Cervical mediastinoscopy is performed under general anesthesia. The patient is positioned with a roll under the shoulders and between the scapulae, which throws back the shoulders and extends the neck to improve tracheal exposure (Fig. 132-2). The head of the OR table is elevated to 20–30 degrees to decrease venous congestion. The neck and entire chest are draped in the event that a median sternotomy is required to manage a major complication.
A shoulder roll is placed under the shoulders between the scapulae to extend the neck and improve exposure of the trachea.
A 2- to 3-cm incision is made transversely one fingerbreadth (1–2 cm) above the suprasternal notch through skin, subcutaneous tissue, and platysma (Fig. 132-3). The investing layer of deep cervical fascia is identified, and the midline is divided vertically to separate sternohyoid and sternothyroid muscles, which are retracted laterally. The strap muscles also can be divided, but lateral retraction of these muscles usually provides adequate exposure. Deep to the strap muscles and anterior to the trachea, the pretracheal fascia is identified and divided to enter the pretracheal space.
A 2- to 3-cm transverse incision is made in the suprasternal notch (inset). The pretracheal fascia is identified, and the sternohyoid and sternothyroid muscles are divided vertically along the midline.
On the right side of the trachea, the superior vena cava, azygos vein, and tracheobronchial junction form the lateral boundaries of the dissection. On the left, the extent of dissection is limited by the pulmonary artery and aortic arch, with the distal extent of dissection to the left tracheobronchial angle.
An index finger is used to break through pretracheal fascia laterally to gain access to pretracheal and paratracheal lymph nodes (stations 2 and 4) (Fig. 132-4). Inability to break through the pretracheal fascia prevents biopsy of lymph nodes that lie anterior and lateral to the pretracheal fascia. The mediastinoscope is inserted along the superior surface of the trachea (Fig. 132-5). The subcarinal lymph node (station 7) biopsy is performed by using the tip of the cannula to break through the pretracheal fascia distal to the carina. Gentle blunt dissection of nodes is essential to safely separate the lymph nodes from their surrounding structures.
An index finger is used to break through the pretracheal fascia laterally to gain access to station 2 and 4 lymph nodes. (Inset) Blunt finger dissection through the cervical incision.
A. The mediastinoscope is inserted along the trachea. B. The tip of the cannula is used to break the fascia distal to the carina to access the subcarinal lymph nodes (station 7).
Normal lymph nodes usually feel rubbery and may have an anthracotic appearance with gray or bluish black pigmentation. Close proximity of nodes to vascular structures and inflammatory or malignant adhesions places these structures at risk for inadvertent injury and bleeding. Palpation of pulses or visible pulsations are not a good indicator of vascularity because the mediastinum is a small, confined space, and cardiac pulsations are transmitted easily to adjoining structures. Careful, gentle, and thorough dissection of the lymph node usually will confirm its identity. However, if there is any doubt as to whether the structure is a lymph node or a blood vessel, aspiration of tissues prior to biopsy is recommended. A spinal needle (21–22 gauge) on a small syringe can be used for the aspiration. Filling the syringe with a small amount of saline is helpful for detecting small amounts of blood. This technique is especially useful for patients with large, bulky disease, in whom veins such as the superior vena cava, azygos, and innominate are stretched over nodes and are nearly collapsed.
Transpleural mediastinoscopy is useful for investigating mediastinal involvement of bronchogenic carcinoma. Right Pancoast tumors, for example, can be readily assessed using transpleural mediastinoscopy. Through a standard cervical incision, the mediastinoscope is advanced into the right pleural space. In the absence of lung injury, positive-pressure ventilation should prevent the development of pneumothorax, particularly if an end-inspiratory hold is used at the end of the procedure to exclude any residual pneumothorax. The suprasternal notch incision also can be used to access supraclavicular lymph nodes or drain mediastinal cysts.
Subxiphoid mediastinoscopy is performed through a similar-length incision located vertically below the xiphoid process. Once the midline fascia has been incised, a finger can be inserted into the retrosternal space. In patients with scaphoid abdomen, the mediastinoscope can be readily inserted for examination and biopsy.
Bleeding during mediastinoscopy is avoided by gentle dissection of lymph nodes. Judicious use of force and judgment during biopsy of tissue is essential. It is not necessary to harvest the entire lymph node to make a pathologic diagnosis; therefore, lymph node fragments are adequate if the entire lymph node cannot be removed safely. Correctly identifying the lymph node station during the procedure is essential to correctly stage patients. In addition, identification of extracapsular spread or involvement of adjoining mediastinal structures is important to correctly stage patients.
Packing of the mediastinal space controls mild bleeding. Removal of the mediastinoscope after packing is helpful in obtaining hemostasis because this allows the tissues to collapse and obliterate the mediastinal space created by the instrument. Lymph node tissue can be cauterized using the metal-tip cannula. Thermal energy should be used judiciously because it can spread and cause recurrent laryngeal nerve damage and increase the chances of injury to vascular structures. Biopsy of subcarinal lymph nodes is associated occasionally with brisk bleeding from bronchial arteries. This complication is usually managed with packing, as described previously. Occasionally, identified arteries can be clipped with an endoscopic clip applier (EndoClip 5 mm, Autosuture, U.S. Surgical, Norwalk, CT).
After completion of the procedure and securing hemostasis, the incision is closed in layers. The strap muscles are approximated in the midline using 3-0 silk or Vicryl suture. The platysma can be approximated as a separate layer with absorbable suture. The skin is approximated using absorbable subcuticular suture.
Anterior mediastinotomy is performed under general anesthesia. The patient is placed in the supine position. The entire chest is draped in the unlikely event that conversion to median sternotomy is required to control bleeding. The incision classically is made in the second intercostal space on the left side (Fig. 132-6). The incision can be as small as 2 cm in length. The incision is made through the skin and subcutaneous fat, and the pectoral muscle fibers are split to expose underlying intercostal muscles. A small (2-cm) portion of the costal cartilage is excised in the subperichondrial plane. The perichondrium is incised to enter the subperichondrial plane and dissected carefully to avoid injury to the internal mammary vessels and the intercostal vessels and nerve (Fig. 132-7). Alternatively, the intercostal muscles are divided at the superior border of the costal cartilage, the pleura is identified, and the mediastinum is entered without excision of the cartilage. The internal mammary vessels should be safeguarded and retracted laterally or identified and ligated.
A classic 2-cm anterior mediastinotomy incision is made in the second intercostal space on the left side.
A 2-cm portion of the costal cartilage is excised in the subperichondrial plane, and the perichondrium is incised to enter the subperichondrial plane.
The mediastinal pleura is swept laterally, and the mediastinum is entered. The mediastinoscope can be introduced through this incision into the mediastinum to facilitate dissection and biopsy of lymph nodes or masses. Vagus and phrenic nerves course in cephalocaudad direction and must not be injured. The level 6 mediastinal lymph nodes are found at the base of the innominate artery near the course of the phrenic and vagus nerves. The level 5 lymph nodes are closer to the proximal pulmonary artery. The entire dissection typically is performed within the mediastinum. The pleura can be opened to examine the hilum of the lung and to perform wedge biopsy of lung tissue. If the pleura is opened or inadvertently injured, placement of a chest tube is not essential as long as there is no injury to the lung. The pleura may be repaired over a red rubber catheter with positive pressures of 30–40 cm H2O applied to the lung. In the event of lung biopsy or injury to the lung, a chest tube is placed in the pleural space.
After ensuring adequate hemostasis, the incision is closed with reapproximation of the perichondrium with absorbable suture. The pectoralis muscle is reapproximated similarly, and the skin is closed using subcuticular suture. Removal of perichondrium creates a slight, permanent depression on the chest wall after healing. Overall, bleeding from injury to major vascular structures is rare.