"On narcotism by the inhalation of vapours"

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By John Snow, M.D.

Vice-President of the Westminster Medical Society.

On the administration of chloroform-–Objections to giving it on a handkerchief--Description of an apparatus.

The conclusion generally arrived at by those who have commented on the fatal cases of inhalation of chloroform, is one in which I do not agree. It has usually been concluded that there is danger necessarily attending the use of chloroform, and that it should therefore be confined to serious operations. Now a great part of the advantage attending the use of an anæsthetic consists in its preventing the patient's dread of the operation; but if the immunity from pain could only be obtained by incurring a danger of sudden loss of life, there would be a new source of fear. Many patients, again, have been readily induced to submit to a necessary operation, through the prospect of undergoing it without pain, who, otherwise, would have withheld their consent either altogether or till the prospect of a successful issue were much diminished. In this way, there is no doubt, many lives have been saved. But if the patient had to choose between pain and a risk, however small, of sudden death, this ready and early consent could not be expected. It is therefore necessary, for the sake of patients undergoing capital operations, to inquire whether there is any means of preventing the pain, which is free from danger, and to employ that means in preference to another. And if the skilful [sic] and careful administration of chloroform were really attended with danger, I would recommend that it should not be resorted to in any case; for we have in ether a medicine capable of affording all the benefits that can be derived from chloroform, and which never caused accidents of the kind we are [840/841] considering, although it was the first used,--when the knowledge, consequently, of producing insensibility was less.* (*I am aware that ether was thought by some to have caused death in two or three instances in which the patients did not recover from the operation, but died two or three days afterwards; and in one of these instances a coroner's jury returned a verdict to that effect; but I believe the only instance on record in which the inhalation of ether was fatal, was one that occurred in France (see Gaz. Médicale, 4 Mars, and Med. Gaz. p. 432, last vol.), and in that case the inhalation was continued without intermission for ten minutes, although alarming symptoms were present nearly all the time; and it is probable that the result was owing as much to some defect in the inhaler, which limited the supply of air, as to the effect of ether.)

There is, however, no reason to doubt that chloroform is, when administered with care and a sufficient knowledge of its properties, unattended with danger,--or, at all events, with a degree of danger so small that it cannot be estimated;--not greater, for instance, than attends the minor operations of surgery, or the taking of ordinary doses of medicine. When the vapour of chloroform is well diluted with air, it is as safe as ether; and as it possesses some minor advantages over it,--such as being less pungent, and therefore more easily inhaled,--not leaving its odour in the breath for some time afterwards,--being more portable, on account of the smaller quantity required, and producing excitement less frequently in the early stages of its effects,--its use, by all medical men who are perfectly conversant with its effects and mode of administration, is quite allowable in every case in which there is much pain to be prevented.

But, without proper precautions, the inhalation of chloroform is undoubtedly attended with danger, on account of the rapidity of its action when not sufficiently diluted with air, and, also, on account of its effects accumulating for about twenty seconds after it is discontinued, which accumulation would be most formidable, if the air taken into the lungs just before, were highly charged with vapour. The exhibition of ether is not attended with this kind of danger, even if but little precaution is exercised, and the symptoms caused by both vapours being the same, I entirely agree in the recommendation of M. Valleix, physician to the Hôtel Dieu, that medical men who have not practiced anæsthesia should first study it from the action of ether.* (*See Med. Gaz. p. 305, present vol.) This advice will, perhaps, not generally be followed; but if practitioners are inclined to run any risk in administering chloroform before they are well prepared, they must recollect that they not doing it for the sake of preventing the severe pain and shock of the operation, but only to avoid the stronger odour, more pungent flavour, and other little inconveniences of ether.

It is quite obvious, that by merely placing the chloroform on a handkerchief or sponge, and getting the patient to breathe through it, we can have no control over the quantity of vapour in the air breathed. If the handkerchief be not applied close to the face, enough vapour will, most likely, not be taken to cause insensibility; and, if applied closely, the air breathed will probably be almost saturated, and that at a rather high temperature. In three out of the four fatal cases we have considered, the chloroform was administered on a handkerchief; and in the fourth case-–that in America-–no attention was paid to the proportions of vapour and air: the only endeavour appeared to be to make the patient insensible as quickly as possible. The handkerchief is advocated by some practitioners, on account of its supposed simplicity; but whenever I have had occasion to give chloroform in this way, I have felt it to be a very complicated process, on account of the difficulty of getting even an approximative knowledge of what I was doing, by the best calculation I could make.

Before administering chloroform, the surgeon should have as clear and distinct an idea of its vapour as of the blade of his knife; and as this will be read by students as well as practitioners, I shall be excused for introducing a brief explanation of the nature of a vapour. In a popular sense, this term is sometimes applied to the minute globules of liquid suspended in air, which result from the condensation of a vapour that has been mixed with it, as in what is called the steam or vapour from the spout of a tea-[841/842]kettle. But chloroform cannot be taken in this form; if it were attempted, spasm of the glottis would ensue. A vapour is a dry aeriform condition of a substance differing from a gas only in the circumstances of temperature and pressure under which it takes the liquid to form. The vapour of chloroform has no separate existence under natural circumstances of pressure and temperature, or in any form of inhaler. No patient ever took any of it in this way, or ever will, and this is equally true of ether.*

(*Many practitioners, judging from their writings, seem to have very incorrect notions concerning these vapours. For instance, M. Boux, the eminent French surgeon, in objecting to the use of the handkerchief in the Academy of Sciences, says-–"In this manner the patient inspires the chloroform vapour without air." (See Med. Gaz. present vol. p. 214). Soon after the inhalation of ether was introduced, two veterinary surgeons in London endeavoured to try its effects on a horse in a pure state, and prevented the ingress of air. As they did not make the ether boil, the animal could get not vapour, except what combined with the little air that might get in through the leakage of the inhaler. The horse in fact was burked. The efforts at respiration were prodigious,--it shortly died,--and the heart and diaphragm were found to be ruptured. (See Lancet, April 10, 1847). This experiment has been recently quoted in a pamphlet opposed to chloroform in midwifery, as proof of the injurious effects of ether.)

Chloroform requires a temperature of 140° Fah., under the ordinary pressure of the atmosphere, to make it boil, and enable it to exist in the state of undiluted vapour; but mixed with air, it may have the form of vapour at inferior temperatures: the quantity that may exist in the air varying with the temperature directly as the elastic force of the vapour. The chloroform, in fact, that a patient breathes, is dissolved in the air, just as water is always dissolved in it, even in the driest weather, and the patient breathes his air with two vapours instead of one-–the new vapour being, to be sure, in much the largest quantity. As a proof that these physical considerations are worthy our notice, I may state, that if chloroform had boiled at 180° instead of 140°, its solubility and other properties remaining the same, the four fatal cases we had occasion to discuss would not have occurred.

The following table shews the result of experiments I made to determine the quantity of vapour of chloroform that 100 cubic inches of air will take up at various temperatures:--

Temperature		Cubic Inches
50°	........	9
55°	........	11
60°	........	14
65°	........	19
70°	........	24
75°	........	29
80°	........	36
85°	........	44
90°	........	55

The most perfect way of giving a vapour to animals is that adopted in the experiments I have related, the breathing not being interfered with, and the strength of the vapour being accurately known. This method is not applicable to patients, but our endeavour should be to approach to it as nearly as we conveniently can. The apparatus I employ is delineated in the subjoined engraving.* (*It is made according to my directions, by Mr. Matthews, 10 Portugal Street Lincoln's Inn Fields.)

a. Outer case containing water bath, screwed on--b. Cylindrical vessel into which the chloroform is put; it is lined with a coil or two of bibulous paper up to the point c d. A cylindrical frame which screws into b-–it has apertures at the top for the admission of air, and its lower two-thirds are covered with a coil or two of bibulous paper, which touches the bottom of the vessel b, except where the notches e are cut in it. f. Elastic tube. g. Expiratory valve of face piece; the dotted lines indicate the position of this valve when turned aside for the admission of air not charged with vapour. h. Inside view of face-piece, pinched together at the top to adapt it to a smaller face. i. Inspiratory valve.

When the patient inspires, the air enters by the numerous and large apertures in the top of the inhaler, passes between the two cylinders of bibulous paper, wet with chloroform, through the notches in the bottom of the inner one, then up the centre of the apparatus, still in contact with the paper, and through the short tube, which is three-quarters of an inch wide in the inside. The air thus gets charged with vapour, whilst it meets with no obstruction whatever till it arrives at the inspiratory valve of vulcanized India-rubber, which weighs but a few grains, and rises at the beginning of the slightest possible inspi-[842/843]ratory movement. The cylinder of thin brass in which the chloroform is placed is inclosed [sic] in a larger one containing water, which, by supplying the caloric that is removed in the vaporization of the medicine, prevents the temperature from being lowered. It also prevents it from being raised by the warmth of the hand, and thus keeps the process steady. If the temperature of the water be 60°, each 100 cubic inches of air passing through the apparatus might, according to the table above, take up 14 cubic inches, and become expanded to 114 cubic inches, when it would contain a little more than twelve per cent by measure. This is supposing it became quite saturated, which, however, it does not, and ten per cent of vapour, or eight minims of chloroform, is probably as much as the air contains. It is not desirable, however, to give it to the patient even of this strength, and the [843/844] expiratory valve of the face-piece* is made to move to one side, so as to leave uncovered more or less of the aperture over which it is placed, and admit pure air to mix with and dilute that which has passed through the inhaler. By means of this valve, the vapour may be diluted to any extent, whilst, at the same time, one may have a knowledge of the strength of the vapour the patient is breathing; not exact, to be sure, but practically of great value. The valves in this face-piece act properly, and close of themselves, in every position in which a patient can be placed, except on his face, and even in this posture they will act of the head be turned on one side. (*It is the same face-piece I used in giving ether for three or four months before Dr. Simpson introduced the use of chloroform. By the removal of the peculiar expiratory valve, which is its most important part, and the introduction of a sponge, it has been made to constitute a chloroform inhaler by more than one practitioner. These inhalers are, undoubtedly, better than the sponge or handkerchief; but, besides the want of affording due command over the strength of the vapour, I consider that they are open to objection from the chloroform being so near to the mouth, that some of it might be inhaled, by a forcible inspiration, in the form of minute drops, when it would cause temporary spasm of the glottis.)

The position of the patient and inhaler have nothing to do with the specific gravity of the vapour, as some have supposed. If what the patient breathes were as heavy as the pure vapour, it would impose no appreciable labour on the muscles of respiration to raise it to the mouth; and although the vapour of chloroform is four times as heavy as atmospheric air, it does not increase the specific gravity of the air the patient inhales by more than one-fourth; and, indeed, air charged with vapour of chloroform is not so heavy as when charged with vapour of ether at the same temperature. The most convenient position of the patient taking chloroform is lying on the back or side, with the head and shoulders a little raised, as he is then duly supported in the state of insensibility, and can be more easily controlled if he shall struggle whilst becoming insensible. But there is no objection to the sitting posture, when that is most convenient to the operator.

In the next paper, I shall enter on the details necessary to be observed in giving chloroform in different kinds of surgical operations.