Part 80 (1/2)
(xi) _Sudden dyspna during surgical operations_, due to--
(_a_) Mechanical obstruction to respiration, such as is caused by impaction of foreign bodies within the larynx (tooth-plates, teeth, blood, pus, vomited food, &c.), by faulty position of the head or falling backwards of the tongue, by a swollen condition of the larynx, by tumours or abscesses (retropharyngeal) which obstruct the air-way, by cicatricial contraction of the pharynx or larynx, by paralysis of the vocal cords, or by spasm of the muscles of the jaws so often a.s.sociated with a similar condition of the glottis and auxiliary muscles of respiration. In a case reported by Boyle, a well-nourished muscular man was anaesthetized for the operation of internal urethrotomy; considerable difficulty was encountered with his breathing, and only towards the end of the operation was it discovered that he had well-marked stenosis of the upper opening of the larynx.
The entrance into the larynx of vomited food or blood is certainly dangerous, and may occur during the simplest operations even when properly performed, as, for instance, during removal of tonsils or adenoids. It is more likely to occur if the patient has not been prepared for an anaesthetic, or if the latter be badly administered, if the laryngeal reflex be lost, if the patient be in a bad position or suddenly moves, or if the surgeon allows too much blood to collect in the pharynx.
(_b_) Failure of respiration from an overdose of chloroform or other anaesthetic. To remedy such conditions it is essential that the air should be expelled from the chest as rapidly as possible. Artificial respiration can only be successful when the air pa.s.ses freely both into and out of the lungs: in rare instances there may be so much difficulty in maintaining a free pa.s.sage that tracheotomy should be performed.
(xii) _Multiple papillomata of the larynx._ Here tracheotomy is required for the relief of dyspna and as a preliminary to other operations. It has also been suggested as a method of curing the papillomata by giving rest to the larynx. After the performance of tracheotomy the congestion is relieved and the growths decrease in size; in some cases they completely disappear, but the treatment is uncertain and not to be recommended (see p. 485).
(xiii) _Malignant disease of the pharynx or larynx which is too advanced for other forms of treatment._ Palliative tracheotomy may be employed in order to relieve dyspna or as a means of giving rest to the larynx. It is most commonly used for cases of extrinsic carcinoma of the larynx: thus C. Jackson reported twenty-nine such cases, in twenty-one of which he advised palliative tracheotomy and in only eight laryngectomy. Of the former, tracheotomy was actually performed in nine, but none of the patients lived for more than thirteen months. It seems doubtful whether tracheotomy has any marked effect in r.e.t.a.r.ding the course of malignant disease, though it sometimes gives relief.
(xiv) _Foreign bodies in the air-pa.s.sages._ It makes no difference what views are held as to the advisability of tracheotomy in the treatment of these cases. The fact remains that the first essential is the safety of the patient, and, if the dyspna is urgent, relief must be afforded.
When a foreign substance has been inhaled the surgeon must always be prepared for tracheotomy, and it is not advisable for him to leave the patient, even for a short interval, without proper supervision. In addition, the operation has been advocated as the proper treatment for all cases of foreign bodies in the lower air-pa.s.sages: nevertheless, removal by Killian's method gives far better results (see p. 559).
(xv) _As a preliminary to operations upon the upper air-pa.s.sages_ tracheotomy is rarely necessary, its place having been taken by infrathyreoid laryngotomy: it is, however, often performed before undertaking the larger operations upon the larynx (see p. 489).
=Anatomy.= The length of the trachea of an adult is about 4-1/2 inches, of which 2-1/2 inches lie above the level of the sternum; the cervical portion, which consists of eight or more rings, extends from the cricoid cartilage above to the suprasternal notch below. In order to determine the upper limit of the trachea it is advisable to palpate the following structures, which lie in the middle line, from above downwards: namely, the hyoid bone with its greater cornua, the thyreoid cartilage which forms the greatest prominence on the front of the neck, and the cricoid cartilage; in this manner it is possible to detect whether there is any deflexion of the trachea from the middle line as the result of a tumour lying in one side of the neck.
The anterior border of the sterno-mastoid muscle on each side is also an important landmark; the two muscles approach each other as they descend to their attachments to the sterno-clavicular joints, thus forming an angle the position of which corresponds to the notch in the manubrium sterni. By drawing a line transversely across the cricoid cartilage to the anterior borders of the sterno-mastoid muscles, a triangular s.p.a.ce is marked off which may be described as the _tracheotomy triangle_ (Fig.
264).
Beneath the skin and superficial fascia lie the two anterior jugular veins; these run from above downwards, to communicate with a branch which crosses the middle line of the neck, commonly in the lower part of the tracheotomy triangle, and there is an interval between them which is, in most cases, sufficiently large to prevent their being injured by a central incision. The pretracheal muscles, namely, the sterno-hyoids and sterno-thyreoids, are closer together; but the interval can be recognized by the greater thickness of the deep fascia which pa.s.ses between them. When the latter is incised, these muscles can be separated, and the trachea is exposed, together with the structures that lie on its anterior aspect. These are the following:--
[Ill.u.s.tration: FIG. 268. ANATOMY OF THE LARYNX AND TRACHEA AND THE POSITION OF INCISIONS FOR THE OPERATIONS IN THIS REGION. A, Subhyoid pharyngotomy; B, Thyrotomy; C, Infrathyreoid laryngotomy; D, 'High'
tracheotomy; E, 'Median' tracheotomy; F, 'Low' tracheotomy; 1, Platysma; 2, Crico-thyreoid muscle; 3, Sterno-hyoid muscle; 4, Isthmus of thyreoid gland; 5, Sterno-thyreoid muscle; 6, Sterno-mastoid muscle; 7, Crico-thyreoid artery; 8, Anterior jugular vein; 9, Inferior thyreoid vein; 10, Innominate artery; 11, Right innominate vein; 12, Left innominate vein.]
(_a_) _The isthmus of the thyreoid gland_, which varies greatly in size.
It may be either a thin band with few vessels of importance, covering the second, third, and fourth tracheal ring; or hypertrophied and vascular, extending higher in the neck even to the front of the cricoid or thyreoid cartilage. This condition also results when a pyramidal lobe is present.
(_b_) _The pretracheal fascia_, which encloses the isthmus of the thyreoid gland and, when traced upwards, finds attachment to the anterior aspect of the cricoid cartilage, thus forming the suspensory ligament of the isthmus. Pa.s.sing downwards it covers the anterior surface of the trachea, and, though somewhat indefinite, can easily be traced behind the sternum as far as the pericardium, with which it blends. This is a point of great practical importance in determining the extension of inflammation into the mediastinum.
(_c_) _Veins._ Small transverse branches of the superior thyreoid veins run upon the upper border of the isthmus between the layers of the fascia which surround this structure. The inferior thyreoid veins, larger in size, run from the lower border of the isthmus vertically downwards in front of the trachea to communicate with the left innominate; in their upper part they may consist of several small veins which join together to form two main branches, of which the left may lie directly in the middle line; small communicating branches of these veins run transversely across the lower border of the isthmus. The left innominate vein crosses the front of the trachea somewhat obliquely, and may lie at least half an inch above the suprasternal notch.
(_d_) _Arteries._ The crico-thyreoid artery runs transversely across the crico-thyreoid s.p.a.ce, being placed in front of the suspensory ligament, and gives off numerous branches, which enter and supply the interior of the larynx, as well as small descending branches which run to the isthmus of the thyreoid gland. A small branch of the inferior thyreoid artery is also constantly found behind the isthmus, and in rare instances a thyreoidea ima branch of the innominate, varying greatly in size, may pa.s.s upwards in front of the trachea.
In young children the same relations are found, but with certain differences. Owing to the larynx being relatively high in the early years of life, the length of the cervical portion of the trachea is almost 2 inches when the head is extended, and the bifurcation is considerably higher than in the adult; further, the trachea is more movable and is smaller in diameter. The laryngeal cartilages are difficult to distinguish, but a ma.s.s composed of the thyreoid and cricoid cartilages can always be felt, and its position determined by careful inspection. It is very important to remember that, even when the head is extended, the cricoid cartilage lies rather less than 2 inches above the upper margin of the sternum. In very young children it is common to find two transverse creases in the skin, of which the upper usually lies over the upper border of the thyreoid and the lower over the cricoid cartilage. The lower crease thus a.s.sists in determining the upper limit of the trachea.
The anterior jugular veins in young children are comparatively large; the infrahyoid muscles are less defined and more difficult to recognize; and the isthmus of the thyreoid gland is very broad, appears to be part of the lateral lobes, and occupies a higher position in the neck, often pa.s.sing in front of the crico-tracheal membrane as well as the first and second tracheal rings. The inferior thyreoid veins are larger, more numerous, and more difficult to separate; the left innominate vein is somewhat higher in the neck; the thymus gland, which gradually decreases in size with the increase of age, may extend into the neck, in front of the trachea, and may even reach as high as the isthmus of the thyreoid; the fasciae are softer and less definite, and the fascia which covers the trachea is easily stripped from its surface.
TRACHEOTOMY IN DIPHTHERIA
=Operation.= As local anaesthetics are of little practical value in the case of children, the surgeon must decide whether a general anaesthetic shall be used; for any nervousness on his part increases the danger of death upon the table. A general anaesthetic is not necessary, but undoubtedly has certain advantages: the operation is easier and can be performed more rapidly; the patient is more likely to fall asleep; and any vomiting that occurs is beneficial rather than harmful. On the other hand, children suffering from diphtheria are apt to die suddenly under chloroform; and it should never be administered when there is any sign of heart failure, when obstruction is very marked, when cyanosis is present, or when the patient is prostrate. The danger has probably been exaggerated, and depends more upon the experience of the anaesthetist than upon the actual disease; in my opinion it is as a rule safer to employ a small quant.i.ty of chloroform, which should be given on the operating table after everything has been prepared. The child should be allowed to choose its own position, generally curled up on one side, and the administration must be slow. By observing these precautions it usually happens that the child becomes quiet, and that with the loss of consciousness the breathing improves; the child can then be placed in the proper position, and the more difficult part of the operation can be completed before restlessness returns.
The instruments required are: a small scalpel, scissors, two dissecting forceps, three or more fine-pointed pressure forceps, two double hook retractors, one blunt hook, an aneurysm needle, and a suitable dilator for the wound; some form of aspiration apparatus may also, in rare instances, be necessary (Fig. 278). Three or four tracheotomy tubes such as described by Parker, and a small tube containing sterilized catgut, which is eminently suitable for the tying of vessels, and for that purpose preferable to silk, should also be in readiness. All the instruments should be kept together in a metal case, as well for private as for hospital practice, so as to be ready in case of emergency. They should be boiled for at least twenty minutes both before and after each operation, and should be laid out separately upon a dry sterilized towel in the position selected by the surgeon.
[Ill.u.s.tration: FIG. 269. TUBES FOR TRACHEOTOMY. A, Parker's; B, Durham's; C, Baker's rubber tube.]
Tracheotomy tubes may be made of silver, rubber, vulcanite, celluloid, or a gum-elastic material, but most surgeons prefer a silver tube in the early stages of treatment. An angular form should be used, for 'with the ordinary quarter circle tube, the lower extremity tends to impinge on the anterior wall of the trachea, and this is attended with many inconveniences and even with grave risks' (Parker[27]). A movable s.h.i.+eld is equally important, and this should be flush with the neck in order to avoid the possibility of its being removed by the patient. Further, the tube should consist of two parts--an outer tube to which the s.h.i.+eld is attached, and an inner tube which projects slightly beyond the outer and can be removed for purposes of cleaning. To encourage breathing through the larynx, a window may be added in the upper part of the tubes.
Parker's tube, which meets all the above requirements, is the one most commonly used in England. When longer tubes are necessary, either Durham's or Stewart's is recommended: in these, the position of the s.h.i.+eld can be altered, and the length of the tube arranged, to suit the patient. In cases of long duration the use of rubber tubes such as Morrant Baker's is indicated. An introducer is rarely necessary except for rubber or long tubes. As taper and bivalve tubes are liable to injure the trachea, their use is not advised. The tube chosen should fit loosely, and should project far enough into the trachea to be secure from slipping out during coughing or struggling. Short tubes are preferable, and the wider the tube the easier the breathing and the better the drainage. The approximate diameter of the trachea varies at different ages, and the size of tube suitable in each case varies chiefly according to the trachea, but partly also according to the fatness of the neck. The accompanying table indicates the appropriate dimensions.
[27] _Tracheotomy in Laryngeal Diphtheria_, 2nd ed., p. 42.
TABLE SHOWING SIZE OF TRACHEA AND OF TUBE REQUIRED AT DIFFERENT AGES
+--------------+------------+------------+---------------------+
_Approximate
_Approximate
_Number of tube._
_Age._
diameter of
diameter of+----------+----------+
trachea._
tube._
_Parker's_
_Durham's_
+--------------+------------+------------+---------------------+
6 months
4 mm.
4 mm.
16
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