TSRA Content:
Author: Jack Haney, MD
Revision of this chapter that is originally written by Jack Haney, MD
Preoperative Evaluation
Pneumonectomy may be indicated in patients with central tumors or tumors in multiple lobes, depending on the patient's medical status. Parenchymal-sparing resections (ex. sleeve lobectomy), if possible, are generally preferred over pneumonectomy as long as adequate margins can be obtained. Nevertheless, preparations for pneumonectomy should generally be made in any case where it is a possibility.
Beyond imaging, workup should include spirometry, V/Q scan, and cardiac evaluation. An FEV1 of greater than 2 liters predicts tolerance of pneumonectomy with low complication rate, though quantitative V/Q scanning in conjunction with spirometry more reliably helps predict postoperative pulmonary function. Obtaining pulmonary function test, with DLCO, is essential in patients with prior lung disease (i.e., emphysema, COPD, etc.) Predicted postoperative FEV1 of <40% predicted or 800 mL precludes pneumonectomy.
Following pneumonectomy, the entire cardiac output is rerouted through one lung, which may result in a significant elevation in pulmonary artery pressures and right ventricular strain. A stress echocardiogram, followed by cardiac catheterization, if necessary, is standard at our institution to evaluate for ischemic heart disease and pulmonary hypertension.
Anesthesia Considerations
The preparation of a patient for pneumonectomy resembles that for lobectomy, with the usual addition of a central venous line on the ipsilateral side of the resection to be performed.
This is a very crucial step in anesthesia management and that surgery cannot be offered to a patient who is expected to become ventilator dependent, postoperatively. Hence, it is very important to have an objective preoperative assessment for risk stratification
Conduct of Operation
Pneumonectomy can be done via thoracotomy, sternotomy, or thoracoscopic incisions. Most frequently a posterolateral thoracotomy is employed. The inferior pulmonary ligament is released to the level of the inferior pulmonary vein and the pleura overlying the hilum is incised medially and laterally. Medially, it is important to identify the phrenic nerve on the pericardium and preserve it, if possible, even though the lung is removed. Over time a paralyzed hemidiaphragm will lead to significant paradoxical motion during respiration and thereby limit pulmonary reserve. Both inferior and superior veins are isolated. Frequently a large hilar N1 node behind the superior vein is dissected into the specimen. The main pulmonary artery is then carefully encircled. For bulky tumors, it may be necessary to enter the pericardium to achieve a negative margin, although intrapericardial dissection increases the risk of postoperative atrial arrhythmia and cardiac herniation.
On the left side, the pulmonary artery is shorter and tethered at the ligamentum arteriosum. This may be divided but is usually not necessary and should be avoided if possible due to the proximity of the left recurrent nerve, which loops around the aorta at this level. If there is a concern about pulmonary arterial hypertension, one may test clamp the pulmonary artery and assess the hemodynamic response. If hemodynamics deteriorate (elevated pulmonary pressures, decreased systemic pressures), pulmonary vasodilators such as nitric oxide should be initiated. Once the decision is made for resection, the superior and inferior pulmonary veins are divided. The pulmonary artery is then divided.
The origin of the mainstem bronchus is then exposed, dissection of which is facilitated by removal of the subcarinal (level 7) nodes. The right mainstem bronchus is shorter but easier to expose, as the left mainstem bronchus runs beneath the aortic arch. On the right, the azygous vein may be divided to facilitate exposure. Retraction of the lung inferiorly extends the bronchus. The bronchus should be divided flush against the carina after ensuring that any suction catheters are removed from the airway and that the endotracheal tube moves freely following stapler closure. The bronchial margin should undergo a frozen section evaluation to confirm an adequate resection. Manually removing the staples from the specimen-side of the bronchus is a simple way to gain an additional 3mm of margin. If the margin is positive, the bronchial stump should be inspected and divided more proximally. If necessary, a carinal pneumonectomy may be performed, which involves reanastomosis of the contralateral mainstem bronchus to the trachea above the resected carina.
Once the pneumonectomy is completed, coverage of the bronchial stump must be considered. This is more important on the right because the stump on the left retracts into the mediastinum beneath the aortic arch and thus has a lower chance of developing a bronchopleural fistula. Although some surgeons prefer to cover the bronchial stump routinely, others cover it selectively in cases of infection, prior irradiation, and/or reoperation. Coverage may be achieved by using the intercostal muscle flap, pericardial fat pad, or divided azygous vein. If pericardial resection was required, one must consider reconstruction. This is always required on the light, which incurs a greater risk of cardiac herniation.
Postoperative Care
Management of the post-pneumonectomy space is surgeon specific. Some routinely place a chest tube, reasoning that drainage provides information about postoperative bleeding and equalizes intrathoracic pressures. A special pleurovac ("balanced pneumonectomy drainage") used in this situation prevents excessive positive or negative pressure from developing within the space and has been shown to decrease the risk of postpneumonectomy pulmonary edema If fluid is detected, in addition to evacuation of the fluid, intrathoracic pressure monitoring serve as a guide for fluid extraction and decrease any cardiopulmonary risks especially if extraction the fluid rapidly.
If this is unavailable and a standard pleurovac is used, one should remember that no suction should be applied, as this negative pressure may cause cardiac herniation. Others aspirate air from the pneumonectomy side after returning the patient to supine position to allow the mediastinum to shift back toward the midline. Others aspirate the chest only after an initial postoperative film assesses the position of the heart, to restore it to n1idline as needed. Any of these strategies may be justified; it has been our postpneumonectomy routine to leave a chest tube and remove it after 24 hours.
Postoperative management requires one to respect the limited remaining lung capacity, as aspiration, pneumonia and edema can be fatal. We typically keep patients NPO until POD#1 and obtain a clinical swallow exam if there is hoarseness or any other indication that they are at risk of aspiration. There are also several complications specific to pneumonectomy that one must consider. Cardiac herniation through a pericardial defect may cause acute torsion of the heart and hemodynamic collapse. This1nay be precipitated by changes in patient position, or by the application of suction to the chest tube. If suspected, the patient should be immediately turned laterally with the remaining lung on the dependent side and any suction on the pleural drainage device discontinued. Reoperation to patch the pericardial defect is required.
Postpneumonectomy pulmonary edema is a potentially fatal complication that can develop in the remaining lung, as a result of increased hydrostatic pressure within the remaining pulmonary vasculature and impairment of lymphatic drainage due to the division of shared lymphatic channels between the lungs. Ede1na is more common following right pneumonectomy because of its larger size. It is critical to avoid iatrogenic fluid overload, usually keeping volume resuscitation below 101nL/kg intraoperatively and 1.5 L within the first 24hrs postoperatively. Crystalloids are generally favored for fluid replacement as complex carbohydrate colloids may worsen the severity of edema since they cannot be reabsorbed from the lung as quickly. A side of caution must be established when considering any blood product transfusion as this will affect respiratory function, especially tidal volume
Bronchopleural fistula (BPF) is a devastating early or late complication. Predisposing factors include infection (usually around POD 8-12), preoperative irradiation, and prolonged postoperative mechanical ventilation. Radiographic features suggestive of fistula include progressive pneumothorax or subcutaneous emphysema and shift of the mediastinum away from the postpneumonectomy space. Late BPF may present with signs and symptoms of infection as the postpneumonectomy space is soiled with airway organisms, or radiographically with a falling air-fluid level on that side. Evaluation of BPF is through bronchoscopy, which may reveal a frank dehiscence or more commonly, bubbling or liquid arising from the previously closed bronchial stump. Management is usually aggressive; for early presentations, patients often require urgent reoperation and coverage of the bronchial stump with vascularized tissue. For late presentations associated with empyema, urgent drainage of the pleural space, control of infection, nutritional optimization, and delayed reoperation to provide coverage to the stump are indicated., Empyema may accompany, but is not always associated with, BPF. Patients show clinical and laboratory signs of infection, although it can also be presented in the absence of infection. Radiographic features include rapid filling of a postpneumonectomy space (early empyema) or mediastinal shift away from the postpneumonectomy cavity. Treatment requires aggressive antibiotics and drainage, occasionally with obliteration of the pleural cavity or open thoracostomy (Eloesser flap).
Postpneumonectomy syndrome is a delayed complication seen well after surgery. It causes increased dyspnea and recurrent infection and occurs when overexpansion of the remaining lung displaces the mediastinum into the empty hemithorax and results in torsion of the remaining mainstem bronchus. Treatment requires reoperation and placement of prostheses in the resection bed to restore mediastinal anatomy.