—The common carotid may be tied above or below the omohyoid. The carotid divides at the level of the thyroid prominence, and it is more easily exposed above the omohyoid than below. It may be reached by an incision, 10 Cm. in length, along the anterior border of the sternomastoid, whose centre should be at the level of the intended ligature. The sternomastoid, after exposure, is drawn outward and the other muscles inward; bleeding veins are secured; the artery recognized by its pulsation; its sheath opened, preferably on the inner side, and the needle passed from within outward, the operator taking pains to avoid the descendens noni. The internal jugular is more likely to be in the way and to need retraction on the left side than on the right. In this operation when the omohyoid is exposed it is retracted upward.
Through this exposure temporary occlusion, either by provisional ligation or the employment of Crile’s clamps, may be practised.
Ligature above the omohyoid is performed in the same way, the veins being divided and secured. The omohyoid is now drawn downward and the other muscles separated as above. The so-called carotid tubercle is the anterior projection of the transverse process of the sixth vertebra, and the ligature is usually applied at the point where the vessel can be felt pulsating upon this prominence. The same care should be exercised in avoiding the descendens noni. Nélaton is reported to have said that it would take a man four minutes to bleed to death after opening the carotid artery, but it should take only two minutes to tie it.
The External Carotid.
—The incision now is placed higher, from the angle of the jaw to the level of the cricoid cartilage, still along the anterior border of the sternomastoid, which is to be retracted outward. The posterior belly of the digastric will now appear, with the hypoglossal nerve below it, both being carefully avoided. The great cornu of the hyoid being sought and found, the artery is found opposite its tip, and ligated between the superior thyroid and the lingual branches, or perhaps below the latter. The superior laryngeal nerve which passes behind the vessel is to be scrupulously excluded.
Excision of the external carotid has been recommended, especially by Dawbarn, for the purpose of cutting off the blood supply from certain inoperable cancers of the tongue, face, and jaws. He regards mere ligature as insufficient and insists that, since anastomosis is perfected too soon after the other procedures, it is necessary to completely excise a portion of the vessel. He does this first on the side most affected, and then, say a few weeks later, attacks the other side. He advises to ligate the external carotid just beyond its origin, to divide it, to seize the upper end in forceps, and then, controlling the vessel, to isolate it up to a point where it disappears in the substance of the carotid, tying each branch as it is exposed. He would again tie it just below the origin of the internal maxillary and temporal branches.
The Internal Carotid.
—The internal carotid is very rarely attacked in this way. It lies at first to the outside and back of the external carotid, and here it may be sufficiently exposed to admit of ligation. The incision does not differ essentially from that for the external carotid. After the vessels are exposed the external branch should be drawn inward, the digastric upward, or divided, if necessary, and the needle passed from without inward, avoiding the jugular and the vagus ([Fig. 162]).
Fig. 162
