Chapter 12 Thoracic Surgery

In this chapter the care of patients undergoing noncardiac thoracic surgery is discussed. The emphasis is on postoperative care, but preoperative evaluation and intraoperative management are also reviewed. Thoracic surgery patients, particularly those undergoing pulmonary resection or lung volume reduction surgery (LVRS), are commonly elderly, current or former heavy smokers, and highly likely to have other smoking-related diseases. Careful preoperative selection and optimization are essential for good postoperative outcomes.

This chapter is divided into two sections: (1) pulmonary resection; (2) other thoracic surgery. Pulmonary resection is essentially a discussion of the diagnosis, selection, treatment, and postoperative care of patients undergoing surgery for lung cancer. Other topics covered include LVRS, mediastinal tumors, and esophageal resection. Thoracic trauma, massive hemoptysis, and empyema are covered in Chapters 25, 26, and 35.

PULMONARY RESECTION

Major pulmonary resection is sometimes undertaken for infective lung disease but the great majority of patients who undergo pulmonary resection do so for lung cancer.

Surgery for Lung Cancer

Classification

Syndrome (hormone secretion)	Clinical Manifestation	Cancer
Hypercalcemia (parathyroid)	Hypercalcemia, polyuria, hypovolemia, confusion	NSCLC
SIADH (ADH)	Hypernatremia	SCLC/NSCLC
Cushing syndrome (ACTH, CRH)	Hypertension, fluid retention, weakness, hypokalemia, hyperglycemia	SCLC/Carcinoid
Acromegaly (GH, GHRH)	Bony overgrowth	SCLC/Carcinoid
Gynecomastia (HCG)	Breast enlargement	SCLC/NSCLC
Myositis/myopathy	Proximal weakness, myalgia	SCLC/NSCLC
Myasethenic syndrome	Weakness, fatigability	SCLC
Brain/spinal cord/peripheral neuropathy	Multiple	SCLC

ACTH, adrenocorticotropic hormone; ADH, antidiuretic hormone; CRH, corticotropin releasing hormone; GH, growth hormone; GHRH, growth hormone releasing hormone; HCG, human chorionic gonadotropin; NSCLC, non-small cell lung cancer; SCLC, small cell cancer; SIADH, syndrome of inappropriate antidiuretic hormone secretion.

Occasionally, lung cancer is asymptomatic and is an incidental finding on a routine chest radiograph. The presence of a large noncalcified mass (<3 cm in diameter) with spiculated margins is highly suggestive of malignancy. The chest radiograph may show consolidation distal to the mass, mediastinal lymphadenopathy, or pleural effusion. Recently, there has been interest in screening high-risk, asymptomatic patients by means of computed tomography (CT) scanning.¹

Surgical Suitability for Resection

Lung cancer is staged according to the TNM (tumor, node, metastases) classification (Tables 12-2 and 12-3). All patients being considered for surgery should have a CT scan of the chest, liver, and adrenal glands. Percutaneous needle biopsy may be considered for peripheral lesions but is not mandatory. Patients with mediastinal lymph nodes greater than 1 cm diameter on CT scan should undergo a staging biopsy or mediastinoscopy prior to lung resection. The presence of a malignant effusion is a contraindication to surgery, but an effusion due to consolidation distal to an obstructing lesion is not; if there is doubt, a pleural aspirate should be obtained.

Table 12-2 TMN Classification of Lung Cancer

Primary Tumor (T)
T_x	Primary tumor cannot be assessed or proven
T₀	No evidence of primary tumor
T_is	Carcinoma in situ
T₁	Tumor <3 cm in greatest dimension, surrounded by lung or visceral pleura, without evidence of invasion more proximal than lobar bronchus
T₂	Tumor with any of the following features: >3 cm in greatest dimension involves main bronchus >2 cm distal to the carina invades the visceral pleura associated with atelectasis or obstructive pneumonitis that extends to the hilar region but does not involve the entire lung
T₃	Tumor of any size that directly invades the following: chest wall, diaphragm, mediastinal pleura, parietal pericardium; or tumor in the main bronchus <2 cm distal to the carina but without carinal involvement; or associated atelectasis or obstructive pneumonitis of the whole lung
T₄	Tumor of any size that involves any of the following: mediastinum, heart, great vessels, trachea, esophagus, vertebral body, carina; or tumor with a malignant pleural or pericardial effusion or with satellite tumor nodule within the ipsilateral primary tumor lobe of the lung
Regional Lymph Nodes (N)
N_x	Regional nodes cannot be assessed
N₀	No regional lymph node metastases
N₁	Metastases to ipsilateral peribronchial and/or ipsilateral hilar lymph nodes and intrapulmonary nodes involved by direct extension of primary tumor
N₂	Metastases to ipsilateral mediastinal and/or subcarinal nodes
N₃	Metastases to contralateral mediastinal, contralateral hilar, ipsilateral, or contralateral scalene or supraclavicular lymph nodes
Distant Metastases (M)
M_x	Presence of distant metastases cannot be assessed
M₀	No distant metastases
M₁	Distant metastases present (includes those in a different lobe of the same lung)

British Thoracic Society, Society of Cardiothoracic Surgeons of Great Britain and Ireland Working Party: BTS guidelines: guidelines on the selection of patients with lung cancer for surgery. Thorax 56:89-108, 2001.

Table 12-3 Stage Grouping TNM Subsets for Lung Cancer

Patients who have non-small cell cancer in stage I or II are considered operable: stage I disease has a high chance of cure with surgery alone; stage II disease has a moderate chance of cure with surgery alone. Patients with stage IIIA have a low chance of cure with surgery alone but may be considered for operation in conjunction with chemotherapy. Stage IIIB with known N2 involvement and stage 4 tumors are generally considered inoperable. Adjuvant chemotherapy in all but stage IA leads to improved survival rates, but benefits resulting from postoperative radiotherapy following complete primary tumor resection have not been proven.

Fitness for Pulmonary Resection

Curative lung resection involves the removal of a considerable amount of tissue, which results in permanent loss of pulmonary function. Quantitative assessment of pulmonary function is therefore important for stratifying a patient’s surgical risk. However, given that the outcome of nonsurgical treatment of lung cancer is very poor, it may still be appropriate to proceed with pulmonary resection in a patient deemed to be at high risk based on the results of lung function tests.²^–⁵

Routine Assessment

Many patients undergoing pulmonary resection are elderly. Advanced age (<80 years) does not itself preclude pulmonary resection. However, pneumonectomy is associated with an increased risk for mortality in elderly patients, and age should be a factor in deciding suitability for surgery in this patient group.² The patient’s general clinical state should be evaluated, including changes in exercise capacity or the occurrence of weight loss or anemia. Preoperative weight loss of more than 10%, a body mass index less than 18.5, and a low serum albumin are markers of advanced disease and indicate increased perioperative risk.

All patients should undergo simple spirometry and oximetry measurements prior to pulmonary resection. Some centers also measure the pulmonary diffusing capacity of carbon monoxide (DL_CO) in all patients. A forced expiratory volume in the first second (FEV₁) that is greater than 1.5 l is considered adequate for lobectomy; an FEV₁ greater than 2 l is considered adequate for pneumonectomy. Values less than those are indications for further pulmonary testing. A resting arterial carbon dioxide tension greater than 6 kPa (45 mmHg) also indicates increased perioperative risk.

Pulmonary Assessment of High-Risk Patients

Patients who are not clearly suitable for pulmonary resection on the basis of simple spirometry should undergo further testing for pulmonary function.

Predicted Postoperative FEV₁.

The predicted postoperative FEV₁ (ppoFEV₁) is calculated from the preoperative FEV₁ (preopFEV₁) and the proportion of functional lung that is to be removed (Fig. 12-1). The most accurate way to measure the functional contribution of the lung tissue to be resected is by means of split perfusion scanning using technetium (Tc⁹⁹) macroaggregates or quantitative CT scanning.⁶ A simple alternative is to estimate the proportion on the basis of the number of anatomic pulmonary segments that are to be removed (Fig. 12-2). To allow safe resection, the predicted postoperative FEV₁ should be greater than 40% of normal.

Figure 12.1 Algorithm for selection of patients for pulmonary resection. DL_CO, diffusion capacity of the lungs for carbon monoxide (transfer factor); FEV₁, forced expiratory volume in 1 second; ppo, predicted postoperative; S_ao₂, arterial oxygen saturation: one shuttle is equal to 10 meters; VO_{2 max}, oxygen consumption during maximal exercise.

(From British Thoracic Society, Society of Cardiothoracic Surgeons of Great Britain and Ireland Working Party: BTS guidelines: guidelines on the selection of patients with lung cancer for surgery. Thorax 56;89-108, 2001.)

Figure 12.2 Bronchopulmonary segments. There are 20 anatomic bronchopulmonary segments, 10 in each lung. Two segments in the left lower lobe are small and are functionally equivalent to one segment. Thus, there are 19 functional segments: 10 in the right lung and 9 in the left lung. LLL, left lower lobe; LUL, left upper lobe; RLL, right lower lobe; RML, right middle lobe; RUL, right upper lobe.

Diffusing Capacity.

The DL_CO provides a measure of the severity of parenchymal lung disease—although the measurement probably reflects ventilation-perfusion inequalities rather than impaired function of the alveolar capillary membrane. Reduced DL_CO is strongly associated with adverse postoperative outcome. Historically, patients undergoing pulmonary resection with a preoperative DL_CO of less than 60% of the predicted value experienced a mortality rate of 25% and a pulmonary morbidity rate of 45%.⁷ More recent data suggest that if the preoperative DL_CO is greater than 45% of the predicted value, acceptable surgical results may be obtained.⁸

Exercise Testing.

Exercise tests are a measure of functional cardiorespiratory reserve. They include the shuttle walk, the 6-minute walk, exercise oximetry, and oxygen consumption during maximal exercise (Vo_{2 max}). Of these tests, Vo_{2 max} is the most widely used.

A Vo_{2 max} of less than 15 ml/kg/min indicates a high risk for developing a postoperative cardiorespiratory complication following lung resection.³ A Vo_{2 max} less than 10 ml/kg/min (<40% predicted) indicates that the patient is unsuitable for any form of pulmonary resection, whereas a value greater than 20 ml/kg/min (<75% of predicted) indicates resection up to pneumonectomy is reasonable.³ As with FEV₁ and DL_CO, a predicted postoperative Vo_{2 max} can also be calculated; a value less than 10 ml/kg/min (<40% predicted) indicates unsuitability for pulmonary resection.⁹

Patients who cannot complete 25 shuttles (250 m) on a shuttle walk or who desaturate more than 4% during a 6-minute walk are also at increased risk for postoperative pulmonary complications. In the absence of sophisticated exercise tests, cardiorespiratory reserve can be estimated by stair climbing. The ability to walk three or more flights of stairs (12 steps per flight) is associated with acceptable risk for lobectomy, and completion of five or more flights indicates suitability for pneumonectomy.

Integrated Approach to Pulmonary Testing

A number of algorithms have been proposed for pulmonary testing to identify high-risk patients and assess their suitability for surgery. One algorithm, proposed by the British Thoracic Society, is shown in Figure 12-1.²

Preoperative Cardiovascular Evaluation

Patients undergoing pulmonary resection are at increased risk for coronary artery disease. All patients should have a preoperative electrocardiogram and, if a murmur is present, an echocardiogram. Surgery should be delayed for at least 6 weeks following a myocardial infarction.

Clinical predictors of increased perioperative cardiac risk are summarized in Table 12-4. Patients at major risk should have a formal cardiologic assessment, and those with severe coronary artery or valvular lesions should be considered for a revascularization procedure or valve surgery prior to pulmonary resection. Patients at intermediate risk who have good functional capacity do not require further cardiac investigation but, in the presence of poor functional capacity, referral to a cardiologist and cardiac stress testing are warranted. Patients at increased risk for cerebrovascular disease (e.g., a carotid bruit or a history of stroke or transient ischemic attack) should undergo a preoperative carotid Doppler ultrasound study.

Table 12-4 Predictors of Increased Cardiovascular Risk Following Major Noncardiac Surgery

Major Predictors

Unstable coronary syndromes: recent myocardial infarction with evidence of important ischemic risk based on symptoms or noninvasive study; unstable or severe angina

Decompensated congestive cardiac failure

Significant cardiac arrhythmias: high-grade atrioventricular block; symptomatic ventricular arrhythmias in the presence of underlying heart disease; supraventricular arrhythmias with uncontrolled ventricular rate

Severe valvular heart disease

Intermediate Predictors

Mild angina

Previous myocardial infarction based on history of pathologic Q waves

Compensated or prior congestive cardiac failure

Diabetes

Minor Predictors

Advanced age

Abnormal ECG findings (e.g., left ventricular hypertrophy, left bundle branch block, ST or T wave abnormalities)

Rhythm other than sinus rhythm (e.g., atrial fibrillation)

History of stroke

Poorly controlled hypertension

Adapted from Eagle KA, Berger PB, Calkins H, et al: ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery—executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). J Am Coll Cardiol 39:542-553, 2002; and from British Thoracic Society, Society of Cardiothoracic Surgeons of Great Britain and Ireland Working Party: BTS guidelines: guidelines on the selection of patients with lung cancer for surgery. Thorax 56:89-108, 2001.