Peirong Yu and Garrett L. Walsh
INDICATIONS/CONTRAINDICATIONS
Indications
Tracheal defects may result from surgical resection of primary tracheal tumors or secondary tumors involving the trachea, congenital anomalies such as tracheal atresia, traumatic defects, and trachea malacia or strictures from prolonged intubation. Tumors of the trachea can be primary or secondary. In our practice, the most common tracheal lesions are the result of advanced thyroid cancer involving the trachea.
Small windows of the trachea can be patched or closed primarily. Short tracheal defects may be closed primarily with or without mobilizing the right hilum and laryngeal release. It is generally accepted that a tracheal defect longer than 5.5 cm may not be closed primarily and therefore reconstruction with a tracheal conduit will be required. In cases where patients have had either previous neck surgery or irradiation or are elderly, even a 4–5 cm defect may not be able to be closed primarily due to tracheal calcification, fibrosis and reduced elasticity and blood supply. Therefore, any long tracheal defects that cannot be safely closed primarily are indications for microvascular tracheal reconstruction.
The ultimate goal of tracheal reconstruction is to provide a noncollapsible airway, with a stable epithelial lining and reliable, well-vascularized tissue coverage. Our preferred approach is to use a vascularized radial forearm fasciocutaneous flap for epithelial lining and a prosthetic material for rigid support. A well-vascularized muscle flap may also be necessary to provide coverage to protect the neotrachea as well as great vessels. This is particularly important when postoperative radiotherapy is planned.
Contraindications
Contraindications for complicated tracheal reconstruction can be systemic or local. Severe systemic comorbidities such as major cardiovascular and pulmonary diseases may result in life-threatening complications. Thus, complex reconstruction should be avoided in these patients who may be a prohibitive risk. Locally, if the larynx is already compromised as a result of a radiation stricture or if the resection margin is too close to the vocal cords, preservation of the larynx may result in a poor functional result. Placing sutures through a calcified thyroid cartilage is extremely difficult and may increase the risk of an air leak or dehiscence. The presence of unilateral vocal cord paralysis in these patients may cause further respiratory decompensation. These patients may be better served with a total laryngectomy. It should be pointed out; however, that unilateral vocal cord paralysis alone is not a contraindication to this procedure.
PREOPERATIVE PLANNING
Tracheal reconstruction requires careful planning and a team effort with experts from many disciplines. These include head and neck surgery, thoracic and cardiovascular surgery, reconstructive surgery, critical care, and anesthesiology, as well as specialty nursing care for the early recognition and the avoidance of life-threatening complications. Anesthesiologists must have experience in airway surgery and a good basic understanding of the sequence of tracheal reconstruction and be prepared to frequently change the endotracheal tube during surgery. Surgeons from different services, including reconstructive surgery, must be familiar with airway management as well as bronchoscopy techniques. Many patients have unilateral vocal cord paralysis, which further complicates surgery by increasing the risk for aspiration and airway compromise. Major tracheal surgery and reconstruction thus should be performed in specialized centers with expertise from multiple disciplines.
A thorough evaluation of the extent of disease involvement or defect of the trachea should be performed with imaging studies and bronchoscopy. The status of the remaining airway and lung functions should also be evaluated. For lesions in the cervical trachea, disease involvement of the larynx and vocal cord function are carefully assessed. A history of external beam radiation greatly increases the degree of difficulty in the surgical dissection and the surgical risks. The field of radiation should be obtained for reconstructive planning. A history of neck dissection, especially a combination of neck dissection and external beam radiation, may result in the lack of recipient vessels for microvascular reconstruction and pose significant risk for major blood vessel blowouts during surgical dissection of the trachea and recipient vessels. Vascular status in the neck and upper chest should be evaluated with CT angiography (CTA).
The radial forearm donor site needs to be carefully evaluated for history of trauma, hand dominance, and vascular dominance. The forearm on the side of the patient’s nondominant hand is chosen. An Allen test is commonly performed to assess the integrity of the palmar arches although its reliability is questionable. A normal Allen test usually indicates an intact palmar arch and the radial forearm flap can be safely harvested. In patients with an abnormal Allen test, the radial forearm flap can still be safely harvested in most patients. However, radial artery reconstruction with a saphenous vein graft should be prepared in case the hand perfusion is compromised after harvesting the flap. Once the side of the radial forearm flap is decided in the outpatient setting, patients are advised not to have blood drawn or intravenous lines or arterial lines placed in that arm prior to the surgical date.
The availability of prosthetic material for rigid support should be confirmed. A Montgomery T tracheostomy tube should also be available.
SURGERY
Routine deep vein thrombosis prophylaxis is given according to the risks and guidelines. Prophylactic antibiotics are also given before making an incision and redosed accordingly.
Positioning
If thoracotomy is not required, patients are placed in a supine position. The head, neck, and chest are surgically prepared. The nondominant forearm is also prepared, wrapped with sterile sheets, and secured on the abdomen. The ablative surgeons perform the resection of the tracheal pathology and the tracheal defect is created. At this point we harvest the radial forearm flap. The arm is placed on an arm board taking care not to extend the arm beyond 90 degrees. Harvesting the radial forearm flap is usually performed in a sitting position.
Techniques
Evaluation of the Defect
Once it is determined that primary end to end anastomosis is not possible, free flap reconstruction is planned. The length and width (circumference) of the defect is measured. The proximal extent toward the larynx and the distal extent toward the carina are assessed (Fig. 43.1).
Preparation of Recipient Vessels
For most tracheal defects, reconstruction can be performed through the neck incision with or without removing the clavicular heads and manubrium. Recipient vessels for microvascular anastomosis are usually readily available in the neck. The superior thyroid artery and a branch of the common facial vein stump that drains into the internal jugular vein are commonly used as recipient vessels. Alternatively, the transverse cervical artery and vein lower in the neck can be used. The third option is the internal mammary artery and vein if the clavicular head and manubrium are removed. The distal part of the recipient artery and vein are clipped or ligated. The proximal stump of the recipient vessels are occluded with a Biover microvascular clamp or Acland vascular clamp with a clamping force of 20 to 30 g/mm2 before dividing the vessels. The clamping and division of the recipient vessels can also be performed after the radial forearm flap is harvested to minimize clamp time. The arterial inflow is checked by releasing the clamp to ensure that pulsatile flow is present.
Figure 43.1 A tracheal defect following resection of a recurrent papillary thyroid cancer. The defect extends from the thyroid cartilage to 5 cm above the carina and involves three quarters of the circumference.
Figure 43.2 The PolyMax mesh is placed in a water bath with the water temperature at 70°C. Once it becomes soft, a tubular structure can be formed over a large syringe with a diameter of 30 mm.
Preparation of the Prosthetic Material
Although there are numerous FDA-approved prosthetic and bioprosthetic materials available, we have not found an ideal one. The ideal material should be semirigid, noncollapsible yet flexible; porous to allow easy tissue ingrowth and integration; and should have a diameter of 30 mm to allow the radial forearm flap to be placed inside for lining still leaving an adequate lumen to breathe through. If a 20-mm diameter of final airway is desired, the thickness of the radial forearm flap with a certain degree of swelling will account for at least 10 mm; thus, a 30-mm diameter of prosthesis is required. Of the many FDA approved, commercially available prosthetic materials tested in animal models, we eventually chose the combination of a 26-mm-diameter Hemashield vascular graft (Boston Scientific, Natick, MA) reinforced with a sheet of 0.5-mm-thick PolyMax resorbable mesh (Synthes, Paoli, PA). We also tested the polytetrafluoroethylene (PTFE, Gore-Tex) ring vascular graft (W. L. Gore & Associates, Inc., Flagstaff, AZ) and found that the Gortex graft had very poor tissue integration and was prone to exposure and infection.
The Hemashield graft is porous and allows excellent tissue integration. However, it is rather soft and easily collapsible. Therefore, it needs to be reinforced with a more rigid mesh material, the PolyMax mesh. The PolyMax mesh with the desired width and length is placed in hot water (>70°C) in a sterile water bath. Once it becomes soft in hot water, the sheet of mesh is placed on a large sterile syringe with a diameter of 30 mm to form a semicircular tube (Fig. 43.2). The mesh hardens in room temperature. Additional trimming can be easily done with a pair of suture scissors.
To increase the diameter of the 26-mm Hemashield graft, the graft is longitudinally opened (Fig. 43.3). The 30-mm-diameter semicircular PolyMax mesh (approximately three quarters of circumference or appropriate size for the defect) is now placed inside the Hemashield graft and sutured together with several 3-0 polypropylene (Prolene) sutures (Ethicon, Somerville, NJ). This forms the final supporting material for the neotrachea.
Figure 43.3 A Hemashield aorta graft with a diameter of 24 mm is longitudinally opened and trimmed to the appropriate length.
Figure 43.4 The radial forearm flap based on the radial artery and venae comitantes is harvested from the non-dominant forearm. Suprafascial dissection is performed to minimize tendon exposure.
Harvesting the Radial Forearm Flap
Harvesting the radial forearm flap is performed under tourniquet control with a cuff pressure of 100 mm Hg above the systolic pressure, usually at 250 mm Hg. The dimensions of the flap are outlined according to the size of the defect with the distal border of the flap near the wrist crease. A small incision is first made over the radial vessels at the wrist crease to explore the radial artery and venae comitantes. If one of the venae comitantes is larger than 1-mm diameter at the wrist level, the cephalic vein is not needed for venous anastomosis. The venae comitantes are preferred by the first author as the drainage vein. The radial vessels are then ligated and divided. The flap is raised in a “suprafascial dissection” technique to minimize tendon exposure and injury to the branches of the radial sensory nerve (Fig. 43.4). The incision is extended toward the antebrachial fossa to expose the bifurcation of the radial artery and the common trunk of the venae comitantes. A proximal skin perforator is recruited to support a separate small skin paddle for flap monitoring purpose (Fig. 43.5). Once the flap is completely islanded on the vascular pedicle, the tourniquet is released and perfusion to both the hand and flap are ensured before the vascular pedicle is ligated and divided. The forearm donor site is covered with a full-thickness skin graft (preferred) harvested from the lower abdomen or groin, or with a split-thickness skin graft from the thigh. The skin grafts are pie crusted, covered with Xeroform gauze and a Reston foam dressing. The forearm is immobilized using a dorsal splint for 6 days.
Assembly of the Neotrachea
The radial forearm flap is placed inside the prosthetic construct, with the skin side facing the lumen (Fig. 43.6). The flap is suspended to the construct with several rows of 3-0 polypropylene sutures through the dermis of the flap. These suspension sutures should be placed away from the vascular pedicle and are loosely tied to avoid vascular compromise of the flap (Fig. 43.7). A small window is created at the end of the prosthesis where the vascular pedicle will be brought out. The final neotrachea is now ready for transfer.
Figure 43.5 A second skin island of the radial forearm flap can be fashioned based on a proximal perforator. This skin island can be externalized for flap monitoring purpose.
Figure 43.6 The PolyMax mesh is placed inside the Hemashield graft. The radial forearm flap is then placed inside the PolyMax mesh for lining with the skin surface facing the lumen.
Insetting and Revascularization of the Neotrachea
The neotrachea is placed over the tracheal defect with the vascular pedicle coming out on the laryngeal end. The radial forearm flap is sewn to the remaining tracheal wall on the recipient vessel side first using 3-0 vicryl sutures (Fig. 43.8). Vascular anastomoses are then performed under an operating microscope using 9-0 Nylon sutures for the artery and a Synovis venous coupler (Synovis Micro Companies Alliance, Inc., Birmingham, AL) for the vein. Once the neotrachea is revascularized, the remaining flap insetting is completed (Fig. 43.9). The patient is allowed to breath spontaneously at this point. The endotracheal tube is withdrawn above the tracheal defect. A Montgomery T tracheostomy tube is inserted into the neotracheal lumen between the distal end of the flap and the native trachea. The prosthetic material around the T-tube is trimmed back for a few millimeters, so that it is not exposed to the tracheostomy site. The endotracheal tube is completely withdrawn. Bronchoscopy is performed through the T-tube to evaluate the reconstruction and airway patency. The T-tube is an important temporary measure to “stent” the lumen to prevent occlusion from flap swelling and to avoid high airway pressure during coughing, which may cause an air leak or an anastomosis disruption.
Coverage of the Neotrachea
The prosthesis should be covered with well-vascularized tissue on the outside. This can be accomplished with either a sternocleidomastoid muscle or a pectoralis major muscle flap. The latter is preferred in patients with a large neck and extensive lymph node dissection (that leaves some dead space) around the trachea or in a previously irradiated neck. The muscle flap covers the entire tracheal reconstruction and wraps around the T tracheostomy tube (Fig. 43.10). A 15-Fr Blake drain is placed on each side of the neck. The small monitoring skin flap based on a proximal perforator vessel is brought outside the neck through the neck incision for flap monitoring purpose (Fig. 43.11). Alternatively, flap monitoring can be achieved with a Cook Implantable Doppler device, or the Synovis Flow Coupler device.
Figure 43.7 The radial forearm flap is suspended to the PolyMax mesh and Hemashield graft with 3-0 Prolene sutures. These sutures are placed through the deep dermis of the forearm flap. Several rows of these sutures can be placed with care not to place the sutures near the vascular pedicle.
Figure 43.8 The construct consisting of the radial forearm flap, Hemashield graft, and PolyMax mesh is sewn to the tracheal defect.
Figure 43.9 The proximal end of the forearm flap with the vascular pedicle is oriented toward the larynx. Extra adipofascial tissue from the proximal forearm flap is used to cover the thyroid cartilage. The vascular pedicle is usually anastomosed to the superior thyroid artery, the facial vein, or the transverse cervical vessels.
Figure 43.10 The pectoralis major muscle flap is used to cover the entire reconstruction. A T-tracheostomy tube is placed in the inferior end of the construct. The pectoralis major muscle flap wraps around the T-tube to promote healing after decannulation.
Figure 43.11 The second skin island of the radial forearm flap is externalized for flap monitoring. The T-tracheostomy tube is in place.
The neck is irrigated with an ample amount of normal saline and returned to a neutral position. The vascular pedicle and anastomoses are inspected to ensure that there is no kinking, twisting, or compression of the vascular pedicle before closure of the neck incision. A Dobhoff feeding tube is placed for temporary feeding during the acute postoperative period.
POSTOPERATIVE MANAGEMENT
Meticulous perioperative care is given as part of a combined team effort. Patients are placed in a surgical ICU for close monitoring of their airway. Since there is no cuff on the T tracheostomy tube to provide positive ventilation, patients are awakened and must be breathing spontaneously at the time of placing the T-tube and kept awake throughout the postoperative period. Bronchoscopy through the T-tube is performed daily for 3 days to assess flap viability and airway patency and to clear secretions.
Because many patients have unilateral vocal cord paralysis, a bedside swallowing test is given to all patients by a speech pathologist before feeding is attempted. Once the patient starts oral intake, the Dobhoff feeding tube is removed. Neck drains are removed once drainage is less than 30 mL for a 24-hour period for 2 consecutive days with no air leak. The monitoring skin flap outside the neck is removed at the bedside 5 to 7 days after surgery.
Patients are followed in the clinic at regular intervals after discharge. Bronchoscopy is performed before discharge and at 6-month intervals as clinically indicated. Postoperative radiation therapy can be started 5 to 6 weeks after surgery. The T-tube can be removed 4 to 6 weeks after surgery when the reconstructed airway has healed and airway patency is confirmed by bronchoscopy. Follow-up imaging studies are performed for tumor surveillance and to assess the reconstructed trachea.
COMPLICATIONS
Tracheal reconstruction carries high complication rates. In addition to the medical and systemic complications, surgical complications frequently occur and require careful management.
Air Leak through the Anastomosis
Air leakage is the most common surgical complication and usually occurs during coughing. Most patients have their cricoid cartilage resected, and the flap is sewn to the thyroid cartilage, which is severely calcified in most patients with a very thin mucosal lining. Healing between the skin flap and calcified thyroid cartilage can be delayed. Needle holes through such calcified cartilages can be another source of air leak. Small leaks produce minimal symptoms and are usually detected by subcutaneous emphysema or imaging studies. A catheter placed percutaneously under computed tomographic guidance is adequate for managing minor leaks. The catheter can be connected to a Pleurovac in a manner similar to the management of a pneumothorax. Coverage of the anastomosis with a muscle flap at initial surgery may encourage spontaneous healing of the air leak. Large air leaks may require surgical reexploration and repair and additional muscle coverage.
Exposure of the Supporting Prosthetic Materials
The supporting material is the key to successful tracheal reconstruction. Many materials have been tested, but thus far, there are no ideal materials available to support the soft tissue flap. PTFE grafts are more prone to exposure and infection and therefore should be avoided. Exposure of the supporting material either to the lumen or to the outside skin may require removal of the prosthesis and insertion of a T-tube tracheostomy tube to support the airway. We have not experienced exposure of the Hemashield graft and PolyMax mesh. The PolyMax mesh is widely used for craniofacial surgery. Although the mesh loses strength over time and is resorbed in 12 to 18 months, our experience shows that scarring around the Hemashield graft apparently can prevent airway collapse by the time the mesh is resorbed. This is confirmed in our patients with long-term follow-up up to 4 years both clinically and with imaging studies.
Medical Complications
As with other major surgical procedures, cardiopulmonary and other systemic comorbidities remain major risk factors for postoperative morbidity and mortality after tracheal reconstruction. Therefore, patient selection is of paramount importance for such complex reconstructive endeavors. Severe systemic comorbidities should be considered as contraindications for microsurgical tracheal reconstruction. Obese patients with a thick radial forearm flap also may not be good candidates for such reconstructions because of the inability to maintain a patent lumen because of excessive flap thickness.
Issues with Skin Flap for Lining
Although respiratory epithelial lining is preferred, we have demonstrated that a skin flap lining is not as problematic as once thought. The concern regarding using skin for the tracheal lining stems from the possibility that the shedding of keratin debris into the bronchial tree causes airway irritation and infection. Long-term follow-up of our patients suggests that they tolerate the skin lining well, with no such respiratory symptoms. Bronchoscopy also revealed clean airways, free of debris or secretions. It is likely that a small amount of keratin shedding can be easily cleared by coughing. Our animal studies showed that a buried 6-cm-long, 3-cm-diameter skin tube produced 1 g of keratin and sebaceous debris in 4 weeks. Thus, the hourly production was merely 1.5 μg, which is negligible.
RESULTS
There have been only a few case reports of microsurgical tracheal reconstruction in the literature. Thus far, we have reported the largest series of seven cases with long-term follow-up data. Most of these patients had recurrent thyroid cancer and received external beam radiotherapy after reconstruction. Four patients were decannulated and remained symptom-free at 1.5- to 5-year follow-up. One of these four died from a newly diagnosed cholangiocarcinoma 4 years after tracheal reconstruction, and the other three patients were alive and disease-free at the time of their last follow-up. Follow-up computed tomography (CT) showed stable prostheses and patent airways in all patients. Two patients required permanent tracheostomy because of the need to remove the prosthesis. They retained laryngeal vocal ability despite the need for tracheostomies for airway control.
CONCLUSIONS
Microsurgical tracheal reconstruction may enable selected patients to achieve curative resection of tracheal pathologies and result in a reliable reconstruction with a good quality of life and maintenance of laryngeal function. Future advances in biotissue engineering techniques and tracheal allotransplantation may be future alternatives for extended length tracheal defects.
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