In many patients, dense scarring is found at the level of the stoma as well as at the site of postintubation stenosis. Scarring is heightened by prior surgical procedures. Normal subplatysmal anatomy is therefore identified first at the lateral ends of the transverse incision and dissection carried along the surface and border of the sternocleidomastoid muscles, both above and below on either side. The surgeon then works toward the midline and gradually elevates the skin and what is left of the platysma from the strap muscles and the midline points of adherence to the trachea. Initial dissection in almost every case is carried up to the level of the cricoid cartilage. A long-necked patient requires a longer horizontal incision so that the upper flap may be raised higher. I have avoided U-shaped incisions, which are less cosmetic and offer no better exposure. Inferiorly, the cutaneous and platysmal flaps are raised to the sternal notch. The anterior borders of the sternocleidomastoid muscles are followed to their attachments to the sternum. The anterior jugular veins are divided and raised with the flap superiorly. Inferiorly, they are usually left behind as the flap is elevated, or are redivided if the scarring is dense. The flaps are spread vertically with Gelpi retractors, exposing a field from cricoid cartilage to sternal notch (Figure 24-6).
The midline is identified above and below an existing stoma or a point of dense adherence to a prior stoma. The medial margins of the sternohyoid muscles are identified and elevated laterally for a short distance, followed by the sternothyroid muscles. The pad of fat, and often scar, which lies suprasternally is divided by dissecting beneath it, just above the sternal notch between the heads of the sternocleidomastoid
figure 24-6 Exposure of the cervical tracheal stenosis after spreading the collar incision vertically. Strap muscles are reflected laterally and held by a self-retaining retractor. The thyroid isthmus or its remnants are divided, suture-ligated, and retracted with traction sutures. Only thyroid adherent to anterolateral trachea is dissected at this point. The anterior surface ofthe trachea is dissected sharply from the cricoid to the sternal notch, and bluntly to the carina inferiorly. At this stage, only the anterior surface of the stenosis has been dissected.
muscles and superficial to the level of the strap muscles. This bundle of tissue may be divided between the clamps rather than by tedious dissection. Adherent strap muscles are dissected sharply from a stomal site. When a stoma is present, it is helpful to place hemostats for traction on either side of the ellipse of skin that has been left around the stoma. The anterior surface of the trachea must now be dissected. Above, the cricoid cartilage is usually identified in the midline and dissection carried onto the anterior tracheal wall immediately below it. It is usually possible to dissect beneath the remnants of the thyroid isthmus at the stomal area. If still intact, then the isthmus is sharply divided and suture-ligated on either side. The thyroid is dissected away from the tracheal wall on either side, but at this stage, only over the anterior portion of the tracheal surface. In order to reflect the isthmus completely, the pyramidal lobe is often divided just above the isthmus. Inferior to the point of maximal adherence, the anterior surface of the trachea is discovered. This is sometimes difficult, particularly where the trachea has been previously exposed surgically well into the mediastinum.
Decision is next made on whether or not an upper sternal division will be needed to enlarge surgical access. Even if a stenosis can be dissected without dividing the upper sternum, greater access will be needed for the anastomosis. Reconstruction will be completed with the neck in a slightly flexed position, with the chin brought toward the sternum. If it appears that the sternum will be better divided, then this should be done promptly in order to facilitate dissection. A vertical cutaneous incision is made from the midpoint of the collar incision down over the midline of the sternum to a point 2 cm below the sternal angle (Figure 24-7A). The substernal plane is bluntly dissected and the sternum divided vertically through the sternal angle. A small, pediatric-type chest retractor serves to spread the upper sternum several centimeters. One side or other of the divided portion of the sternum usually fractures at its lower end. No advantage is gained by deliberately dividing across one of the limbs of the partially divided upper sternum. Since all that is needed is access to the trachea behind the great vessels, complete sternotomy only extends the operative field without contributing to required exposure. Surface projection of the carina lies at the level of the sternal angle, but the carina rests posteriorly nearly against the vertebral bodies. After partial ster-notomy has been added, a single Gelpi retractor is placed with one point against either clavicular head and the other at the midpoint of the upper incisional flap (Figure 24-7B). Since a significant number of patients with tracheal stenosis acquired their lesions during treatment for complications of cardiac surgery, the hazards of reoperative sternotomy must be remembered. Careful technique, plus use of a Lebsche sternal knife and mallet instead of mechanical saws, will minimize these problems. Once in my experience, a cemented brachiocephalic vein was entered in such a case. Bleeding was controlled with Fogarty catheters while the vein was dissected free for definitive control.
The anterior tracheal surface is dissected completely from the cricoid cartilage to the carina, in most cases. The more normal segments of trachea above and below the stenosis and stoma are dissected first, often bluntly. Freeing the pretracheal plane will allow the trachea to slide more easily for anastomotic approximation. In contrast, a later freeing of the membranous wall of trachea from the esophagus will not greatly increase mobility, and hence it is done only to the limited extent needed to permit anastomosis. Due to the dense adhesions and unpredictable deformities seen with postintubation stenosis, dissection (especially after prior failed surgery) is guided by a combination of direct vision, palpation, and judgment from experience about where scar ends and the trachea or its stenotic remnants begin. Dissection proceeds from more normal trachea to scarred trachea. In the area of stenosis, dissection is kept very close to the scarred portion of the trachea and elsewhere against the trachea itself, in order not to damage recurrent laryngeal nerves. A stenosis may be indented in hourglass fashion. There may be no rings left to act as guides, and remnants of cartilages may be disordered. Traction sutures in the divided thyroid isthmus are useful as the gland is dissected from the lateral tracheal wall. Dissection of the normal distal trachea is done only on the anterior surface, once past the level of the lesion. Distal pretracheal dissection is done bluntly, as in medi-astinoscopy, if possible.
Great care must be taken not to injure the lateral blood supply of the portion of trachea that is to remain after resection of the lesion. Circumferential dissection of the trachea should be made only at the level of the lesion that is to be excised, and for no more than 1 to 2 cm above and below that level. Injury to blood supply may result in a later tracheal necrosis and severe restenosis, which may no longer be reconstructible. If a stenosis lies in the upper trachea, initial dissection is usually made circumferentially, immediately distal to the area of stenosis. A figure of 8 suture may be placed in the stenotic segment to facilitate retraction of the trachea, as dissection proceeds laterally and posteriorly on the trachea. Since the tissue below the stenosis is relatively normal, it is more easily dissected than that adjacent to the stenosis itself, particularly posteriorly. Circumferential dissection is done just below the lower border of the lesion. If the membranous wall is damaged during dissection, the perforation will be adjacent to the pathology and may be resected with the specimen. A lower or longer injury must be repaired. With delicacy and care, this will seldom occur.
figure 24-7 Cervicomediastinal exposure of a longer stenosis. A, The dashed line indicates the exploratory cervical incision. The vertical extension carried just past the sternal angle (solid linej provides the access to the mediastinum needed in this patient. B, A single Gelpi retractor exposes the cervical field. A pediatric chest wall retractor or a Tuffier retractor holds the sternal edges apart. In this patient, a stoma was present in the upper stenosis. Hemo-stats on the tips of the cutaneous oval around the stoma provide excellent traction later to rotate the trachea for dissection. The inferior Richardson retractor holds the undissected upper mediastinal vessels back to simplify lower pretracheal dissection. The distal trachea has not yet been exposed.
Esophageal injury is even less likely. If dissection proceeds easily around a circumferential stenosis itself, much or all of it may be completed before dividing the trachea. Otherwise, I prefer to divide the trachea just below the lesion, and elevate the specimen to facilitate completion of dissection (Figure 24-8A). In a supracarinal lesion, circumferential dissection is better done first just above the stenosis, and the trachea is divided proximal to the lesion (Figure 24-8B). Cross-field intubation in this case is done through the lesion, providing a good handle to facilitate distal dissection.
It is critically important to dissect close to the tracheal wall and to the lesion in cases of stenosis in order to avoid injury to the recurrent laryngeal nerves. Particularly in the upper trachea, these nerves lie in the tracheoesophageal groove. Dense peritracheal fibrosis may make it hazardous to try to identify the nerves or to isolate them in the vicinity of the lesion. To minimize the incidence of nerve injury, it is far better to dissect meticulously and patiently against the trachea without trying to visualize the nerves. The nerves remain in the scarred lateral tissues, which fall to either side. Elevation of the specimen with traction further protects the nerves during dissection, especially as the critical zone near the cricoid cartilage is approached.
Two major hazards of this dissection—devascularization of the trachea and injury to recurrent laryngeal nerves—have been emphasized. A third potential major hazard is injury to the brachiocephalic artery, which may result in postoperative hemorrhage. In many patients with a properly placed tracheostomy, the cuff will lie at the level of the innominate artery. Dense peritracheal fibrosis may form, where a subsequent stenosis lies directly behind the artery. In addition, if tracheal reconstruction has been attempted previously, the artery may have been dissected free, and may therefore be adherent to the trachea. In a number of earlier reports of upper tracheal resections, postoperative hemorrhage from the brachiocephalic artery occurred much too frequently. This complication is usually avoidable. The key principle is to dissect "hard against" the trachea, keeping the dissection on the tracheal surface or against the stenosis. No attempt should be made to dissect out the artery itself or to place loops around it for retraction. Dissection in this manner leaves a protective barrier of the artery's normal investments of connective tissue as well as scar tissue. If this technique is followed, then the artery is not likely to leak postoperatively, even when it lies against the anastomosis. In case of justifiable concern that the artery may be at risk, usually because of prior surgery, a strap muscle is pedicled and sutured between the artery and tracheal anastomosis to provide a buttress of healthy tissue. Less often, a lobe of thymus may be interposed. If the artery is fused to the trachea (due to prior surgery), proximal and distal control must be obtained before freeing it. In such cases, tissue interposition becomes essential.
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