CHAPTER XI.
CHLOROFORM.
Physical Characteristics.
Chloroform is chemically trichlor-methane, CHCL3. It is a colourless, transparent fluid, with a specific gravity of 1·491 at 17°C. Its vapour is even heavier than that of ether, approximately four times heavier than air. It is not inflammable, but the action of an open fire or naked flame tends to break it up into hydrochloric acid and phosgene, both of which are highly irritant gases to all who breathe them. The patient suffers, but since all the other occupants of the theatre are also affected, warning is given before serious harm has been inflicted.
Chemically pure chloroform is a somewhat unstable product, but the addition invariably made to it by the producers, of a trace of alcohol, prevents any serious risk of decomposition in bulk. It should be neutral in reaction and have an agreeable non-irritating odour: departure from the normal in either respect indicates the possibility of the presence of acids or aldehydes, and the necessity for referring a specimen to the laboratory.
Like ether, chloroform may be obtained from pure ethyl alcohol or from methylated spirits, and the remarks made in the chapter upon ether apply to the case of chloroform also. A third source of supply is acetone, from which perfectly good chloroform can be produced.
Physiology.
Chloroform is an irritant to the skin and mucous membranes. A drop left on the skin and covered over with impermeable material will produce a deep and painful blister. A drop falling into the eye, if not instantly washed away, produces a very powerful inflammatory reaction, and many eyes have been totally lost from carelessness in this respect. Such incidents are of course actionable, and heavy damages may be given.
Fig. 35.—Diagrammatic representation of various blood pressure curves obtainable with chloroform.
Line ABA′ represents curve desired in normal chloroform administration.
Line ABCB′ represents gradual overdosage.
Line ABCC′ represents recovery by inversion.
DD′ represents syncope from vagal inhibition: in its course, one attempt of the heart to “escape” is shown.
The special peculiarities of the action of chloroform upon the nervous system have already been emphasised in the account given of the physiology of ether (see page 75). Its action upon the circulatory and respiratory systems has been the subject of many researches, and of much embittered controversy. The literature is therefore very extensive, and the account of it must be severely condensed. The following may be taken as a brief resumé of present day opinion (see Fig. 35):—
(1) In every case of chloroform administration, there is a fall of blood pressure.
(2) If the drug be presented in weak concentration (less than 2 per cent. vapour strength), the fall is gradual and even (line AB).
(3) If the same strength (say 2 per cent.) of vapour as produced the above effect be prolonged unduly, the respiration will cease at a time when blood pressure is still well above zero (line ABCB′).
(4) The fall of pressure is due to diminished force of cardiac action, and at a later stage also to vaso-motor paresis.
(5) The cessation of respiration is due partly to fall of blood pressure in the vessels supplying the medullary centre; partly to gradual poisoning of the centre itself by the drug. That the fall of B.P. in the cerebral vessels is in itself one explanation of the cessation of respiration, was proved many years ago by Leonard Hill in his inversion experiments. Just at the stage when respiration had ceased, the anæsthetic was withdrawn, and the animal inverted into the head-down position. The B.P. in the carotid at once began to rise, and natural respiration was resumed (line A′BCC′).
The above conclusions refer to chloroform given in moderate vapour strength; other effects are produced if higher percentages are administered:—
(6) With high concentration of chloroform vapour, the fall of blood pressure is rapid, and is apt to become suddenly precipitous (line DD′).
(7) The cause of these sudden falls is inhibition of the heart by over-activity of the vagus: cutting the vagi always terminates the effect unless delayed so long that the animal is dead: in an animal fully under atropine, these vagal actions cannot be produced.
(8) If the heart is inhibited by vagal action, the respiration ceases at once, usually after one deep inspiratory sigh.
(9) An inhibited heart may “escape” from vagal action before the animal is dead: frequently, however, the inhibition persists and the animal dies.
(10) Struggling and breath-holding in the early stages of induction cause sudden falls of blood pressure. Many observers believe that these falls also are due to vagal activity, others hotly deny this. All are united in believing that to press chloroform upon a patient who is struggling and holding the breath, is fraught with grave risk of causing sudden syncope.
(11) The abnormal irritability of the vagus above referred to is a feature mainly of the induction stage, disappearing once full anæsthesia is developed.
(12) It is an undoubted clinical fact that there is a risk of sudden arrest of heart’s action if the operation is begun before the stage of full anæsthesia is reached. A reasonable explanation of such accidents is furnished by supposing a reflex inhibition acting through the vagal centre already rendered hyper-sensitive by partial chloroformisation.
Views of Goodman Levy.
This worker has demonstrated in animals that the heart is sometimes thrown by chloroform into the condition of fibrillation—a delirium of the cardiac muscle, from which recovery is rare. It occurs in the early stage, before full anæsthesia has been reached, and is predisposed to by the infliction of trauma. The practical outcome of this is that the induction stage of chloroform should not be unduly prolonged, and that the operation should not be begun until the third stage is fully developed.
So far as the author understands the views of Dr Levy, his explanation of chloroform syncope need not be taken as introducing any new principle into the administration of the drug. Even those who lay most emphasis upon the danger of using vapours of too high a percentage strength would admit the force of Levy’s contentions. As usual, safety lies in steering between two extremes.
During his work on this subject, Levy further demonstrated that the introduction into the circulation of adrenalin during incomplete chloroform anæsthesia was very liable to induce fatal cardiac fibrillation. He thus furnished the explanation of a number of deaths which had occurred in the practice of nose and throat specialists. Since the publication of Levy’s work, the rule has been absolute that if adrenalin is to be used in a case requiring chloroform anæsthesia, the adrenalin must precede, not follow the anæsthetic.
Administration.
Basing upon these views as to the action of chloroform, and upon the lessons of practical experience, we may formulate definite rules for giving the drug.
General Principles for giving Chloroform.
(1) Give chloroform evenly, not spasmodically.
(2) Increase the vapour strength of chloroform gradually from zero until 2 per cent. or at most 2½ per cent. is reached at the end of two or three minutes; maintain that strength until full anæsthesia is obtained; thereafter, drop down to 1–1·5 per cent. This will result in a B.P. curve corresponding to the line ABA′ in the diagram (Fig. 35).
(3) Be guided chiefly by the patient’s respiration. Chloroform kills by stopping the heart, but in the immense preponderance of cases, evidence of failure of respiration appears in ample time to give warning of approaching circulatory failure. The eye reflexes give confirmatory evidence of the depth of anæsthesia, but the superlatively important thing is to maintain a free airway, and be sure the patient is using it.
(4) If serious struggling and breath-holding occur, withdraw the anæsthetic until the patient “resumes normal.”
Methods of Administration.
The logical application of such general principles would be to use an instrument which gives a definite and known percentage of chloroform, variable at the wish of the administrator. Many such machines have been brought forward, and while none of them have obtained general acceptance, a description of the best known instrument will be given, as the reader may as a house-surgeon meet with it, and with a surgeon who wishes it to be used.
Vernon Harcourt’s Inhaler.
In principle, this is a “draw-over” instrument; the patient’s own inspirations are the motive power. Passing over the surface of the fluid drug, the inspired air picks up from it a known percentage of vapour. The other system available for the construction of percentage chloroform instruments is the “plenum”; in this the vapour is propelled to the patient by a pump.
Fig. 36.—Vernon Harcourt’s Percentage Chloroform Inhaler.
In appearance, the inhaler resembles the letter T, with a rubber face-piece attached to the lower end of the vertical limb (see Fig. 36). The T portion itself is made of metal tubing of a definite size in cross section. One end of the horizontal limb admits pure air, the other, air which has passed over chloroform and picked up from it a certain proportion of vapour. The proportion of the total inspired volume of air which passes through each of the ends is regulated by a lever seen at the junction of horizontal and vertical limbs, and the exact percentage of chloroform being inhaled is indicated by a series of numerals marked on the dial over which the lever moves. These figures are correct provided:—
(1) The chloroform receptacle is not shaken (this would greatly increase the percentage).
(2) The temperature of the chloroform is not allowed to fall below 13° centigrade. To ensure that this cannot take place without the knowledge of the administrator, two coloured beads are thrown into the chloroform. At the desired temperature of the chloroform (13°-15°C) the blue bead sinks to the bottom, the red one nearly to the bottom. Below 13°C, the red bead also touches bottom, and when this is observed, the chloroform vial is warmed up in the palm of the hand. At the point 15°C, both beads float, and the warming must then stop, or an undesirable addition to the vapour strength yielded will occur.
The face-piece is made of rubber, and must be closely adapted to the face; in its side is seen the expiratory valve. Inspiratory valves are present at each end of the horizontal limb.
The great advantage of this instrument, to the author’s mind, is for teaching or demonstration purposes. If the student sees the lever gradually being moved over from ·2 to 2 per cent., then slipped back to about 1·5 per cent. after full anæsthesia has been obtained, he begins to appreciate what it is he is aiming at when giving chloroform by the ordinary open method.
Fig. 37.—Schimmelbushch’s mask.
Open Method.
The appliances requisite are:—
(1) A mask. Schimmelbushch’s is the best known (Fig. 37): as elsewhere explained, it does not accurately fit the face.
(2) Material to stretch on the mask. The best is two layers of domette or one of flannelette: surgical gauze is so light that heavy drops of chloroform are apt to “spark” through it and burn the skin of the face: lint rapidly becomes sodden; the drug drips away from its edge instead of vapourising properly.
(3) A good drop bottle, of which many varieties are marketted (Fig. 38): it is essential that it should be capable of producing definite drops: the old method of intermittent “douching” of chloroform is to be condemned as violating the first general principle for giving the drug.
Fig. 38.—Chloroform drop bottles.
It is not possible by the open method to be mathematically accurate with percentages, but the necessary appliances are simple, easily transported, and practically always at hand. If the student learns to use it, and while doing so to think in percentages, he will achieve as good results as or better than he will with percentage instruments. While he may not have in front of his eyes a dial which shows the percentage graphically, observation of the patient will inform him whether the percentage being given should be maintained, raised, or lowered. The only remaining point for him to realise, then, is how in practice such regulations of percentage strength can be achieved by the open method. The strength of the vapour will depend upon three factors:—
(1) Nature of the material used on the mask.
(2) Closeness with which the mask is adapted to the face.
(3) Amount of chloroform exhibited on the mask.
To ensure uniformity of result, two of these factors should be kept constant, and the necessary increase or decrease of vapour strength achieved by varying the third. Always use the same type and thickness of material on the mask, and allow the mask to lie lightly on the face. If the amount of chloroform is then regulated by a strictly “drop” method, results of great uniformity may be obtained by the open method.
The Junker Inhaler.
This instrument was originally introduced as an attempt to achieve a percentage method. Air is pumped through a certain depth of chloroform contained in a bottle, and the vapour brought to the patient in the face-piece shown in Fig. 39. The calculations by which it was sought to establish this as a reliable dosimetric or percentage method are of no great value. From that standpoint the instrument has not achieved success. It delivers to the patient a small quantity of high percentage vapour which is diluted by a much larger quantity of air inspired by the patient from the general atmosphere, and the final percentage inhaled by the patient is therefore no more accurately known to the administrator than in the open method.
The instrument is, however, of considerable value for tongue and jaw cases, where anæsthesia has to be maintained for some considerable time after the mask with which anæsthesia has been induced has had to be removed, to give access to the surgeon.
Fig. 39.—Junker’s Chloroform Inhaler showing hand bellows, bottle and mask. Alternatively to the latter, the nasal tube shown above, may be used.
The Figure 39 shows the instrument as usually marketed. It consists of:—
(1) A hand-bellows.
(2) Chloroform bottle. A mark cut on this shows the level to which it is to be filled: if more than the proper quantity be poured in, droplets of fluid chloroform are apt to be blown along the exit tube, with dangerous results.
For convenience and neatness, it is usual to make the exit surround the inlet tube. The entering air bubbles through the chloroform, and a stream of air and chloroform vapour passes out from the exit tube.[10] It is unnecessary to give a detailed account of the use of the instrument, but the student must remember the following points:—
(1) The amount of chloroform vapourised will depend on the vigour of the pumping, the depth of fluid, and the temperature of the chloroform. In order to achieve uniform results, it is therefore necessary to keep up a steady but not excessive pumping, to warm up the bottle occasionally by holding it in the palm of a disengaged hand, and to watch that the level of the chloroform does not fall too low.
(2) The pumping should be timed to synchronise with inspiration: a puff of vapour delivered during an expiration will be wasted.
Advantages and Disadvantages of Chloroform.
The light portable appliances which are alone necessary for chloroform anæsthesia, the comparative cheapness of the method, and the apparent ease with which its administration may be conducted, are all great temptations to its use. Those who feel the temptation strong upon them are advised to remember the following quotation from the writings of Professor Leonard Hill:—
“Chloroform is a drug used by the young anæsthetist with the utmost hardihood, and until he has had the misfortune in his practice to meet with a death caused by it, he derides the danger of the drug, and asserts that its safety merely depends on the care and skill of the administrator. After losing his patient, he falls to descanting on the unavoidable dangers of the drug, dangers which he is now the first to maintain cannot be met by any degree of skill in administration.”
The most distressing and probably the most common chloroform fatalities are exemplified in administration given for the most trifling conditions, such as opening abscesses or extracting teeth.
In general, we use chloroform if for any reason ether is not applicable. For examples of cases of this description, the reader is referred to the chapter upon the choice of anæsthetics.