Extrapleural Pneumonectomy

Timothy E. Miller

Case Vignette

Extrapleural pneumonectomy (EPP) was introduced in the 1940s for the treatment of tuberculous empyema and other pleural space infections.¹ It is a radical surgery that differs from conventional pneumonectomy in that the lung is removed en bloc, together with parietal and visceral pleura, ipsilateral hemidiaphragm and pericardium, as well as mediastinal lymph nodes. In modern times the operation is reserved almost exclusively for the treatment of malignant pleural mesothelioma (MPM). Rarely, it can also be performed for locally advanced lung cancer, or other malignancies and infections confined to a single pleural space.

EPP is a technically difficult operation accompanied by a significant mortality rate, recently estimated at between 3% and 7%.^2–4 This has dramatically improved since the 1970s when mortality was over 30%,⁵ with the trend now toward improved operative survival, especially if used as part of a multimodal approach (Table 14–1). Nevertheless, morbidity remains high even in large volume centers with aggressive intervention, exceeding that for pneumonectomy.⁴ Accordingly its use remains controversial, and patient selection is imperative. Anesthesia management is challenging and may contribute to safe patient outcomes.

Table 14–1. Mortality of Extrapleural Pneumonectomy

MALIGNANT PLEURAL MESOTHELIOMA

Malignant pleural mesothelioma (MPM) is a rare, locally aggressive tumor of the mesothelial cells that line the pleura. It tends to spread or recur locally, and encases and invades the lung parenchyma in late stages of the disease. MPM is almost universally caused by, and in fact owes its entire existence as a disease entity to its relationship with asbestos. Asbestos is a naturally occurring mineral found all over the world but mainly in Canada, South Africa, Australia, and northern Italy. Due to its extraordinary fire-resistant properties it was used in the construction and shipping industries in the 1940s, during which time an estimated 40% of the US workforce were exposed.⁶ The first description of an association between MPM and asbestos exposure was by Wagner in patients exposed to the long, fine asbestos fiber crocidolite in South African mines.⁷ All types of asbestos fiber can cause mesothelioma, with crocidolite considered the highest risk. When inhaled, the fibers are too large to be removed by pulmonary macrophages, and over the years they burrow into the serosal surfaces of the pleura, pericardium, and peritoneum. Fortunately only 2% to 10% of individuals with prolonged asbestos exposure will develop MPM, whereas over 80% of MPM patients have a history of exposure to asbestos.⁸

The average latency period following exposure and development of the disease or death is very long—usually a minimum of 20 years—although the range is wide. Cases developing within 15 years of exposure are rare. This is unlike most risk factors, including smoking, when increasing time from stopping exposure to the carcinogen will decrease the risk of malignancy. In 1972, the US Occupational Safety and Health Administration established permissible exposure limits to asbestos, and since then many countries have banned its use completely. The importance and relevance of the latency period is reflected by the increasing incidence of mesothelioma. In the US the current incidence is 3000 cases per year, comprising about 3% of cancer diagnoses, and this is projected to increase until at least 2020.⁹

Typically, patients with MPM present with a pleural effusion, which is often associated with chest wall pain or breathlessness. The chest pain typically progresses relentlessly during the course of the illness. Constitutional symptoms such as weight loss and fatigue can be present, and are often associated with a poor prognosis. Occasionally the disease is found incidentally on a chest x-ray (Figure 14–1). CT scans often demonstrate encasement of the lung by a thickened pleural peel (Figure 14–2).

Figure 14–1. Chest radiograph demonstrating the four classic findings of a patient with the clinical diagnosis of pleural mesothelioma: pleural thickening, pleural effusion, decreased thoracic volume, and no shift of the mediastinum to the affected side.

Figure 14–2. Pleural thickening in a 51-year-old man with MPM. Axial contrast-enhanced CT scan shows circumferential and nodular left-sided pleural thickening (arrows). The tumor encases the contracted left hemithorax, having a rind-like appearance.

Diagnosis of MPM is possible from cytological examination of pleural fluid, but findings are often negative despite repeated sampling. The gold standard is thoracoscopy, which yields a diagnosis in 98% of patients.¹⁰

Treatment

Without treatment, MPM is associated with an extremely poor prognosis: a median survival duration of less than 1 year and a 5-year survival rate of less than or equal to 1%.¹¹ No single treatment modality dramatically improves this since none reliably results in cure.

The goal of any surgical treatment is complete resection. However, in the case of MPM this is rarely achieved—presumably due to the diffuse spread of MPM throughout the hemithorax, and the difficulty of achieving deep margins. Therefore, treatment has focused on surgery in combination with a multimodality treatment program. Other therapies include systemic or intrapleural chemotherapy, high-dose hemithoracic radiation, and intensity-modulated radiation therapy (IMRT).¹²

The two main surgical options are EPP and pleurectomy/decortication (P/D), which involves resection of the pleura, pericardium and diaphragm when necessary but spares the lung. There are no randomized controlled trials between these techniques, and no established practice guidelines. EPP offers the most complete cytoreduction, and is considered by many to be the best surgical option. However, a recent multicenter retrospective series showed improved 5-year survival after P/D.¹³ Previous series have argued against this perspective,^14–16 with Sugarbaker et al finding a median survival of 51 months in selected patients after EPP.¹⁵ The decision to perform P/D is often made intraoperatively, with early disease commonly resected by P/D when it appears macroscopic complete resection can be achieved. Bulky disease is more likely to be approached by EPP, offering significant bias to any comparative retrospective series. An additional benefit of EPP is that it facilitates the administration of postoperative hemithoracic radiation, which is not possible after P/D, and provides excellent local disease control.¹⁷

The recent mesothelioma and radical surgery (MARS) trial is the first randomized controlled trial to compare EPP versus no EPP in the context of trimodal therapy (chemotherapy, radiotherapy, and further surgery if needed). Although the trial was small with only 50 patients randomized, patients undergoing EPP had shorter median survival (14.4 months vs 19.5 months), and more serious adverse events (10 vs 2), without any gain in quality of life. The authors therefore conclude that EPP within trimodal therapy may offer no benefit, and possibly harm patients. This is almost certain to significantly decrease the number of EPPs performed in the coming years. Further studies are needed to evaluate the role of lung sparing surgery in the future management of mesothelioma.¹⁸

TECHNIQUE OF EXTRAPLEURAL PNEUMONECTOMY

Step One: Incision

The extrapleural space is usually approached through an extended posterolateral thoracotomy incision in the sixth intercostal space with resection of the sixth rib, although a median sternotomy can be used for a right EPP.

Step Two: Extrapleural Dissection

Combined blunt and sharp extrapleural dissection is performed superiorly toward the apex of the thorax, and then medially down to the azygos vein. Packing the dissected area diminishes blood loss from the numerous small vessels lining the inner thoracic cavity. During this dissection, any internal mammary grafts on the operative side will almost certainly be lost, and there may be traction to the superior vena cava (SVC). Inferiorly the diaphragm is divided and dissected from the underlying peritoneum, taking care to keep the peritoneum intact and prevent peritoneal seeding.

Step Three: Division of the Major Vessels and Bronchus

The pericardium is opened and resected, with the major vessels dissected free. The main pulmonary artery and veins are divided using a vascular stapler. After a complete subcarinal lymph node dissection the main stem bronchus is exposed and divided (Figure 14–3). This can be performed under direct vision with a fiberoptic bronchoscope to assure a short stump that is flush with the carina.¹⁹ The specimen is then removed en bloc, followed by radical mediastinal lymph node dissection.

Figure 14–3. A. The intrapericardial dissection and isolation of the hilar vessels with subsequent ligation and division of the vessels using endoscopic vascular staplers. B. Operative drawing after completion of the pericardial and diaphragmatic reconstruction. The right bronchial stump has been reinforced with a thymic fat pad. The pericardial patch is fenestrated to prevent tamponade.

Step Four: Reconstruction

The bronchial stump is reinforced with a tissue flap, usually from either pericardial fat or a thymic fat pad. The hemithorax is then irrigated with warm saline and water to remove residual microscopic tumor. The pericardium and diaphragm are then reconstructed using Gore-Tex patches (Gore-Tex, Inc., Flagstaff, AZ) to prevent any subsequent herniation of the heart or abdominal contents into the empty hemithorax. The pericardial patch must be fenestrated to prevent any constrictive physiology occurring postoperatively. The chest is then closed in the usual fashion once hemostasis has been achieved.

PATIENT SELECTION

Estimates have suggested that only 1% to 5% of all patients with mesothelioma might be suitable for surgery.²⁰ Selection of appropriate patients for EPP is crucial, and varies between different centers although the principles remain the same. Table 14–2 lists commonly used patient selection criteria.

Table 14-2. Suggested Selection Criteria for Extrapleural Pneumonectomy

Importantly for a patient to be considered for an EPP, they should have a good performance status. This is defined as Eastern Cooperative Oncology Group (ECOG) Performance Status 0-1 (Table 14–3).²¹ Patients should have adequate pulmonary function to tolerate a pneumonectomy, with predictive forced expiratory volume in 1 second (FEV₁) greater than 1 liter. All patients with predictive FEV₁ less than 2 liters are recommended to undergo radionucleotide ventilation-perfusion scanning to assess the contribution of the diseased lung, and improve the accuracy of the predicted postoperative value. Arterial blood gases are obtained to rule out baseline hypoxia and/or hypercapnia.

Table 14-3. Eastern Cooperative Oncology Group (ECOG) Performance Status

Two-dimensional dobutamine echocardiography is necessary to rule out ventricular dysfunction (EF <45%), significant coronary artery disease, and pulmonary hypertension (mean pulmonaryartery pressure >30 mm Hg) that may increase perioperative risks.

Patients potentially suitable for radical surgery have epithelioid tumors of low volume. Studies have consistently demonstrated the significance of epithelial histology in the outcomes of mesothelioma patients.²² The International Mesothelioma Interest Group (IMIG) developed a new staging system in 1994 based on the TNM system of lung cancer.²³ Stages I and II disease are both N0M0, meaning there is no evidence of regional lymph node or distant metastases respectively. Accurate preoperative staging requires CT, MRI, PET, and often thoracoscopy and mediastinoscopy. Final staging is only possible at surgery.

ANESTHETIC MANAGEMENT

Anesthesia for EPP is challenging with a high rate of perioperative morbidity. There are a number of potential management problems in addition to the standard anesthetic issues for a pneumonectomy. The major additional anesthetic issues are listed in Table 14–4.

Table 14–4. Major Anesthetic Issues for Extrapleural Pneumonectomy

Most importantly EPP is associated with significant extra blood loss as small blood vessels are disrupted during the blunt dissection of the pleura. There is also the potential for acute blood loss if major blood vessels are disrupted. This can be accompanied by alterations in preload and cardiac output caused by surgical pressure on the pericardium and great vessels. Therefore, the anesthetic plan needs to be tailored to expect hemodynamic instability and major fluid shifts.

Planning—Lines, Monitors, and Equipment

Adequate venous access is essential in these patients. If large-bore peripheral intravenous access cannot be obtained, it is prudent to insert a wide-bore central line for rapid infusion of blood products. Invasive arterial and central venous monitoring are routine. A method of delivering blood products rapidly should be available, and blood should be in the operating room. Pulmonary artery catheters are rarely used, and the data have been shown to be difficult to interpret during pneumonectomy.²⁴ Transesophageal echocardiography (TEE) should be available to assess right and left ventricular filling and function if needed. Vasoconstricting agents should be available, especially for large tumors and if epidural anesthesia is to be used intraoperatively. It is essential that patients are adequately warmed, so appropriate use of warming devices and fluid warmers is recommended.

Thoracic Epidural Anesthesia

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