72: Pneumonectomy

As long as surgery remains the best curative treatment for lung cancer, patients will continue to require pneumonectomy to treat lung cancer and for other occasional problems.¹ Arguably, no other surgery carries as high a risk for perioperative mortality as pneumonectomy. Operative mortality from pneumonectomy has been reported to be between 5% and 20%.^2–8 In a meta-analysis of 27 studies, 90-day mortality for right pneumonectomy was 20% and left pneumonectomy was 9%, for an overall mortality of 11%.⁹ For this reason, appropriate selection, operative technique, and postoperative management of patients who potentially may undergo pneumonectomy is crucial. We say potentially because patients scheduled for pneumonectomy ultimately may undergo a sleeve resection or exploration without resection depending on the findings at surgery.

Surprisingly, low preoperative lung function has not been demonstrated consistently to increase the perioperative risk of pneumonectomy, although some authors have found preoperative lung function to be an important factor.^10–12 This finding may result from diligent efforts to identify and eliminate patients with poor pulmonary function from the surgical pool. Some have found poor preoperative lung function to increase the preoperative risk.^13–15 Other factors have included increased age,^{7,8,11,14,16,17} right-sided procedures,^{8,9,12,14–19} preoperative chemo/radiation,^12,14,20 large intraoperative fluid volumes,^12,20,21 perioperative cardiac dysrhythmias,¹⁶ and immediate preoperative smoking history.^12,22

This chapter includes discussion of the preoperative evaluation and management of pneumonectomy patients, the decision to perform pneumonectomy rather than sleeve resection, the technical aspects of the operation, and the postoperative management, all with the goal of decreasing perioperative mortality.

Staging, Surgical, or PET?

All patients with lung cancer, especially those who may undergo pneumonectomy, should first undergo preoperative staging (Table 72-1). At this time, a complete history and a physical examination that focuses on the identification of lymph nodes and liver masses, followed by a chest CT scan and a PET scan, are appropriate. This evaluation will rule out distant metastases other than brain metastases. Patients without symptoms of headache and with PET-negative mediastinum are unlikely to have brain metastases, so that brain CT scans or MRIs are not obligatory. However, the risk of the procedure supports appropriate evaluation to rule out brain metastases if the surgeon desires.

Candidates for pneumonectomy typically have large or hilar masses and thus a high likelihood of mediastinal metastases. Although PET scans are quite sensitive for detecting mediastinal metastases, they remain less accurate than mediastinoscopy²³ (see Chapter 70). For this reason, tissue biopsy (either with endobronchial ultrasound, preoperative mediastinoscopy, or thoracoscopy) is indicated for patients who may undergo pneumonectomy, even if they have a PET-negative mediastinum. PET scans are useful for ruling out distant metastases, but should not be the only study used to evaluate the mediastinum.

Surgical Evaluation

We have discussed the importance of surgical staging of the mediastinum prior to pneumonectomy. Two other surgical evaluations (bronchoscopic and thoracoscopic) should be considered.

Bronchoscopic evaluation of the airway will ensure that a patient with a hilar mass on the right does not also have an endobronchial lesion on the left. The patient could die from the surgery to attempt to cure his right-sided cancer, and even if the surgery is successful, the pneumonectomy would have no impact on the left-sided cancer.

Thoracoscopic examination and staging of the pleural space benefits patients undergoing pneumonectomy in several ways²⁴:

1. Thoracoscopy helps to rule out pleural metastases that usually cannot be identified except at exploration.

2. Thoracoscopic nodal sampling or lymphadenectomy can evaluate suspicious nodes in patients who have not had tissue nodal sampling.

3. Thoracoscopy can be used to determine the incision used for resection (see also Chapters 2 and 70).

Cardiopulmonary Evaluation

An extensive but complicated literature describes the various modalities used to evaluate preoperative lung function as a means to predict postoperative complications. A preoperative forced expiratory volume in 1 second (FEV₁) of more than 2 L has been relatively arbitrarily chosen as a threshold for resection without further pulmonary evaluation and has been confirmed by experience.

The obstructive nature of cancers that may lead to pneumonectomy assures that many patients will have less than 50% perfusion to the affected lung. Quantitative perfusion scanning has been used successfully for almost 30 years to determine the relative contribution of each lung to the patient's lung function.⁶ Patients with a predicted postoperative FEV₁ (better than preoperative FEV₁) of more than 800 mL are considered to have adequate pulmonary reserve to undergo resection. This technique has been found to be accurate in long-term follow-up (up to 5 years),²⁵ especially with respect to predicting the postoperative FEV₁²⁶ (Table 72-2). Kim et al.¹³ have reported that perfusion less than 35% to the resected lung diminishes the operative risk. These parameters are also currently used in most cooperative group trials including lung resection.

Typical cardiac ischemia evaluations (i.e., stress testing) should be done in all patients with any history of cardiac ischemia (angina, other chest pain, or history of coronary artery bypass) and should be considered in patients with significant peripheral vascular disease.

Left Lung Resection

Left pneumonectomy generally is safer than right pneumonectomy, at least in terms of overall perioperative and postoperative mortality. On the other hand, risks associated with long bronchial stump require careful technical attention to details of resection. However, the procedure may be technically more difficult, especially in patients with large hilar masses.

Left hilar cancers are truly in “tiger country,” approaching or involving the aortic arch, recurrent laryngeal nerve, phrenic nerve, pericardium, and the main pulmonary artery before it bifurcates into right and left main pulmonary arteries. (The left main pulmonary artery is very short.) The primary procedures are described separately, since the anatomy and the dissections are different on the left and right sides.

Left Pneumonectomy

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:

1. Dividing the pleura circumferentially;

2. Taking down the inferior pulmonary ligament;

3. Complete parenchymal separation of the upper and lower lobes; and

4. Completing the mediastinal lymphadenectomy.

Factors that make sleeve resection difficult include:

1. Tumors that invade the pericardium at either pulmonary vein;

2. Tumors that involve both the main pulmonary artery and the left mainstem bronchus; and

3. 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.

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:

1. Dividing the ligamentum arteriosum (being careful to avoid injury to the recurrent nerve).

2. 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).

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).

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.

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.

Right Pneumonectomy

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.

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.

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.

There is insufficient space to discuss every aspect of the perioperative management for lung resections. However, fluid management is a key problem that deserves attention and can prevent complications in patients undergoing pneumonectomy. Several studies have been published indicating that excessive fluid given during the perioperative period can lead to increased postoperative mortality. Nevertheless, in the immediate perioperative period, 2 to 5 L of fluid will accumulate in the chest. This amount must be added to the patient's basic needs for fluid. Renal function laboratory values (blood urea nitrogen [BUN] and creatinine) can be used to guide fluid resuscitation, as can urine output. Perhaps the main caveat for these patients is that they do not develop the third-space accumulation that laparotomy or cardiac patients do and therefore should be either run relatively dry (approximately 80% of predicted needs) or at euvolemia.

The high risk of pneumonectomy underscores the importance of proper preparation and experience in both the conduct of the surgery and the perioperative management. Review of the idiosyncrasies of the pulmonary anatomy and other common pitfalls is warranted.

I have used endoscopic vascular staplers for all pneumonectomies. The reticulation and angulation of the current staplers allow for safe division of the main PA. It is particularly helpful when there is limited space within the pleural cavity to maneuver or when an intrapericardial pneumonectomy is done. An important technical consideration is the liberal use of intrapericardial dissection, especially with left-sided pneumonectomies; we never hesitate to get better proximal control of bulky tumors both for division of the PA and PV. Likewise, in general, the vein is divided first as it allows a safe approach to the PA. In contrast, this often results in “trapping” of a large volume of blood in the lung and also may make the lung difficult to rotate once it had become engorged. In patients undergoing pneumonectomy after neoadjuvant chemoradiation, we routinely use muscle flaps, including the intercostal as well as the serratus anterior muscles. This is helpful especially after pneumonectomy as it helps fill the space as well as buttressing the bronchial stumps.