• Anterior mediastinal masses include teratomas, thyroid tumors, lymphomas, and thymomas. They can result in dangerous and fatal cardiovascular or pulmonary structure compression at the time of anesthesia induction, muscle relaxation, and positive pressure ventilation.
• Patients present to the operating room for biopsy or excision of the mass via a sternotomy, thoracotomy, cervical mediastinoscopy, anterior parasternal mediastinoscopy, video-assisted thoracoscopic biopsy, or awake CT-guided percutaneous biopsy.
• There are also case reports of patients with undiagnosed anterior mediastinal masses (AMM) presenting emergently to the operating room for ascending aortic aneurysm and Cesarean sections (1).

• Depends on tissue diagnosis of mass, usually secondary to a mutation
• Often an incidental finding

• During spontaneous ventilation (SV), airways are held open by baseline negative intrathoracic pressures and adherence of the pleura to the chest wall.
• Intrathoracic versus extrathoracic masses:
  • Intrathoracic masses are found within the chest cavity. During SV, inspiration expands the rib cage upward and outward and "lifts" the mass off vascular and respiratory structures. In the standing position, exhalation does not typically result in symptoms. However, in the recumbent and supine positions, exhalation can result in compression of structures.
  • Extrathoracic masses are located outside the chest cavity and are further divided into variable and fixed lesions.
    • Variable lesions: Redundant airway tissue (snoring), tracheomalacia, etc. During SV, obstruction occurs during inspiration. The negative pressure that is generated in the chest, distal to the mass, results in collapse of the airway. During exhalation, the position pressure that is generated by the abdominal muscles, distal to the mass, stent the airway open.
    • Fixed lesions: Goiter. Obstruction to airflow occurs during inspiration and exhalation.
• AMMs (intrathoracic masses) can result in extrinsic compression of structures:
  • Respiratory: Trachea, major bronchus. The mass may prevent adequate ventilation by compressing the trachea/bronchus while perfusion remains unchanged. This can result in a V/Q mismatch called a pulmonary shunt.
  • Cardiovascular: Great vessels, right ventricular outflow tract (posterior mediastinal masses are more likely to affect the left atrium or ventricle). Encroachment does not produce hemodynamic effects, whereas compression results in clinical manifestations similar to pericardial tamponade. Right ventricular failure may be responsible for hypotension with resultant dead space lung physiology (blood flow to the alveoli is decreased; hypoxemia can result even in the absence of tracheal obstruction).
• Infants and children have more compressible airways and may be more susceptible than adults to extrinsic airway obstruction (1).
• Superior vena cava (SVC) syndrome: The thin-walled venous system is easily compressible by a large mediastinal mass. Thus, if there is obstruction to venous drainage from the upper body, this can cause interstitial edema. Therefore, collateral veins with low resistance become dilated.

• Management depends on the anatomy and pathology of the mass, as well as the surgical procedure.
• Look for compression of the heart, great vessels, and airway structures during induction and throughout the surgical procedure.

• Respiratory symptoms: Nonproductive cough, stridor, wheezing, dyspnea, orthopnea that worsens with recumbency or lying flat
• Syncope
• Patient may be asymptomatic and the mass incidentally found on CXR.

If lymphoma, find out if pretreated with steroids or radiation to shrink the tumor. The disadvantage of pretreatment is that it might affect tissue pathology (diagnosis).

• Bronchodilators
• Steroids, if part of a chemotherapeutic regimen

• Signs of SVC syndrome from compression
• Dynamic cardiac or airway compression with positional changes
• Parathyroid masses may be associated with hyperparathyroidism.
• Thymomas may have concurrent myasthenia gravis or immune deficiency.

• If the patient is a candidate to receive radiation or steroids to decrease the mass size
• If there is a potential for severe airway compromise, but a cardiopulmonary bypass (CPB) machine and perfusionist are not available

• Mediastinal masses are described based on their location relative to the heart:
  • Anterior: Teratomas, thyroid tumors, "terrible" lymphomas, thymomas (4Ts)
  • Middle: Lymph nodes, vascular masses
  • Posterior: Esophageal and neurogenic tumors, aneurysms

• Floor bed may be appropriate.
• ICU care may be needed depending on the intraoperative course.

• CBC to check for anemia
• for thoracic epidurals, the acute pain service should be contacted.

• Damage to the surrounding structures from procedure (e.g., phrenic and recurrent laryngeal nerve)
• Pneumothorax

• Mediastinoscopy
• Flow-Volume Loops
• Superior Vena Cava Syndrome
• Recurrent Laryngeal Nerve

519.3 Other diseases of mediastinum, not elsewhere classified

J98.5 Diseases of mediastinum, not elsewhere classified

Shital Vachhani , MD