Anæsthesia has been divided into four clinical stages corresponding to the degrees to which the nervous system has been affected. The boundaries between these stages are often ill-defined, but the terminology has some value as facilitating description.
The First Stage lasts from the commencement of inhalation up to the time when volitional self-control is lost by the patient.
The Second Stage in the older text-books was said to be characterised by struggling, shouting, and breath-holding. With a patient not addicted to alcohol and with the anæsthetic skilfully administered, this description is unduly lurid.
The Third Stage is that of full surgical anæsthesia.
The Fourth Stage is that of over-dosage.
These give such valuable assistance to the anæsthetist that it will be well to define and describe them as a preliminary. They are three in number.
The Conjunctival Reflex is best elicited by drawing the upper lid upwards from the eyeball and retaining it in that position with one finger, while with another finger the ocular conjunctiva is lightly touched in the area of the inner canthus. If the anæsthesia is very light, both lids attempt to approximate and close the palebral fissure. The upper lid may slip down from under the retaining finger and come into its proper place, while the lower lid is elevated. At a deeper level of anæsthesia there is not complete action of the orbicularis but merely of a certain part of it, so that all that is observed is a twitch inwards of the lower lid. Even this form of the reflex disappears before the corneal reflex.
The Corneal Reflex is elicited by pushing up the upper lid by one finger and with the pulp of the same finger lightly brushing the centre of the cornea as soon as it is exposed, when we feel or see the upper lid come back into position with a sharp definite twitch. The examining finger must be slipped smartly out of the way as soon as the cornea has been touched. Even in deep anæsthesia, a trace of this reflex can usually be elicited if the little manipulation be properly performed.
The conjunctival and corneal reflexes are frequently confused in the mind of the student. The most common mistake made is to pin the upper lid firmly somewhere in the region of the bony roof of the orbit, to dab the eye far too vigorously, and to believe that no reflex is present because no movement of the upper lid takes place. In the first place, the upper lid cannot move if it is rigidly held against a bony plate: in the second place, it is wholly unnecessary to inflict upon the cornea more than the lightest of touches. Both these reflexes are to be used with great discretion, undue frequency and excessive vigour of touch being alike capable of setting up serious inflammatory reaction.
The Pupillary Light Reflex is elicited by shutting off light from both pupils for ten to twenty seconds and then smartly withdrawing the protecting fingers and allowing as strong a light as possible to fall on to the eye. The response of the ciliary muscle should always be present; its absence is a certain indication of something wrong: some sluggishness may be permissible under ether, but even that is suggestive of trouble if chloroform is the anæsthetic.
The use of a preliminary hypodermic of morphia tends to make the pupil somewhat smaller than normal, and to elicit the light reflex it may be necessary to cut off illumination for a somewhat longer period than if no morphia had been given. Nevertheless with a little care, the light reflex should always be capable of demonstration even in the morphinised subject.
In the case of nitrous oxide and of ethyl chloride, the patient passes through the various stages very rapidly, and the picture of anæsthesia as induced by either of these two is therefore best described separately. The following may be taken, therefore, as an account of what is to be observed in the patient inhaling ether or chloroform, unless a specific reference is made to one of the other anæsthetics.
First Stage.—The first sign that some effect is being produced in the patient is usually the appearance of the movements of swallowing; the hyoid and thyroid can be felt or seen to be moving in conjunction with the muscles of deglutition. During this stage, the patient being still to some extent under volitional control, there should be no other movement noticed. The eyes are usually closed and the colour normal; the respiration may be hurried by excitement, but judicious handling of the patient will do much to minimise this.
The Second Stage is really entered when volitional control is lost. It may be characterised by struggling and shouting by the patient, even if the anæsthetic is properly administered; but with a healthy patient and a good anæsthetist, all that usually occurs in the way of movement by the patient is some rigidity of the limbs and a slight attempt, perhaps, to lift the head from the pillow or a limb from the couch. The breathing tends during the first part of this stage to be light and is rarely entirely regular: slight pauses occur, usually after an inspiration, less commonly after expiration. Serious “holding of the breath” (after an inspiration) rarely occurs save in the type of patient who is also struggling; if it does occur to a degree which causes any blueness of the patient’s face (cyanosis), it usually calls for the removal of the anæsthetic for a moment until normal breathing has been resumed.
The colour of the face rarely departs much from normal during the second stage, unless cyanosis from breath-holding intervenes.
The eyes are usually opened, as the second stage progresses, and the eyeballs tend to rotate slowly in every plane. The pupils are usually large, but react sharply to light. Both conjunctival and corneal reflexes are brisk.
The Onset of the Third Stage is marked by the appearance of muscular relaxation. Any limb which the patient may have been holding rigidly up sinks down on to the couch, and it will be found that if an attempt be now made by the anæsthetist (as it should be) to turn the head of the patient to one side or another, the muscles of the neck no longer resist.
The respiration also alters in type, losing its tendency to lightness and irregularity, and becomes full, deep, and regular. In open ether anæsthesia particularly, expiration commonly assumes a “blowing” type very characteristic, and which to the trained ear is of itself an indication that full surgical anæsthesia is present or at any rate not far distant.
The colour varies somewhat with the anæsthetic in use. With ether it is usually somewhat higher than normal, and a trace of blueness may be present if the method is the “closed” one. Anything more than a trace, however, must be regarded as abnormal, whatever the method or anæsthetic may be. With chloroform the colour is perhaps a little paler than that normal to the individual.
The eyelids are usually half open, and the eyeballs at rest looking forward and slightly downwards. An extreme rotation downward may usually be taken as a sign of very deep anæsthesia. The pupil is, as already said, always active to light, but its actual size varies with the anæsthetic used. With ether, particularly “closed” ether, it may be large (4–5 millimetres): with open ether, preceded by morphia, about 3–4 millimetres: a good chloroform anæsthesia usually exhibits a pupil of only 2–3 millimetres, and if morphia has also been given, it may be pin-point in size. Too much emphasis must not be placed, however, upon the mere size of the pupil; that may vary within wide limits without necessarily indicating serious abnormality. The essential point is that the light reflex shall be brisk. A pupil of 5 millimetres reacting sharply to light may be of no special moment: one of that size immobile to light would cause real anxiety.
The conjunctival reflex usually disappears fairly early in the third stage: if briskly present, the anæsthesia is certainly a light one, and probably insufficient for an abdominal section. The corneal reflex if properly taken in the way already described can usually be elicited throughout the third stage. In an anæsthesia deep enough for abdominal section it is, of course, not brisk, but we may say generally that its entire absence is presumptive evidence of a very deep anæsthesia—probably undesirably deep. It must not be forgotten that some local causes such as drying of the surface of the cornea may cause it to disappear, and in case of doubt it is sometimes worth while to wash out the eye with a little saline solution. If after doing so the anæsthetist still finds the reflex not present he should be on his guard. Provided, however, that the light reflex is still present and colour and respiration satisfactory, he need not consider that the patient is in any immediate danger.
Broadly speaking, then, the third stage, the stage which is called for by the requirements of major surgery, is characterised by (1) full regular respirations; (2) colour not much removed from normal; (3) moderate sized pupil, larger in the case of ether than chloroform; (4) conjunctival reflex faint or absent; (5) corneal reflex just present, or, in a deep third stage, just absent; (6) light reflex present: these may be regarded as the signs of fully developed surgical anæsthesia.
The absolute beginner may be so completely out of his reckoning as to mistake the quietude of the later part of the first stage for the appearance of the third stage. For the prevention of so gross an error as that, the reader need only be referred to a patient study of the foregoing. But even a man with considerable experience may frequently be in doubt exactly as to how far through the third stage his patient has passed. He may have attained a level which will permit an incision to be made into the skin without movement on the part of the patient, but not one which would relax the abdominal muscles sufficiently for the peritoneum to be opened without eliciting considerable resistance from the abdominal muscles. In such moments of doubt, the author is accustomed to request the surgeon to make his skin incision, and observe the effect which this trauma has upon the depth, frequency, and regularity of respiration. This furnishes a most valuable guide to the depth of anæsthesia. In a third stage of very light degree, the respiratory rhythm will be interrupted and the breath held for a second in inspiration. Apart from any other sign, that may be taken as an index that the anæsthesia is very light—too light to permit of opening the peritoneal cavity. In a very deep anæsthesia the respiration is little affected by the skin incision, while at a moderate and more desirable level the respiration is quickened and deepened, but unaffected in the regularity of its rhythm.
The Fourth Stage is Stage of Over-Dose.—This stage is, of course, never entered voluntarily. Its earliest signs are loss of all tone in the muscles of expression, complete loss of corneal reflex, a widely dilated pupil insensitive to light, and a type of respiration which though definitely weakened may show occasional deep gasps. Circulatory failure and cessation of respiration from failure of the medullary centre are the closing phenomena of overdose.
It will be perhaps noticed that in the foregoing, no reference has been made to the examination of the pulse. This is not an oversight on the part of the author. It is perfectly true that under any anæsthetic not complicated by an asphysical element, the blood pressure falls as the drug takes effect, and that in the case of chloroform the fall is often quite considerable. Such a fall can be appreciated by the skilled finger, but only by concentrating upon that examination a degree of attention which necessarily detracts from the administrator’s available energy for the observation of other signs which are of equal value, and can be more rapidly and certainly appreciated and appraised.
It is nevertheless essential to assure oneself during the whole progress of an anæsthesia that the circulation is in a satisfactory condition. Two obvious guides to this are the colour of the patient’s face and the force with which cut arteries spout. As regards the colour in circulatory failure, one would naturally expect a pallid face, and this indeed is the rule. It must not be forgotten, however, that cyanosis may sometimes be cardiac in origin. Cases do sometimes occur when a bluish tinge is seen on the lips, ears, and nostrils, apart from any obvious cause of oxygen starvation. In these we may reasonably suspect that the right heart is failing, and take measures accordingly.
Another valuable index to the state of the circulation is the “skin reflex,” that is, the speed with which the circulation returns to an area of the skin which has been pinched. The student should train his eye by occasionally pinching the lobule of the patient’s ear and observing first the white area so produced, and later the rate at which, in a normal case, the healthy colour returns.
It is not intended to furnish here any account of matters more suitably treated under the “Accidents of Anæsthesia,” which are fully described in Chapter xvi., but merely to draw the attention of the student to certain departures from the normal course of anæsthesia which are encountered with varying frequency, to ascribe them as far as possible to their true causation, and indicate methods of prevention.
The abnormalities fall into two classes, those connected with the nervous and muscular systems, and those in which respiratory changes are evident.
Clonus or tremor sometimes appears in one or more limbs, even the trunk being affected in severe cases. Ether is practically the only anæsthetic under which the tremor ever appears, and the condition is often spoken of as “ether tremor.” It rarely appears in the female subject, being almost limited to powerfully built young men. Coming on towards the end of the second stage, it frequently persists in the deepest of third stages, and in bad cases there is usually no option but to change over to chloroform—always supposing that the tremor will interfere with the work of the surgeon. If it will not, the condition calls for no active treatment, since it is in itself not dangerous.
Movements recalling to the observer the condition of athetosis seen in the limbs of hemiplegics are occasionally seen in the anæsthetised patient. The fingers of a hand may be slowly moved, or one or other shoulder may be shrugged. The exact cause of these movements is obscure. They occur in all types, both sexes, and at all ages; they are not necessarily asphyxia though a trace of asphyxia seems sometimes to conduce to them. They persist for some time after the third stage has been entered, and ultimately disappear without any obvious cause other than the passage of time. It is rare for them to continue more than five or ten minutes after full anæsthesia has been induced. Their practical importance lies purely in this, that the inexperienced anæsthetist observing some muscular movements still persisting, may take them as an infallible sign that anæsthesia is not complete, and may deliberately take his patient to a deeper level. If in doubt, the anæsthetist must, of course, consult all the other recognised guides, such as the eye reflexes, but once he has seen these movements in a case, and had demonstrated to him their slow, rhythmical character, he is not likely to be misled on a future occasion.
Muscular rigidity has been mentioned already in Chapter iii. When it persists in a patient in whom other signs suggest that a full anæsthesia has been produced, the anæsthetist will usually find that attention to the air-way, and perhaps a whiff of oxygen, will remedy the trouble.
Shallow breathing or even slight temporary arrests of respiration arise frequently. During the induction stage they may be due to:—
1. Apnœa or acapnia following voluntary excessive breathing.
2. Using morphia before chloroform.
At a later stage, it may be due to:—
1. Acapnia following excessive breathing excited reflexly from the seat of operation.
2. Direct reflex inhibition of the respiratory centre. An example of this is seen sometimes when the bladder is over-distended by lotion.
3. Impending vomiting.
Moist sounds not uncommonly appear. The student’s general knowledge of medicine will enable him to decide whether the fluid is likely to be in the pharynx, larynx, trachea, or bronchi. If in one of the first two named, it will suffice to swab out the throat and encourage the patient to cough. If, however, moisture is evidently present in the trachea or bronchi, the condition is one calling for considerable care and judgment. It arises more commonly with ether than with chloroform. Much will depend upon how much longer the surgeon requires to finish his operation. If only a few minutes more are required, nothing is necessary but to cut down the amount of ether being given to the minimum possible. If, however, the surgeon has still a good deal to do, the safest thing is to withdraw the ether and substitute chloroform or a mixture. Be it clearly understood, however, that such a change over is not devoid of risk. If it is to be made, it must be done early, before the patient is cyanosed and almost drowned in his own secretion. In a neglected case where cyanosis has already appeared, there will be no option but to interrupt the operation, empty the chest by encouraging coughing, and to aid the process by compressing the patient’s chest during expiration. Thereafter chloroform may be given, but with the greatest care.
Gasping and sighing are not common phenomena but when they occur, call for close notice from the anæsthetist. Excluding, of course, such occurrences in the first stage, before volitional control has been lost, they may be usually but not invariably ascribed to overdosage or to the appearance of definite surgical shock. Whenever they are noticed, therefore, it behoves the administrator to overhaul the patient thoroughly, to consult the eye reflexes, the skin reflex, and the pulse, and not to rest until he is assured that there are no other signals of danger to be found.
Stertor and stridor. The first of these is caused by flapping of the soft palate. It is a noise low in pitch, resembling ordinary snoring. Indicating as it does that the palatal and therefore probably other muscles, are relaxed, it may if moderate in volume usually be taken as a favourable sign. If it becomes very loud, however, the probability is that the base of the tongue has fallen back; cyanosis will begin to appear, but will immediately be remedied by pulling forward the jaw or in extreme cases, using the tongue forceps.
Stridor is a high-pitched sound produced by approximation of the vocal cords. It has already been dealt with in Chapter iii.
This term has been applied to a condition often seen in children, and occasionally in adults. It is almost limited to chloroform: the author has never seen a genuine case when ether has been in use. It appears very quickly after inhalation has begun: the muscles are relaxed, the respirations quiet and regular, the conjunctival reflex sluggish. A very marked feature is the excessive smallness of the pupil. Obviously then, the condition much resembles a true third stage, but if the operation be begun, the mistake will very rapidly be made evident, for the patient will at once move and cry out. In essence, the condition is simply one of ordinary sleep. It can be recognised by its appearance after a period of inhalation too brief for the induction of true anæsthesia, by the very small pupils and the lightness of the respiration. It will be a waste of time to permit the condition to continue, as the lightness of the respiration delays the taking in of a dose of the anæsthetic sufficient to induce a proper third stage. The remedy is simple,—rub the lips and face smartly with a towel or the hand, when respiration will at once deepen and the pupil dilate. Thereafter, the induction should proceed normally.