Presenting Symptoms and Clinical Findings

Perioperative complications are associated with cardiorespiratory signs and symptoms at initial presentation.⁸ An anesthesiologist caring for these patients must be able to identify the variety of clinical signs and symptoms of a mediastinal mass (Table 34.2).^1,2 The patient can also present with no symptoms at all. In children with mediastinal tumors, the incidence of symptoms at presentation is about 70%.⁹ Their relatively soft airways make them more susceptible to compression by a mass, and there might be a history of cough, dyspnea, and frequent respiratory infections.¹⁰ Roughly 40% of all tumors involving the mediastinum are asymptomatic at presentation. Consequently, these masses regularly grow to such a size that determination of the site of origin is challenging. Regardless of the definitive diagnosis, the exact size, or location, all large mediastinal and intrathoracic masses may cause mechanical compression of vital mediastinal structures, purely because of the sheer weight and volume of the tumor. Acute or chronic respiratory insufficiency may occur with compression of the airways. Hemodynamic decompensation can be caused by compression of the heart or major vessels in the mediastinum. As mentioned before, these effects can be greatly aggravated by induction of anesthesia or positional changes during surgery and can lead to life-threatening situations.⁹ Those patients who are symptomatic often have vague and nonspecific complaints that can often be referred to the respiratory and/or cardiovascular systems.² The most common complaints in adults are cough, chest pain, dyspnea, and dysphagia.^1,10

SVCS is a group of symptoms caused by an obstruction of the SVC. It is seen in 28% of patients with a mediastinal mass.⁷ Historically, 40% of the cases with SVCS were caused by obstruction, resulting from syphilitic aneurysms and tuberculosis mediastinitis.¹¹ Presently, SVCS is almost always secondary to an obstruction caused by a mediastinal tumor.¹¹ It is more frequently seen in patients with diffuse histiocytic lymphoma, in those with lesions on the right side of the body, and those with an obstruction below the azygous vein drainage into the SVC.¹² The most common symptom for SVCS is dyspnea, with facial and periorbital edema being an early sign of this disease process.² Other signs and symptoms of SVCS depend on the speed at which the obstruction progresses and can include upper extremity swelling, plethora, head and neck vein dilation, headaches, mental status changes, and visual disturbances.

Diagnostic Testing

Early reports in the 1970s and 1980s found increased risks of respiratory complications in patients with mediastinal tumors undergoing general anesthesia.^13,14 Since then, many additional reports have been published that highlight the increased risk of cardiovascular complications as well.^15,16 Whereas many of these reports have occurred in children with mediastinal masses undergoing anesthesia, adults with mediastinal tumors are at the same risk. The correlation of perioperative complications to mediastinal mass size and location, as well as cardiorespiratory signs and symptoms at presentation, highlight the critical importance of a thorough preanesthetic clinical workup.^8,17

Diagnostic imaging is the mainstay of the preoperative evaluation of these patients. With the exception of a true surgical emergency, all patients with suspected or known mediastinal masses should have a radiologic evaluation of the mass. Because mediastinal masses may grow quickly within 2 to 3 weeks, it is important to perform these imaging tests as close to the proposed anesthetic as possible.^1,2 The decision to use magnetic resonance (MR), computed tomography (CT), x-ray, and/or angiography depends on the location and type of lesion. CT and MR imaging are especially useful for the preanesthesia evaluation, as they are performed in the supine position and may detect positional compression of the airway, heart, or great vessels by the mass that may be further accentuated under anesthesia.¹ If the compression of the trachea at any point is greater than 50% of the tracheal diameter (Fig. 34.5), it should immediately raise a red flag that will require meticulous preparation before induction of anesthesia.

Chest x-ray is often the first imaging modality to be performed and can provide valuable information. Because of the two-dimensional nature of the image, it is important to obtain both anterior-posterior and lateral images (Fig. 34.6).¹⁸ CT is perhaps the most commonly used imaging modality, and it has been accepted that all patients with a mediastinal mass should have CT imaging.¹ CT has superior spatial resolution⁹ and can determine the morphology of the tumor, its exact anatomic location, and define its relation to the surrounding mediastinal structures.⁴ Intravenous contrast may be used with CT imaging to delineate the vascularity of the tumor and its surroundings^9,19 (Fig. 34.7). MR imaging is superior in identifying vascular compression and tissue invasion,¹ and distinguishing soft tissues from vascular structures.⁹ In 25% of patients, MR may show more extensive disease than CT. It is the imaging modality recommended for neurogenic lesions, vascular abnormalities, and those disease processes involving the aortic arch and branches^1,4,20 (Fig. 34.8). Other uncommon modalities that may be seen are scintigraphy and positron emission tomography (PET), which is not used for primary imaging but can be used to follow up germ-cell tumors after initial treatment. Kitami et al.²¹ performed a retrospective analysis of 109 patients to evaluate the usefulness of PET/CT findings in the classification and management of anterior mediastinal tumors. They found that the sensitivity, specificity, and accuracy of ¹⁸F-fluorodeoxyglucose (FDG) in the detection of low-grade thymomas and thymomas with a maximum diameter of 50 mm or less and a standardized uptake value maximum of 3.4 or less (>2 is suggestive of malignancy SUV’s=Standardized Uptake Values) were 85%, 48%, and 60%, respectively. The authors concluded that FDG-PET/CT is an objective and useful modality in the differential diagnosis and management of anterior mediastinal tumors.

Regardless of the imaging technique used, the anesthesiologist must personally review the images. A radiologist’s report may not provide enough detail regarding the level of airway obstruction, tumor position, and cardiac compression that is crucial for the anesthesiologist for the safe care of these patients.¹

Preoperative echocardiography is another diagnostic test that may be recommended for some patients. Echocardiography to assess a patient’s cardiac structure and function can provide valuable information for the risk stratification of these patients.⁹ Transthoracic echocardiography may be performed in both the supine and lateral positions to help detect positional changes on compression of the heart and the great vessels. Transesophageal echocardiography (TEE) has been shown to help detect the invasion of cardiac cavities and the vena cava. It can provide valuable information to help determine whether cardiac surgery standby is required.²² Anderson et al.²³ reported a case of a patient with a posterior mediastinal mass requiring urgent cardiopulmonary bypass which was delineated by the perioperative TEE. Brooker et al.²⁴ reported a case where, after a pericardial window and chest tube placement for a pericardial effusion, TEE newly identified a mediastinal mass that encased the ascending aorta and pulmonary artery that was previously missed on preoperative chest x-ray and surface echocardiography (Fig. 34.9).²⁴ In addition, TEE can be a useful tool for improved staging of thymoma patients before surgery, which is the treatment of choice whenever a complete resection may be accomplished. After surgery, all thymomas, except completely encapsulated stage I tumors, should be treated with postoperative adjuvant radiation.

The usefulness of preoperative pulmonary function tests (PFTs) appears to be the most controversial aspect of the preoperative assessment. Patients with mediastinal masses have flow volume loops that correlate with a fixed lesion because of a reduction in peak inspiratory and expiratory flows, which is usually the first value to be distorted^25,26 (Fig. 34.10). In 1984, Neuman et al.²⁷ stated that every patient should obtain upright and supine flow volume loops, as it is the most sensitive noninvasive way to diagnose airway obstruction. However, more recent opinions appear to disagree with this. Many have found that although PFTs can confirm the presence of obstructive or restrictive defects, they do not correlate with perioperative outcomes or anatomic abnormalities, and provide no additional useful information compared with chest imaging,^1,4,28–31 A study by Hnatiuk et al.³² looked at 37 patients with anterior mediastinal masses at the Walter Reed Army Medical Center over a 6-year period. Spirometry in the upright and supine positions was suggestive of possible upper airway obstruction in four patients. However, general anesthesia was used in all four patients without complications. The authors concluded that the recommendation to perform PFTs was anecdotal and PFTs were not better than imaging and symptoms at predicting perioperative complications.

It is important to note that if thymus or thyroid pathology is suspected, an anesthesiologist must recognize the endocrinologic risks associated with these abnormally functioning glands. The possibility of thyroid storm, myxedema coma, and myasthenia gravis, among other disease processes, must be considered. The management of these disorders, however, is beyond the scope of this chapter.