Large mediastinal masses can result in the following:
1. Airway compression, causing dyspnea, which is aggravated in the supine position.
2. Encasement of the heart by a tumor, causing a hemodynamic effect similar to pericardial tamponade. The fixed, low cardiac output is aggravated by the following:
a. Supine position (further compression by tumor)
b. Straining at stool (Valsalva maneuver)
c. Myocardial depressant effects of general anesthesia d. Induction of anesthesia, which may result in collapse of the trachea by the tumor and complete airway occlusion if the action of the voluntary respiratory muscles is paralyzed (decrease in intrathoracic negative pressure).
The preoperative assessment of patients with mediastinal masses, particularly those who are symptomatic (dyspnea, intolerance of supine position), should include studies to assess airway patency and cardiac status. These studies should include:
1. Chest radiograph, including posteroanterior and lateral views for evidence of airway compression. High-kilovolt-magnified radiographs of the airway and/or CT scans of the chest should be performed to assess the status of the patency of the trachea.
5. Pulmonary function studies in upright and supine positions. If there is any evidence of cardiac or airway impairment, local anesthesia in the sitting position for cervical node biopsy should be carried out.
In children with large mediastinal masses in which general anesthesia is obligatory, endotracheal intubation or tracheostomy may not suffice to relieve the obstruction. In these cases, a system that will independently ventilate each lung beyond the sites of obstruction is needed.
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