Handbook of anæsthetics

The drug commonly known as ether and otherwise described as ethylic ether or sulphuric ether, has a chemical formula (C₂H₅)₂O. It is a transparent colourless fluid with a specific gravity of ·720 to ·723. A brand much used in the States has an S.G. of ·713 only, a point which is greatly emphasised by its supporters, who claim that it volatises quicker and therefore is more powerful in action. The author has in actual practise not found much difference between this brand and any good British one.

Ether is highly inflammable and volatilises readily at ordinary room temperatures. Its boiling point is 96° to 98° Fahr. Whether evaporating from a fabric such as gauze, or from bulk in a jar, ether cools very rapidly, and the fall in temperature soon reduces the ease of its volatisation. This point is of some practical importance in anæsthetics, and some years ago the author made a number of observations, hitherto unpublished, with a view of ascertaining some definite facts in this connection. His results will be found in Appendix I.

Ether vapour is heavy—two and a half times heavier than air. It therefore tends in a room to flow towards the floor, and to remain for some time unmixed with the general atmosphere. Since it is highly explosive, this constitutes a definite danger if any naked light or open fire is present. Everyone who handles ether should bear in mind these physical peculiarities of its vapour.

Ether is affected by prolonged exposure to bright sunlight, and also by prolonged bubbling through it of air, nitrous oxide, or oxygen. Ether which has been subjected to any of these measures should be inspected before being put back into reserve, and if any brown discoloration is noticed, it should either be sent to the hospital laboratory for redistillation, or presented to the theatre sister for use as a cleaning agent. Such contributions are always gratefully received.

Most of the ordinary impurities of ether are acid in reaction, while ether itself is absolutely neutral. Any specimen which turns litmus paper red should be sent to the laboratory for examination.

Sources of Supply.

Ethylic alcohol may be prepared either from ethyl alcohol or from methylated spirits. In the former case it carries, however, the cost of the duty imposed upon potable spirit, and since perfectly good anæsthetic ether can be prepared from the latter source, it is waste of money to use the more expensive article.

Physiology.

Ether acts upon the nervous system like other anæsthetics: as compared with chloroform, however, the stage of excitation of each centre before its paralysis is apt to be marked. There is, therefore, in some subjects, a greater tendency to struggle; healthy subjects properly handled do not show much evidence of irritation of the cerebrum. All, however, show some evidence of stimulation of the respiratory centre, which is not prolonged. Prolonged deep and rapid respiration under ether is due to other causes than the action of the drug itself. It is of course seen in “closed ether,” but the active agent is excess of CO₂, not ether.

The working margin of safety in ether, i.e. the stage between loss of spinal reflexes and the poisoning of respiratory centre is much wider than in chloroform.

Some experiments of Waller made many years ago showed that upon nerve tissue, ether acts much less powerfully than chloroform: in the proportion, he found, of one to seven or eight. These laboratory results have received entire confirmation by later workers who have estimated the actual vapour strength required of either drug to produce or maintain anæsthesia. Roughly, to induce anæsthesia, we require 2 per cent. chloroform, or 16 to 18 per cent. of ether (see Appendix II.).

The Circulation.

The first effect of ether is a temporary stimulation of the heart, which beats more rapidly and more strongly, thus raising the blood pressure. This effect is not very prolonged; like all other drug stimulation, it is followed by depression. In the healthy subject properly anæsthetised, such depression is very moderate in degree, and in a normal administration it is probable that the heart, after the first few minutes, is acting very much at its normal speed and force. Ether is, however, a marked vaso-dilator, and the net result upon blood pressure is a slight fall after the first few minutes.

If the method in use is “closed,” the pressure remains slightly raised for some considerable time, usually throughout the administration. The slight anoxaemia induces a vaso-constriction; and the CO₂ excess, in the view of Henderson (see page 10), maintains a good return of venous blood to the heart and a satisfactory cardiac output. For a note of certain blood changes resulting from ether and other anæsthetics (see Appendix III.).

Respiratory System.

In addition to the effect upon the medullary centre already referred to, ether effects the respiratory tract more profoundly than other anæsthetics. The mucous membranes are irritated, and in some cases there is a great outpouring of mucous. Though usually limited to the upper part of the tract (nose, pharynx, and trachea), the irritation sometimes extends deeply into the chest, affecting even the small bronchioles. These unpleasant effects of ether are in the great majority of cases, quite transient: after the first ten minutes no addition to the secretions is noticed. In a minority, however, the effect persists, the whole chest is filled with moist sounds, and persistence with the drug is impossible.

The kidneys are always slightly irritated by ether, and if they are or recently have been subject to inflammatory disease, a very acute exacerbation is apt to follow the use of the drug. In the healthy kidney this is not to be feared, nor does it seem to be an appreciable danger where one kidney is sound, even if the other is the seat of gross organic disease necessitating its drainage or removal.

Methods of Administration.

Many methods have been tried, but those which at present hold the field are—

(1) Closed Ether.

The two inhalers originally brought out for this were Clover’s in London, and Ormsby’s in Dublin. At a later date Hewitt’s “wide bore” modification of the Clover was introduced.

(a) The Clover instrument (see Fig. 23)[4] consists of a face-piece, a dome-shaped ether chamber, and a one-gallon bag, usually attached to the top of the ether chamber by a T-shaped tube. The details of the method by which the amount of ether inhaled by the patient is graduated are best appreciated by unscrewing the milled head at the top of the dome, and withdrawing the tube which runs through it (see Fig. 24). In the tube will be found two slots, one about half an inch above the other, and each extending for half the circumference of the tube. Between these two slots the tube is divided by a diaphragm. In any case, therefore, air passing up or down the tube must pass in and out of these slots.

Now turn to the tubular space left in the dome piece, and examine visually and with the finger its interior. On the one side of its middle will be found two slots leading into the circular ether chamber which occupies a large part of the dome. On the other side will be found a small cavity, as deep from above downwards as the two slots combined, but not communicating with the ether chamber. It is obvious that with the tube inside, if this cavity is opposite the slots in the tube, air will pass up the tube out of one slot and back into the other, without coming into contact with the ether at all. If on the other hand the slots in the tube are opposite the slots in the ether chamber, the air passes over the surface of the contained ether, and volatises some of it.

Intermediate positions of the tube give a condition where part only of the air passes over the ether. The indicator attached to the tube, combined with the figuring “O, one, two, three, full,” to be found on the outside of the base of the dome, shows at any moment what proportion of the air is passing into the ether chamber.

To use the instrument, fill the metal measure provided with ether, withdraw the stopper from the ether chamber, and pour in the ounce and a half of ether which the measure contains. Replace the stopper, and blow through the tube to expel any ether vapour which may have appeared in it. Leave the rubber bag at first unattached: the patient will feel more comfortable if during the first minute the top of the tube is open. With the indicator at 0 adapt the face-piece to the face and allow the patient to breathe up and down the tube. By rotating the dome, ether is then gradually turned on, until the figure two is reached in the first minute. The indicator is then slipped back nearly to zero for a second, and the rubber bag slipped on during an expiration: it must be moderately inflated to supply the requisite volume of air for respiration.

The rotation of the dome is again begun and the indicator is made to travel away from the zero, until at the end of about five minutes, it reaches “full.” After the first few minutes, it will be necessary to give an occasional breath of fresh air, otherwise an undesirable degree of cyanosis will result, but it must be done with great discretion, or struggling will ensue. At the end of about five minutes, anæsthesia should be fully established. A little extra ether is then poured into the chamber, the indicator pushed back to about “two” and the administration continued. One breath of fresh air is given in every three or four. Spells may be given with the bag off altogether, but during such periods the indicator will require to be advanced a little, and refills of ether provided more frequently than would be necessary if the bag were on.

Hewitt’s-wide-bore.

The principle of this is identical with that of the Clover, but the channels being wider, there is less mechanical interference with the ingress and egress of air. The actual construction differs also, in that to turn on the ether, instead of rotating the dome, one moves the indicator (see Fig. 25). The instrument certainly gives results a little better than those obtainable by the Clover, but it is heavier, and rather more bulky.

Ormsby’s Inhaler (See Fig. 26).

This consists of a facepiece, a cage made of wire or thin steel slips and containing a sponge; and lastly, a one gallon bag which fits over the cage. In the face-piece is an air vent, which can be either entirely closed, partially or entirely opened.

To use the instrument, take out the sponge and warm it either by wringing it out of hot water, or better by leaving it a few minutes on the top of a hot steriliser. Push it back into the cage, open the air vent fully, and holding the inhaler upside down, pour on to the sponge a measure full (about half an ounce) of ether. Tell the patient to inhale deeply, and then catch the resulting expiration in the bag by quickly adapting the facepiece to the face at the appropriate second.

After a few seconds, begin to close the air vent, when it will be found that the bag begins to wax and wane with each expiration and inspiration respectively. After the first three minutes, the inhaler must be removed, more ether poured in, the air vent opened again partially, and the inhaler again applied to the face. After full anæsthesia is induced, the air vent may constantly be left partially open.

N.B.—It must be observed that the air vent is not valved: it is merely an opening through which part of the respired air may pass in and out without going near the ether sponge.

In actual practice, the induction stage of closed ether is almost invariably assisted by using either nitrous oxide, or a small dose of ethyl chloride as a preliminary: these methods are described in Chapter XV.

The question now arises, what scope is to be assigned in modern anæsthesia, to closed-ether methods. Formerly a large proportion of anæsthesias, long or short, were conducted by the closed method, and while the greater number of anæsthetists no longer utilise them to the same extent as formerly, they may still be regarded as of the utmost value in a limited class of cases. They are speedy in action, powerful enough to overcome the most refractory patient, and with reasonable skill very safe. On the other hand, the anæsthesia obtained is not of the most desirable type. There is a great deal of salivation and mucous secretion from the respiratory mucous membranes; the respiratory movements are deeper than in open methods, from the excess of CO₂ present in the blood, and this leads to a good deal of heaving of the abdominal wall, which may be most troublesome to the surgeon if he is opening or closing that cavity. Moreover, after their use more headache, malaise, and vomiting occur than after open-ether, and perhaps a little more tendency to bronchitis or pneumonia. For these reasons, many anæsthetists and surgeons now object to their use in abdominal surgery, though some still adhere to them for the induction stage, passing to the open method when the patient is once well under.

(2) Open Ether.

As already explained the strictly accurate term for this is Perhalational Ether, but so cumbersome a terminology stands small chance of general acceptance.

Apparatus.

The essential points in a proper outfit have already been explained (see page 28) and are all well met by the mask and ether dropper introduced by Mr Bellamy Gardner (see Fig. 27). The mask is covered with from twelve to sixteen layers of gauze, and lies on the gauze ring, shown in the Fig. 28A, which completes the fit between face and facepiece. The dropper fits into the ordinary six ounce dispensary bottle: the long arm dips into the ether, the short one allows air to enter the bottle to replace the ether used. A dropper can also be improvised by using a cork with slots cut at each side and with a gauze or wool wick inserted along one of these. The author finds these uncertain in their action, however: with Gardner’s dropper, a steady flow of drops of ether slow or fast as required, can always be obtained once the student has acquired the knack of using the appliance.

To Mr Bellamy Gardner’s outfit, the author adds a folded towel, pinned at one corner, so as to form a short cone. The base of this cone embraces the mask and face; through its upper apperture the anæsthetic is dropped on to the mask. The cone can be rotated into the position most convenient for this purpose in any given position of the patient’s head (Fig. 28).

Problems of the Induction Period.

Open-ether is not a powerful anæsthetic, just not powerful enough for one to be sure that one can induce full anæsthesia with it alone, in a powerful subject. The reason for this is shown in Appendix II, and may be here condensed by explaining that some 18 per cent. to 20 per cent. of ether vapour is required to induce anæsthesia, while it is not easy to get more than 14 per cent. off an open mask. How is this situation to be met?

Reference has already been made to one solution of the problem. A closed ether method may be used for induction, and this practice is widely used. The author does not often adopt this course, fearing that the undesirable features of closed ether may persist even after the change to an open method has been made.

Another possibility even more widely favoured is to use chloroform as the inducing agent, and only to turn to ether when full anæsthesia is obtained. To this plan the author is strongly opposed. It exposes the patient to the risks of the induction stage of chloroform which are much greater than those of the later stages. Moreover, to develop the full advantages of open-ether, a preliminary hypodermic of morphia is essential, and the drawbacks of chloroform plus morphia are elsewhere mentioned (page 43).

The use of a mixture of chloroform two parts, ether three parts, presents the same disadvantage, but in a degree so much smaller that in powerful or alcoholic patients, the author believes this to be the method of choice (see Chapter xiv.).

Dr Silk has recently suggested another plan. He has sought to make open-ether easy for the non-expert with a view of encouraging the wider use of so valuable a method. For this purpose he advocates the admixture of one part of chloroform in thirty-two of ether (a dram of chloroform in four ounces of ether). This is to be given in exactly the same way as perhalational ether, and will, Silk says, give a type of anæsthesia, and a degree of safety, identical with those of pure ether. The author’s experience with Silk’s mixture is too limited to enable him to offer any opinion upon its merits.

Lastly, there remains the plan of using ether as the main inducing agent, but assisting its action by the intermittent and most guarded addition of small quantities of C₂E₃ mixture. This is the author’s “stock” method; but in teaching it to students, too much emphasis cannot be laid upon the small quantities of chloroform mixture required or permissible. As a consequence of the perhalational method here advocated, every drop of chloroform which appears on the mask will when volatilised, give a very much higher percentage of CHCL₃ vapour in the inspired air, than the same quantity exhibited on the ordinary open chloroform mask. Once the student has grasped this essential fact, ordinary care and intelligence will enable him to guard against a danger which is only existent if unappreciated.

The Administration.

For many of the hints given in this section the author is indebted to Dr W. J. Ferguson of New York, and Dr Hornabrook of Melbourne.

Success in inducing with open-ether is attained only by attention to a number of small details. The student who thinks that some of these are too trifling for his notice is usually the man who informs you that induction by open-ether is impossible, the fact really being that he has not taken the trouble to learn, or has never had proper tuition. The following are the points demanding attention:—

By the use of the method here advocated, induction is singularly easy and successful in good subjects. The struggling stage is either not represented at all, or appears only in the form of the lifting of a limb and a slight occasional pause or catch in respiration. Full anæsthesia is often announced audibly, by the commencement of a gentle “blowing.” Once it is heard, the anæsthetist may rest assured that a workable level of anæsthesia is either present or not far off.

Amounts of Ether required.

If the above instructions are followed, the amount of ether required is not excessive. Anæsthesia is attained after the use of about 1½ to 2 ounces of ether and one or two drams of mixture. The next forty to fifty minutes demand about another four or five ounces of ether; no mixture at all. Some practice, is required before these small figures are attained. The more practice, the less ether is required.

III.—Vapour Anæsthesia.

In a sense, all forms of ether anæsthesia are vapour methods, but in all the forms so far described, the patient has to vapourise the drug for himself: in a true vapour anæsthesia this is done for him, and the mixture of air and ether vapour propelled towards him. One of the keenest advocates of this method is Dr Gwathmey, of New York. He lays great stress also upon the necessity of warming the vapour, claiming that this measure will prevent the loss of heat to the patient incidental to the warming up in the air passages of the cold vapour usually supplied by other methods; but the results of the laboratory experiments upon which Gwathmey founded his case are inapplicable to the human subject, in that they were performed upon dogs and cats, which lose heat largely from the mouth and air stream. Man is not a hairy animal, and transacts most of his thermolysis through the medium of his skin. None the less, warming the vapour of ether has value since the process removes some of the irritant effects so marked in the case of cold ether vapour.

Apparatus for the Vapour Method.

In 1913, Karl Connell described such an apparatus, which was then in use at the Roosevelt Hospital, New York. The ether was vapourised by dropping it into a warm chamber. Air was pumped into the chamber, and carried the ether vapour in known percentage, and at known pressure as shown by gauges. Such mechanism is ideal, but would certainly be rather costly. Its great value was that it informed us with certainty what proportions of ether in the atmosphere were necessary to induce and maintain anæsthesia (see Appendix II.).

A simple mechanism was brought out shortly afterwards by Dr Shipway, of Guy’s, and is known as Shipway’s warmed Ether.

It consists essentially of the following parts (see Fig. 29):—

This little machine, somewhat resembling a cruet stand in its appearance was widely used in France. Owing to the kindness of the Edinburgh Red Cross Committee, one was provided for the Base Hospital with which the author proceeded to Salonika, where he used it extensively. The impression of it formed by himself and others was that it was peculiarly easy to maintain with it a steady level of anæsthesia. It had, however, no claim to banish post-anæsthetic bronchitis and pneumonia, of which in spite of much anxious care and thought, a fair number of cases were seen during the winter time (see page 151).

In using the machine, it is necessary to remember that from the physical point of view, one is providing from the machine a small part only of the total volume of air required by the patient.

The bellows are quite small: one squeeze of the hand will not supply more than about the equivalent in volume of one or two fluid ounces. The larger part of the volume required by the patient has to be obtained from the general atmosphere, so that the percentage of ether which may be as high as 25 in the exit tube, will be greatly lowered by the time it reaches the patient’s respiratory tract.

The actual strength of ether breathed by the patient will depend upon:—

With specimens of this machine which have the addition of the chloroform bottle, it is perfectly possible to conduct even the induction stage of anæsthesia; a mere trace of chloroform vapour will be sufficient. It is unnecessary to give detailed instructions for the use of the machine. A preliminary consideration of the above physical facts, together with a little cautious practice, will enable the student rapidly to acquire facility with the method.

IV.—Rectal Etherisation.

For such operations as the removal of jaw or tongue there are obvious advantages in being able to introduce ether vapour to the blood per rectum, since the mouth and air passages are thereby left free for the attention of the surgeon.

Many years ago this was attempted by vapourising ether and propelling the vapour through a tube high up into the rectum. This method was abandoned, as it led to a good deal of inflammatory trouble afterwards. Recently, Dr Gwathmey suggested a new method of utilising the rectal route which has largely overcome this objection.

Gwathmey’s Oil Ether Method.

This consists in passing into the rectum a mixture of olive oil and ether. The bowel is first carefully washed out, and an hour before operation, the patient receives a hypodermic of morphia, gr. ⅙; atropine, gr. ¹⁄₁₂₀. A suppository of chloretone gr. v is also passed into the rectum to act as a local sedative. Half-an-hour later, the patient is put into the left lateral position, a soft catheter attached to a funnel is passed some six inches up the rectum, and the mixture of oil and ether poured into the funnel. It is wise to take at least five minutes to introduce the whole dose.

The following table shows the dosage required:—

In practice then, for the ordinary adult, one uses eight ounces of the mixture, six ounces of which are pure ether. The oil and ether require to be shaken together, but remain blended long enough for introduction.

In five or ten minutes, the patient begins to feel a rather pleasing numbness and tingling in the lower, and later the upper extremities, and drops quietly to sleep in about twenty minutes. In a large proportion of cases, it is necessary to deepen the anæsthesia by the use of the open mask for a few minutes, but once a deep anæsthesia has been thus obtained, the absorption from the rectum will balance the loss in expiration and maintain a good anæsthesia for three quarters of an hour at least.

On return to bed of the patient, the nurse passes two tubes placed side by side, as high into the rectum as she can; the end of a Higginson syringe is inserted into one of them, and a considerable quantity of soap and water is pumped gently into the bowel, escaping down the second tube. The washing must be continued until all smell of ether is removed. Finally the soapy water itself is washed away by a little saline.

Unless there be some pre-existing local inflammatory disease of the rectum (in which case the method should not be used), there are no unpleasant sequelæ after oil ether. The chief objection to the method is the amount of labour thrown on the nursing staff, which is so considerable as to bar it from adoption as a routine. This should not, however, be allowed to prevent its use in the limited number of cases in which it is strongly indicated. These are:—