Nitrous Oxide

Laughing-gas

Protoxide of Nitrogen

Protoxide of nitrogen. Laughing-gas.

Composition and Properties

A colorless, inodorous gas, having a slightly sweetish taste, and a specific gravity of 1·527. It consists of one equivalent each of nitrogen and oxygen. It increases the rate of combustion of inflammable substances. Water at ordinary temperature absorbs about three fourths of its bulk of the gas. By pressure and cold the gas may be condensed into a liquid, and can then be stored up in suitable vessels for transportation and use. The quantity of the gas taken up by cold water may be much increased by pressure, and the water will then yield it up on heating. Hence this constitutes a convenient mode of storing the gas for preservation. The ordinary mode of storing the gas is in gas-bags holding about eight gallons, in gasometers, or in the liquid form in strong metallic casks.

Physiological Actions

The first surgical operation performed with a modern anaesthetic was the extraction of a tooth, the subject being unconscious from the inhalation of nitrous oxide. It had long been known that this gas produced decided exhilaration when inhaled to a certain point. It has a very short anaesthetic stage, unless the inhalation of the gas be continued.

The first effect of the inhalation of nitrous oxide is a subjective dizziness, whirring noises in the ears, and tingling and loss of sensation throughout the body. Extraordinary illusions beguile the senses, and the intoxicated subject suddenly breaks forth into singing, declamation, sobbing, melancholy, or manifests a pugnacious tendency and assaults those about him. As the effects quickly cease, and as the return to consciousness is very abrupt, the subject is surprised and ashamed to find himself in some ridiculous or grandiose position quite foreign to his usual demeanor.

When used to produce anaesthesia for surgical operations, the inhalation of the gas is forced, and the stage of excitement is very brief. The countenance assumes a frightful aspect, most alarming to those who have not witnessed the inhalation of the gas. The face becomes deadly pale, the respirations, at first shallow, soon assume a stertorous character, the jaw becomes fixed, the eyes protrude, and the pallor of the face is presently replaced by a bluish and purplish tint.

So far as the exterior phenomena can afford any indication of the nature of the action, the condition produced by nitrous oxide is an asphyxiated state. The blood ceases to be oxygenated, carbonic acid accumulates, and the centers of conscious impressions are rendered inactive in consequence of the deficient supply of oxygen and the excess of carbonic acid. The rational indications of the nature of the narcosis produced by nitrous oxide are confirmed by physiological experiment. It has been found that the exhalation of carbonic acid is decidedly diminished by the inhalation of nitrous oxide, and that animals live no longer in an atmosphere of this gas than in an atmosphere of nitrogen.

The inhalation of nitrous oxide appears to be almost free from danger, and it is rare that unpleasant after-effects follow its administration. Four fatal cases have certainly occurred, which can with propriety be attributed to the lethal action of this gas, and various cases have fallen under the observation of the author in which nervousness, vague mental symptoms, and headache, have been experienced after the inhalations.

Therapy

The very prompt action of nitrous oxide and the quick subsidence of the narcosis render it a very useful anaesthetic agent when small operations, quickly executed, are to be performed. It is especially adapted for the extraction of teeth, opening of abscesses, and similar minor operations. But it has also been used successfully for maintaining prolonged anaesthesia for the performance of capital operations. There is no difficulty in keeping up insensibility from fifteen minutes to a half hour, since the introduction of liquefied gas and of apparatus for its suitable application.

It has been asserted that diabetes mellitus may be caused by its administration, but the evidence is far from satisfactory. That albuminuria may be induced thereby has also been alleged, but the evidence for this is still less conclusive. What danger soever arises in the course of its administration is due to the nature of its physiological actions, and can occur only in such subjects as have rigid arteries, or atheromatous degeneration, which may result from premature or actual old age. The blood pressure rises during the inhalation of the gas, and the venous stasis occurring, any vessel far advanced in the calcareous and fatty change may yield to the increased pressure and cerebral haemorrhage result. Some cases of apoplexy apparently thus induced have been reported. Ordinarily, should any threatening symptom arise during the administration of the gas, it is only necessary to withdraw the gas and apply artificial respiration.

Authorities referred to:

Amort, Dr. Robert. The Physiological Action of Nitrous Oxide. New York Medical Journal, August, 1870.

Johnson, Dr. George. A Lecture on the Physiology of Coma and Anaesthesia. Medical Times and Gazette, April 3, 1869.

Jolyet et T. Blanche, MM. Recherches expérimentales sur l'Action du Gaz protoxyde d'Azote. Bulletin Général de Thérap., vol. lxxxv, p. 91.

Richardson, Dr. B. W. Medical Times and Gazette, vol. i, 1868.