Occasionally, as the upper muscle clamp is retracted upward and outward, a branch of the superior thyroid artery may be encountered, extending from the muscle to the surface of the thyroid gland in the region of the upper pole. This vessel should be carefully clamped and tied (Figure 22).
It is customary to begin a subtotal thyroidectomy at the right upper pole or on the larger side. Some surgeons prefer to divide the middle thyroid vein first (Figure 26), so as to improve mobility and exposure of the upper pole vessels. A narrow retractor is placed in the wound at the superior pole. Blunt dissection, which allows the thyroid capsule to be pushed away from the larynx, is best accomplished by opening a small, curved hemostat in the membranous tissue at this point (Figure 23). At the uppermost portion of the gland there is a thin fascia that almost encircles the trachea. This area must be clamped carefully, since it contains a small blood vessel that, if allowed to retract, is very dangerous to secure because of its proximity to the superior laryngeal nerve. Traction should be maintained on the thyroid gland by means of a curved hemostat or an umbilical tape snugged around the gland in the region of the upper pole. There is less chance of tearing a friable gland if curved hemostats or the umbilical tape, rather than a toothed tenaculum are used for traction. By sharp and blunt dissection the superior thyroid vessels are exposed well above their point of entry into the gland (Figure 23). The surgeon now decides whether to leave any thyroid tissue at the upper pole region and places the next clamp either at the upper limits of the gland or in the substance of the gland, perhaps 1 cm below the top of the pole. Hemostasis is effected more easily if the superior thyroid arteries are ligated extracapsularly. Moreover, if much glandular tissue is to be retained, it should be on the posterior surface at the level of the inferior thyroid arteries, as there is more likely to be a recurrence at the superior pole. Three small straight or curved hemostats are applied to the superior thyroid vessels. The vessels are divided, leaving one clamp on the thyroid side and two clamps on the vessels (Figure 24). The application of two clamps to the upper pole vessels permits a double ligation and lessens the possibility of active troublesome bleeding. Some surgeons prefer to make the second ligation a transfixing suture of fine silk (Figure 25).
If the middle thyroid vein has not already been identified and ligated, an effort should be made to locate this vessel. Often it is stretched to a thin strand as a result of traction applied to the gland in order to displace it (Figure 26). After the superior vessels and middle thyroid vein have been ligated, the narrow retractor is moved to the right lower pole, where the lower pole vessels enter the gland. These vessels are carefully freed from the adjacent structures, either with a small curved clamp or by finger dissection (Figure 27). Care must be taken not to injure the trachea at the time these vessels are divided and doubly tied (Figure 28). Occasionally, a venous plexus (or thyroidea ima) is found over the trachea entering the inferior surface of the gland in the region of the isthmus. This is carefully separated from the trachea with a blunt-nosed hemostat and ligated in the usual fashion.
As an alternative method, the surgeon may decide to start at the lower pole and luxate the gland before the upper pole is ligated. The thyroid tissue over the trachea is divided, and the right lobe is reflected outward (Figure 29). The lower pole vessels then are clamped and ligated. The middle thyroid vein is brought into view by medial retraction and can be tied easily. The upper pole is now freed by pushing the index finger behind the superior thyroid vessels. As the superior pole is pushed forward with the finger, a curved clamp may be inserted between the trachea and the medial surface of the superior pole, and the vessels can be doubly clamped (Figure 30).
After the middle and inferior veins have been ligated and the superior pole freed by either method, the next step is to expose the inferior thyroid artery. Traction is maintained anteriorly and medially as the artery is exposed on the lateral inferior surface of the gland (Figure 31). A narrow retractor is inserted laterally, and by gauze dissection the lateral aspect of the gland in the region of the inferior thyroid artery is visualized clearly. It should be remembered, especially in the presence of a large gland that has been displaced outward, that the recurrent laryngeal nerve may be much higher in the wound than ordinarily is anticipated. If a total lobectomy or extensive removal of thyroid tissue is indicated, it is necessary, by careful dissection, to identify this nerve, which may run between the bifurcation of the inferior thyroid artery as it enters the gland. The fossa posterior of the gland should also be inspected to determine, if possible, the location of the parathyroid glands, which are usually a pinkish chocolate color. Before commencing this dissection, it is wise to place hemostats on the vessels at the margins of the gland where the major branches of the inferior thyroid artery lie. The application of paired clamps to the major blood vessels at a safe distance from the region of the recurrent laryngeal nerve (Figure 32) defines the amount of thyroid tissue that will remain and lessens the chance of accidental injury to the nerve. With the trachea in view and the gland lifted into the wound, another row of small, curved hemostats is placed well into the parenchyma so that the desired amount of thyroid tissue is retained along with the posterior capsule (Figure 33). The amount of thyroid tissue allowed to remain in relation to recurrent laryngeal nerve is illustrated in Plate 184.