—This agent, composed of ethyl bromide 5 parts methyl chloride 35 parts, and ethyl chloride 60 parts, was introduced by Rowland, of Bordeaux, as a convenient means of producing an analgesic condition, i. e., something between complete anesthesia and conscious sensibility. The dose is about 5 Cc., to be sprayed upon a tightly fitting mask. The patient should be told to breathe and swallow as naturally as possible, and the effect is obtained within a few seconds. The agent is so speedy in producing its effects that it is sometimes difficult to tell when the proper degree of unconsciousness has been secured. A patient may be directed to hold up an arm in order that when it drops the surgeon may proceed. There is neither cyanosis nor corneal reflex, and nausea does not usually occur. The essential point of administration is the exclusion of air. Twenty seconds of administration will give from one to two minutes of anesthetic effect, during which various brief operations can be performed. By proper management this period can be lengthened many times.
Petroleum Ether.
—Petroleum ether was introduced by Schleich for the purpose of diluting chloroform. By itself it has a weak anesthetic power, and seems to possess some dangers of its own in the way of depressing the heart’s action and producing convulsions.
OTHER VOLATILE ANESTHETICS.
Schleich was among the first to demonstrate that the retention of an anesthetic within the body depends upon its boiling point. W. Meyer carried Schleich’s views still farther and showed the at least theoretical value of an anesthetic mixture whose boiling point was that of the normal blood temperature. If the evaporating point be much higher than the blood it is volatilized too easily, while if it be lower it reduces body temperature as it evaporates. After considerable experimentation Meyer recommended a mixture by volume of chloroform 3 parts, ether 2 parts, and ethyl chloride 1 part, and introduced this mixture under the name of anesthol. This composition does not seem to have met with great favor as yet, although it has theoretically much to commend it, as it seems slower in action and but little more satisfactory in other respects.
NITROUS OXIDE GAS.
This is by all means the most rapid general anesthetic in use. Patients can be placed under its influence in from twenty-five to sixty seconds. For a long time its employment was confined to dental practice, but it is now in general use by surgeons, as a preliminary to the use of ether or as the sole anesthetic agent. When managed properly patients can be kept for a half-hour or even an hour under its influence. Two disadvantages attend its administration: (1) It is difficult to completely relax the muscles and so maintain them that no difficulties are placed in the operator’s way, e. g., in certain operations upon the abdomen where muscle rigidity delays and makes difficult the operation. (2) The use of nitrous oxide alone so far impairs proper oxygenation of the blood that this fluid becomes dark or almost black and frequently obscures the field of operation. These difficulties, especially the latter, can be overcome by the skilful simultaneous use of oxygen gas, by which the blood is kept well oxygenated, and by which the deep stupor of nitrous oxide poisoning can be made so safe that it can be prolonged to the degree necessary to afford relaxation.
Nitrous oxide anesthesia is thus proved to be something more than mere asphyxia, or it would be completely counteracted by oxygen. Suitable apparatus can now be procured by which both gases can be blended together as desired; considerable experience, however, is necessary for their successful use. It is generally stated that nitrous oxide alone should not be given to persons with fatty hearts or atheromatous vessels. From a brief period of nitrous oxide anesthesia patients usually recover within a few minutes and without after-effects; still, relaxation of the sphincters may occur. After its prolonged use there may be considerable headache and vertigo.
THE CHOICE OF AN ANESTHETIC.
This will depend upon who is to be the anesthetizer as well as upon the actual condition of the patient. If an inexperienced person is to administer the anesthetic, ether is safer than chloroform, though slower. On the other hand, when given by an expert, and after due preparation of the patient, chloroform is ordinarily preferable. The latter is especially indicated in the young and aged, as well as in those who have bronchitis or chronic cough, and those who have advanced renal diseases or atheroma, because it is not likely to produce such high arterial tension.