclie; has been less than it. one million administrations.
In producing narcosis a semirecumbent -ture should be avoided; the patient sit upright, with his head sup -n.11 on a rest connected with the ehair. In a ,eries of two hundred and fifty • ns.cutive eases results following acl •••inistration of nitrous-oxide gas: by the • n n ethod have been uniformly sue --ltd. It is erroneously stated that th• -doission of air interfere.s with the creet of the ,,as.