Mediastinal Mass and Superior Vena Cava Syndrome




Mediastinal Mass and Superior Vena Cava Syndrome



Daniel Kalowitz, Menachem M. Weiner



Abstract


An anterior mediastinal mass is one of the most challenging pathologies an anesthesiologist may face during his or her career. To safely care for these patients, it is imperative to know the relevant anatomy of the mediastinum, understand how mediastinal pathology can compromise a patient’s respiratory and cardiovascular systems, and recognize how to prepare for and quickly treat these potentially life-threatening complications. In this chapter, we will present a case of an anterior mediastinal mass with superior vena cava syndrome. We will discuss the important preoperative testing, preanesthetic considerations, risk stratification, and intraoperative anesthetic management. We will also present a flowchart with potential management strategies to assist in safely caring for the majority of these patients.


Keywords


mediastinal mass; SVC syndrome; airway collapse; anesthetic preparation; mediastinal anatomy



Introduction


An anterior mediastinal mass is one of the most challenging pathologies an anesthesiologist may face during his or her career. To safely care for these patients, it is imperative to know the relevant anatomy of the mediastinum, understand how mediastinal pathology can compromise a patient’s respiratory and cardiovascular systems, and recognize how to prepare for and quickly intervene to treat these potentially life-threatening complications. In this chapter, we will present a case of an anterior mediastinal mass with superior vena cava syndrome (SVCS). We will discuss the important preoperative testing, preanesthetic considerations, risk stratification, and intraoperative anesthetic management. We will also present a flowchart with potential management strategies to assist in safely caring for the majority of these patients.



Case Presentation


A 30-year-old female with no significant past medical history presents to the emergency department with dyspnea, inability to lie flat, cough, and chest discomfort that has progressively worsened over the past few weeks. Clinical examination findings are notable for engorged neck veins with head and upper extremity swelling. Following admission to the hospital, a subsequent workup reveals a very large anterior mediastinal mass associated with both tracheal and great vessel compression. A malignancy is suspected, and the plan is to obtain a tissue sample for histologic diagnosis followed by surgical resection by a multidisciplinary team.



Review of the Literature



Anatomy and Pathophysiology


The mediastinum is the area within the chest bounded anteriorly by the sternum, posteriorly by the vertebral column, laterally by the two parietal pleura, inferiorly by the diaphragm, and superiorly by the thoracic inlet.1 Some authors divide it into four compartments: the superior, anterior, middle, and posterior compartments. The superior compartment is bound superiorly by the thoracic inlet and inferiorly by the plane extending from the sternal angle anteriorly to the lower border of the fourth thoracic vertebrae posteriorly.2 The anterior, middle, and posterior compartments are bound superiorly by this plane, inferiorly by the diaphragm, and are divided in the anterior to posterior direction based on the pericardium2,3 (Fig. 34.1). Others argue that because there is no true anatomic boundary separating the superior and anterior compartments, it is considered one compartment, the anterosuperior compartment, and that the mediastinum is made up of three distinct compartments: the anterosuperior, middle, and posterior compartments1,3 (Fig. 34.2).


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• Fig. 34.1 Four-compartment model of the mediastinum. (From Liu W, Deslauriers J. Mediastinal divisions and compartments. Thorac Surg Clin. 2011;21(2):183–190.)

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• Fig. 34.2 Three-compartment model of the mediastinum. (From Liu W, Deslauriers J. Mediastinal divisions and compartments. Thorac Surg Clin. 2011;21(2):183–190.)

Regardless of whether there are three or four mediastinal compartments, it is important to realize that these compartments cannot be treated as separate entities. Masses in one compartment often extend and affect structures in other compartments. Anterior masses often invade the middle compartment, and masses in the anterior and middle compartments may have similar effects.4 Furthermore, many of the lesions in the superior compartment originate from or extend into the anterior compartment.1 In addition, although the majority of complications are described for anterior mediastinal masses, masses in the middle and posterior mediastinum have also been associated with hemodynamic and respiratory collapse with induction of general anesthesia.


There are many vital structures within the mediastinum that can be affected by the presence of masses3 (Fig. 34.3). The anterosuperior compartment contains the lower trachea, the aortic arch and its branches, the super vena cava, and the azygous vein. The middle compartment contains the heart, the carina and mainstem bronchi, the pulmonary hila, and the terminal portion of the superior vena cava. The posterior compartment contains various nerves and nerve roots, the sympathetic chain, the descending aorta, the esophagus, and the azygous vein.1


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• Fig. 34.3 Structures in the mediastinum. (From Liu W, Deslauriers J. Mediastinal divisions and compartments. Thorac Surg Clin. 2011;21(2):183–190.)

Mediastinal masses can be primary or metastatic tumors5,6 (Fig. 34.4; Table 34.1). Metastatic tumors are relatively common, whereas primary tumors are quite rare and are often benign.5 The most common anatomic location and histologic type of mediastinal tumor differs by age.4 In children, there is an increased incidence of neurogenic tumors, particularly neuroblastomas, and masses are predominantly found in the posterior mediastinum.1,4 In adolescents, lymphomas in the anterior mediastinum are the most common.1 In adults, masses are seen most frequently in the anterosuperior compartment,1 and are most often thymomas and lymphomas.7


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• Fig. 34.4 Types and locations of mediastinal tumors. (From Salgia R, Blanco R, Skarin AT. Lung cancer and tumors of the heart and mediastinum. In: Skarin AT, ed. Atlas of Diagnostic Oncology. 4th ed. Philadelphia: Elsevier; 2010:98–159.)


Table 34.1





















Malignant and Benign Mediastinal Tumors by Location
Compartment Malignant Tumors Benign Tumors
Anterior Lymphoma

Mixed germ cell


Seminoma


Thymic carcinoma


Thymic carcinoid


Thyroid carcinoma

Cystic hygroma

Foramen of Morgagni hernia


Parathyroid adenoma


Thymic cyst


Thymic hyperplasia


Thymolipoma


Thymoma


Thyroid

Middle Esophageal cancer

Lymphoma


Metastases


Thyroid carcinoma

Benign adenopathy

Cardiac and vascular structures


Cardiophrenic fat pad


Cysts


Ectopic thyroid


Esophageal mass


Foramen of Morgagni hernia


Hiatal hernia


Lipomatosis

Posterior Neuroblastoma Neurofibroma

Schwannoma


Chemodectoma


Foramen of Bochdalek hernia Meningocele


Modified from Yoneda KY, Louie S, Shelton DK. Mediastinal tumors. Curr Opin Pulm Med. 2001;7(4):226–233.


A growing mass in the mediastinum has the potential to interfere with many of the important structures contained within it and cause a variety of symptoms. When adding the physiologic changes seen under general anesthesia, even an asymptomatic patient can develop severe, and potentially fatal, complications.



Preanesthetic Assessment



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



Table 34.2











Symptoms and Clinical Findings in Patients With Mediastinal Masses and Superior Vena Cava Syndrome
Symptoms Clinical Findings
Cough

Dyspnea


Orthopnea


Hoarseness


Nasal stuffiness


Fatigue


Chest pain


Faintness


Headache


Altered mentation


Distorted vision


Dysphagia

Cyanosis

Wheezing


Decreased breath sounds


Pleural effusions


Stridor


Vocal cord paralysis


Syncope


Pulsus paradoxus


Altered mentation


Horner syndrome


Upper extremity swelling


Head and neck vein dilation


Papilledema


Modified from Narang S, Harte BH, Body SC. Anesthesia for patients with a mediastinal mass. Anesthesiol Clin North Am. 2001;19(3):559–579; and Pullerits J, Holzman R. Anaesthesia for patients with mediastinal masses. Can J Anaesth. 1989;36(6):681–688.


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.


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• Fig. 34.5 Bronchoscopic image showing external tracheal compression.

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 surroundings9,19 (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 branches1,4,20 (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.


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• Fig. 34.6 Posterior-anterior (A) and lateral (B) chest x-rays in a patient with an anterior mediastinal mass and superior vena cava syndrome. (From Broder J. Diagnostic Imaging for the Emergency Physician. Philadelphia: Elsevier; 2011.)

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• Fig. 34.7 Contrast enhanced computed tomography chest (A, axial) (B, coronal) showing a mediastinal mass with narrowing of the right pulmonary artery (arrow). (From Hayes SA, Plodkowski AJ, Ginsberg MS. Imaging of thoracic cavity tumors. Surg Oncol Clin N Am. 2014;23(4):709–733.)

image
• Fig. 34.8 Magnetic resonance imaging of the chest in a patient with a mediastinal mass. (From Carrier G, Fréchette E, Ugalde P, Deslauriers J. Correlative anatomy for the sternum and ribs, costovertebral angle, chest wall muscles and intercostal spaces, thoracic outlet. Thorac Surg Clin. 2007;17(4):521–528.)

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.


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• Fig. 34.9 Midesophageal transesophageal echocardiography imaging (A, Midesophageal ascending aorta short axis view) (B, Midesophageal ascending aorta long-axis view) showing a mediastinal mass posterior to the ascending aorta. (From Brooker RF, Zvara DA, Roitstein A. Mediastinal mass diagnosed with intraoperative transesophageal echocardiography. J Cardiothorac Vasc Anesth. 2007;21(2):257–258.)

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 distorted25,26 (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.


image
• Fig. 34.10 Pulmonary function tests seen in patients with an intrathoracic mass. RV, Right ventricular; TLC, Total lung capacity. (From: Gerlac RM, Klafta JM. Mediastinal masses, complications in anesthesia. In: Fleisher LA, Rosenbaum SH (eds). 3rd ed. Philadelphia: Elsevier; 2018:262–265.)

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.



Risk Stratification


The increased anesthetic risk in patients with mediastinal masses is caused by the possibility of worsening compression of the pulmonary tree and/or cardiovascular structures and the subsequent effect on those systems. Compression of any part of the pulmonary tree can lead to a loss of the airway and difficulty with oxygenation and ventilation. It can lead to hypoxia, hypercarbia, ventilation-perfusion mismatch, and potential respiratory collapse. Compression of the heart or of any major vessels can lead to hypotension, decreased cardiac preload, increased afterload, and the potential for cardiovascular collapse. It is important to recognize that any or all of these complications can occur abruptly during any point during the perioperative period, although they appear to be most commonly seen on induction of anesthesia. Being able to recognize the symptoms and clinical findings that indicate a higher likelihood of perioperative complications is a tool every anesthesiologist must have in their armamentarium.


Some practitioners believe that in the absence of preoperative airway obstruction and severe clinical symptoms, general anesthesia may be safely induced in patients with anterior mediastinal masses. Ferrari et al.33 conducted a chart review of 44 pediatric patients admitted to Memorial Sloan-Kettering Cancer Center with a diagnosis of anterior mediastinal mass that required surgery. No patient died or sustained permanent injury as a result of their anesthetic or operative experience. Of the nine patients with preoperative respiratory symptoms, two patients experienced difficulty on induction of anesthesia and required tracheal intubation with a rigid bronchoscope. Two others developed airway obstruction during anesthetic maintenance that was corrected with changes in patient position. The authors concluded that in the absence of life-threatening preoperative airway obstruction and severe clinical symptoms, general anesthesia may be safely induced before radiation therapy. Despite the authors conclusion, in that study, 4 out of 44 patients required unconventional measures to maintain oxygenation during induction of anesthesia, using a rigid bronchoscopy or turning the patient in the lateral position to alleviate the tracheal compression. It is up to the anesthesiologist to consider the pros and cons of induction versus awake fiberoptic intubation.


However, perioperative complications can be seen in patients without preoperative symptoms or clinical findings,34–36 and certain symptoms and clinical findings have been found to be associated with increased anesthetic risk (Box 34.1). One additional symptom to take seriously is syncope during a forced Valsalva maneuver, such as during a bowel movement, as this maneuver can further diminish venous return, and this may suggest significant cardiac or pulmonary artery compression.2


Oct 6, 2021 | Posted by in ANESTHESIA | Comments Off on Mediastinal Mass and Superior Vena Cava Syndrome
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