Thoracoscopic Approach to Thymectomy with Advice on Patients with Myasthenia Gravis




Introduction



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Thoracoscopy is the application of video imaging technology to standard thoracic surgical procedures. The thoracoscopic approach permits indirect visualization of the thoracic cavity without the necessity of performing a full thoracotomy. Before the current era, the standard surgical approach to thymectomy was through a midline sternotomy or a cervical collar incision. In the last two decades, however, thoracoscopic thymectomy has been used increasingly in selected patients as a means of reducing pain and recovery time while maintaining the quality of gland removal, as well as comparable remission and asymptomatic disease rates compared to other minimally invasive and open techniques.1 Thoracoscopic thymectomy is a good alternative to standard surgical treatment with full sternotomy because it offers excellent visualization (superior to the collar incision) and avoids the morbidity of a sternal division. We enthusiastically advocate a thoracoscopic approach to myasthenia gravis (MG), thymic cysts, thymic masses, and other anterior mediastinal tumors, including small (<2 cm) thymomas.2,3 Bulky thymomas may be better visualized through a standard sternotomy. In this chapter, we describe our technique for thoracoscopic thymectomy with particular advice on ensuring a complete resection.



For the purposes of this description, we will refer to the superior portions of the H-shaped thymus gland as the right or left cervical horns, and the inferior portions will be referred as the right or left lobes.




General Principles



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Thoracoscopic thymectomy is well tolerated by patients of any age or gender owing to the minimally invasive nature of this approach. The usual position for a thoracoscopic procedure is the lateral decubitus position. We have lately added slight cervical flexion to permit caudal migration of the cervical horns and easier dissection, which obviates the need for a cervical incision. This position permits adequate instrumentation of the chest and rapid conversion to open thoracotomy in the event of bleeding or extended re-section. The patient must be intubated with a double-lumen endotracheal tube for split-lung anesthesia to permit selective deflation of the right or left lung. A left-sided double-lumen endotracheal tube is preferred because it is safer and easier to intubate the left mainstem bronchus owing to its length. Most thoracoscopic procedures can be performed with three ports: one for the camera and two for instrument access. It is important to place the ports as far apart from each other as possible to provide opposing angles of access to the intrathoracic target. A camera with a 30-degree angled telescope is also recommended for better intrathoracic visualization. Ports that have been placed too close together prevent adequate countertension on the tissues and cause crowding of instruments. A baseball diamond analogy has been used to describe port placement.4 The camera is at home plate, and the instruments are at first and third base. The target lies between the pitcher’s mound and second base. A fourth port can be added later in the procedure to improve exposure and retraction of the specimen. Blake drain is used unless undue air leak or drainage is noted then a single chest tube is preferred.



In the subset of patients with MG, onset of the disease is correlated with gender and age. MG tends to peak in the second and third decades of life for women versus the sixth and seventh decades for men. For women, early resection is associated with a better response. Thus the typical female patient is a young woman between 25 and 30 years of age who has generalized neuromuscular weakness and is seeking to diminish the consequences of lifelong steroid therapy. Since men experience later onset of disease and a greater incidence of thymoma, male patients usually are older than 55 years of age.




Preoperative Assessment



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Routine preoperative studies include pulmonary function testing, a posteroanterior and lateral chest radiograph, and chest CT scan. The preoperative assessment of patients with MG is performed in collaboration with a team of specialists including the neurologist, anesthesiologist, thoracic surgeon, and pulmonologist. MG is an autoimmune disease resulting from the production of antibodies against the acetylcholine receptors of the neuromuscular synapse. For this reason, patients with severe MG or in crisis may undergo perioperative plasmapheresis or immunoglobulin administration which decreases the level of circulating antibodies.5 Often on long-term steroid therapy, patients with MG also may receive a steroid stress dose before surgery, with subsequent taper in the first postoperative week.




Technique of Thoracoscopic Thymectomy



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Several approaches to thoracoscopic thymectomy have been described, including right, left, bilateral, and bilateral with cervical incision. In general, we prefer to use the right thoracoscopic approach. It provides better visualization of the junction between the innominate vein and the superior vena cava, the so-called innominate–caval junction (ICJ), and thus a better view of the thymic veins. We have encountered more ease of dissection of the cervical horns by adding neck flexion, which permits caudad migration of the lower anterior neck structures. In addition, since the heart and pericardium are predominantly left-sided structures, there is less room on the left for maneuvering the thoracoscope and other surgical instruments.



Right Thoracoscopic Approach


Position


The patient is anesthetized and intubated with a single-lumen endotracheal tube. A flexible bronchoscope is passed through the lumen and down into the airway to assess for the presence of incidental intraluminal lesions or extrinsic compression. If the airway is clear, a double-lumen endotracheal tube is placed for split-lung ventilation, using the flexible bronchoscope to confirm its position. The mechanics of delivering anesthesia in thoracoscopic procedures are detailed in Chapter 5. It warrants mention, however, that muscle relaxants should be used cautiously in patients with MG, if at all, in view of the goal to withdraw the patient from ventilation as quickly as possible after the operation.



For the right thoracoscopic approach, the patient is placed in the left lateral decubitus position. A roll is placed under the patient’s side, elevating the body by approximately 45 to 60 degrees. The easiest way to accomplish this position, we have found, is to place the patient in the full lateral decubitus position and then rotate the patient posteriorly by approximately 30 degrees. The right arm is elevated into a swimmer’s position, and slight cervical flexion is achieved. The right chest is prepped and draped in the usual sterile fashion.



Port Placement


Three portals are created in a triangular configuration (Fig. 159-1). The first port (5–20 mm) is placed over the fifth intercostal space (ICS) between the anterior axillary and midaxillary lines. From this location, the chest tube exits the skin anterior to the superior iliac crest of the pelvis, thus preventing chest tube compression or kinking in the postoperative period. This port site is one ICS above the site that we generally use for thoracoscopic procedures of the posterior or midchest (i.e., sixth ICS) and permits use of the curved or straight Foerster (ring-hatched) forceps in the upper anterior mediastinum. The second port (5 mm) is placed in the fifth ICS between the mid- and posterior axillary lines, near the tip of the scapula. The third port (2 cm) is placed at the base of the axilla over the top of the third rib. The size of the ports may vary depending on surgical instrumentation and surgeon preference.




Figure 159-1


For right thoracoscopic thymectomy, the patient is in the left lateral decubitus position and elevated approximately 30 degrees by placing a roll under the patient’s side. Three ports are placed in triangular configuration with the patient’s arms in swimmer’s position.





The camera is placed initially in the anterior fifth ICS port for exploration of the chest. We recommend a 30-degree 5-mm telescopic lens for easy visualization and dissection of the mediastinum. Ventilation is stopped on the right side. The entire thoracic cavity is examined to identify the surgical landmarks, namely, thymus gland, phrenic nerve, superior vena cava, and internal mammary vessels (Fig. 159-2). The posterior diaphragmatic sulcus is examined for “drop metastases.”




Figure 159-2


Important mediastinal landmarks that are visible with the camera placed in the anterior fifth intercostal port.





The camera is moved to the posterior fifth ICS port (5 mm) for the thymic dissection. This produces the classic dissection triangle with the surgeon standing posterior to the patient (Fig. 159-3). The left-hand instruments enter the axillary port, the right-hand instruments enter the anterior fifth ICS port, and the camera eye is between the left and right hands in the posterior fifth ICS port. A fourth port can be created at the surgeon’s option and, if so, usually is placed caudally and later in the procedure to aid in dissection of the contralateral side. Placement is based on anatomic considerations, but a fourth port is often located in the seventh ICS in the midaxillary line.

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Dec 30, 2018 | Posted by in VASCULAR SURGERY | Comments Off on Thoracoscopic Approach to Thymectomy with Advice on Patients with Myasthenia Gravis
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