The mediastinal pleura is divided circumferentially around the hilum using either scissors or an energy probe, including the inferior pulmonary ligament. Harvesting the lymph nodes in the aortopulmonary window gives better exposure to the proximal pulmonary artery. This must be done carefully to avoid injuring the recurrent laryngeal nerve, which branches off the vagus nerve on the inferior surface of the aortic arch and then dives into the mediastinum immediately inferior and adherent to the arch. Unless it is involved with tumor, the phrenic nerve should also be preserved until a decision is made about sleeve resection. It may abut the anterior aspect of the nodes in the AP window, and so is also at risk.
Harvesting the subcarinal lymph nodes gives better access to the bronchus and allows the surgeon to better palpate the bronchus. Cautery should be used judiciously or not at all in this space, since the blood vessels to the bronchus arise here.
The vagus superior to the aorta or the recurrent nerve can be harvested if either is involved with cancer. However, resection of these nerves will lead to vocal cord paralysis.
Evaluation for Sleeve Resection
The lung is examined carefully to determine whether sleeve resection is possible. Maneuvers that help include:
Dividing the pleura circumferentially;
Taking down the inferior pulmonary ligament;
Complete parenchymal separation of the upper and lower lobes; and
Completing the mediastinal lymphadenectomy.
Factors that make sleeve resection difficult include:
Tumors that invade the pericardium at either pulmonary vein;
Tumors that involve both the main pulmonary artery and the left mainstem bronchus; and
Tumors that involve artery or bronchus but extend into the fissure to involve the other lobe. Thus, upper lobe tumors that extend inferiorly to involve the fissure extensively or lower lobe tumors that extend superiorly can be difficult to resect and reconstruct.
The pulmonary artery is dissected away from the vein anteroinferiorly and the bronchus posteriorly (Fig. 72-1). This dissection is made safer by proceeding posteriorly to separate the artery from the bronchus (Fig. 72-2). Quite often this can be done bluntly, either with Kittner dissectors or with an index finger (see Fig. 72-1), and usually can be done before mobilizing or dividing the superior vein. However, in patients with an inferiorly positioned artery or superiorly positioned vein, the vein can be dissected and divided first.
Left pneumonectomy. Using a combination of blunt and scissors dissection, the pulmonary artery is dissected away from the pulmonary vein anteroinferiorly.
The bronchus is dissected away from the pulmonary artery posteriorly.
The artery should be occluded with either a vascular clamp, a tourniquet, or a vascular stapler (closed but not fired) for 2 to 3 minutes to ensure that right ventricular failure or pulmonary hypertension will not result after pneumonectomy. After the artery is clamped, systolic blood pressure and oxygenation are assessed, and if stable, indicate that the patient can tolerate pneumonectomy. If hemodynamic instability or hypoxia develops, a pulmonary artery catheter may be inserted to direct pressor treatment, but in most cases, it is necessary to perform a sleeve resection or abandon the procedure altogether. Care should be taken during this maneuver not to “fracture” the PA when temporarily occluding the vessel.
Additional length on the artery (to allow complete resection) can be obtained by two specific maneuvers:
Dividing the ligamentum arteriosum (being careful to avoid injury to the recurrent nerve).
Opening the pericardium to identify the very short left main pulmonary artery within the pericardium. In this maneuver, it is recommended (obligatory) to test clamp the artery before it is divided because the anatomy may be distorted by the malignancy, which can lead to inadvertent division of the main pulmonary artery.
The artery is divided by one of several techniques: vascular stapler (two fires with division between two stapler lines or with an endostapler that cuts between two stapler lines); vascular clamps proximal and distal, with a double suture line of 5-0 Prolene; or some combination of the above techniques (Fig. 72-3).
A vascular stapler is used to divide the artery. Other techniques may be used, including proximal and distal vascular clamps oversewn with a double suture of 5-0 Prolene.
The pulmonary veins are now divided. If the tumor invades the pericardium, or if the pericardium has been opened to gain arterial control, the veins can be controlled and divided by extending the pericardial opening inferiorly, just posterior to the phrenic nerve. (The pericardium should be reconstructed if it is opened.) The pulmonary veins form a single branch as they enter the left atrium and can be divided at this level with any of the techniques described for the artery. Blue (3.5 mm) staplers, rather than vascular-load staplers, should be used to control the atrium because vascular loads can fail on this thicker tissue (Fig. 72-4) (Table 72-3).
The pulmonary veins are divided. If the pericardium has been opened to gain control of the tumor, this incision can be extended to control the pulmonary veins (inset).
Table 72-3Stapler Types and Size ||Download (.pdf) Table 72-3Stapler Types and Size
Vascular staplers, gray, white or red, usually with a 2.5-mm gap. These are used to close pulmonary artery or single pulmonary veins
Medium thickness staplers, blue, usually with a 3.5-mm gap. These are used to divide parenchyma or to divide the atrium
Heavy thickness staplers, green, usually with a 4.8-mm gap. These are used for thick pulmonary parenchyma or for bronchi
Table 72-4Bronchial Stump Care ||Download (.pdf) Table 72-4Bronchial Stump Care
Avoid removal of bronchial adventitia
Divide the left bronchus within the aortopulmonary window to yield a short stump
Harvesting the subcarinal nodes is important, but use clips or scissors rather than cautery or energy, which increase the chances of devascularization
The stump should be closed from an anterior-to-posterior direction, such that the flexible membranous bronchus can move against and seal the more rigid cartilaginous bronchus
The bronchus should be covered with vascularized tissue, either pericardium or pericardial fat pad/thymus
When dividing the veins outside the pericardium, the superior and inferior veins must be identified separately. The inferior vein begins at the superior edge of the inferior pulmonary ligament, and the superior vein is the most anterior structure of the hilum. These veins can be divided with vascular stapler loads or controlled with vascular clamps and oversewn with 4-0 or 5-0 Prolene.
Careful management of the bronchus decreases the chance of bronchial stump leak with its attendant dangers (Table 72-4). The table lists aspects of dissection that can affect the chances of bronchial stump devitalization or devascularization.
The bronchus is usually the last structure divided (Fig. 72-5). The lung is grasped and used to deliver the bronchus inferiorly into the chest, with the goal of dividing the left main bronchus just distal to the carina, while leaving sufficient length to avoid tension on the closure. The anesthesiologist is asked to hold ventilation and to back out the double-lumen tube or blocker used to collapse the left lung. The bronchial clamp or bronchial stapler is positioned across the bronchus to close it in an anterior-to-posterior fashion. If a stapler is used, the heavy load (green) or 4.8-mm stapler is chosen. The bronchus is divided and closed with the stapler or with absorbable suture (typically 2-0 or 3-0 PDS or Vicryl). This can be facilitated by dissection of the subcarinal lymph node packet.
A. Before dividing the bronchus, the lung is grasped to deliver the bronchus inferiorly into the chest. B. The bronchial clamp or stapler is positioned to close the bronchus in an anterior-to-posterior fashion. C. The bronchus is covered with a pericardial fat pad or thymus and sutured either to the bronchus itself or to the surrounding tissues.
The bronchus must be tested to 30 cm H2O. If no leak is seen, the bronchus is covered with vascularized tissue. I prefer to use pericardial fat pad or thymus, but vascularized pericardium can be used. Others describe using intercostal muscle. It should be sutured either to the bronchus, itself, or to the tissues around the bronchus.
Patients undergoing right pneumonectomy are more likely to die from this procedure than left pneumonectomy patients. Mortality typically is due to the complications of recovering from surgery rather than the surgery itself. Consequently, for right pneumonectomy, postoperative management is crucial.
As on the left side, I perform thoracoscopy to identify any occult pleural metastases. If no metastases are seen, the appropriate incision is selected and the chest opened. The pleura around the hilum is divided and the inferior pulmonary ligament is taken down (Fig. 72-6). For lesions in the hilum, dividing the azygos vein and harvesting the right paratracheal nodes first gives better exposure to the proximal pulmonary artery and proximal right mainstem bronchus.
Right pneumonectomy. The pleura surrounding the hilum is divided, the inferior pulmonary ligament is taken down, and for tumors in the hilum, the azygos vein is divided, harvesting the right paratracheal nodes first (inset).
As for left pneumonectomy, the tumor and lung should be evaluated to determine whether sleeve resection, rather than pneumonectomy, can be done. The right upper lobe sleeve is the most straightforward sleeve resection to perform—both the airway and the artery can be sleeved.
Once the decision to proceed to pneumonectomy is made, the artery is dissected away from the bronchus and vein. A patient who has had previous chemoradiation therapy or who has a history of granulomatous disease in the mediastinal lymph nodes often will have dense scarring between the posterior arterial plane and the anterior plane of the bronchus. For this situation, proximal control of the artery is needed.
Several maneuvers permit proximal control of the right main pulmonary artery. The first and simplest is to divide the azygos vein and perform a right paratracheal node dissection. For tumors with more extensive involvement of the mediastinum, the proximal pulmonary artery can be approached by opening the pericardium (Fig. 72-7). If more room is needed, the pulmonary artery can be identified medial to the superior vena cava, since the right main pulmonary artery is very long. The right pulmonary artery can be divided just after its bifurcation (this is often found to the left of the patient's midline), and the artery is then delivered back to the right hemithorax posterior (or underneath) the superior vena cava. This approach markedly diminishes the chance of hemorrhage.
When there is extensive mediastinal involvement, the proximal pulmonary artery can be approached medially to the superior vena cava.
Pericardiectomy and Reconstruction
Some textbooks state that pericardial reconstruction after resection must be done on the right side to prevent cardiac torsion on the axis defined by the superior and inferior vena cavae, but it is not necessary to do so on the left side. I have had patients arrest after left-sided pericardiectomy without reconstruction and believe that the extent of resection, rather than the side, is the important factor.
The only goal for reconstruction is to fill the pericardial defect in such a manner as to prevent cardiac herniation. For limited resections (<2 cm in diameter), reconstruction may not be necessary to prevent herniation, but probably is helpful to avoid cardiac irritation and supraventricular tachyarrhythmias. Larger defects sometimes can be filled with the vascularized flap used to buttress the bronchus, especially if a bulky pericardial fat pad is used.
Most surgeons use a nonabsorbable material – PROLENE (Ethicon, Inc., Somerville, NJ) or Gore-Tex® (W.L. Gore and Associates, Flagstaff, AZ) mesh – to reconstruct the pericardium (Fig. 72-8). These patches should be sewn into place using interrupted sutures placed approximately 1 cm or more apart since the goal is to anchor the patch in place but not to make it watertight. The patch should also be loose to avoid constricting the heart, which will assume a different shape and position when the patient is upright. The patch should be loose to the point of being floppy, with special attention to avoid constriction of the superior vena cava. Finally, limited experience indicates that absorbable material, such as Vicryl mesh, can be used to reconstruct pericardial defects.
The pericardium is reconstructed with nonabsorbable PROLENE or Gore-Tex® mesh. The patch is sewn in place with interrupted sutures approximately 1 cm or more apart. The patch should be extremely loosely fitted to the point that it can be described as being floppy.