Abstract
This chapter discusses the signs, symptoms, diagnostic work up and anesthetic consideration related to children with anterior mediastinal masses.
A 16-year-old female presents for a diagnostic biopsy of a cervical lymph node and central venous port placement. She had been previously healthy until several weeks prior to admission, when she was noted to have cervical and supraclavicular lymphadenopathy, facial plethora, and occasional stabbing chest pains. On examination, HR = 110 beats/min, RR = 32 breaths/min. Orthopnea is present except when her head is elevated to > 30°. Laboratory testing is significant for a WBC of 63,000 per microliter, of which 57% were blast cells. An electrocardiogram demonstrates electrical alternans. The AP chest radiograph shows an enlarged mediastinum and right pleural effusion.
What Are the Different Compartments of the Mediastinum?
The mediastinum can be divided into superior and inferior compartments, and the inferior compartment consists of the anterior, middle, and posterior sections. There is no actual anatomic separation between these compartments; however, on chest radiographs (Figure 19.1), the compartments can be delineated as:
The superior mediastinum is an area that is bound by the thoracic inlet superiorly, the thoracic place inferiorly, the mediastinal pleura laterally, the manubrium anteriorly and the bodies of the upper four thoracic vertebrae posteriorly;
The inferior mediastinum is subdivided into anterior, middle, and posterior sections:
The anterior mediastinum lies between the sternum and pericardium.
The middle mediastinum contains the pericardium, heart, ascending aorta, lower half of superior vena cava, trachea, main bronchi, pulmonary artery, pulmonary vein, and phrenic nerve.
The posterior mediastinum is located between the pericardium and the vertebral column.
Figure 19.1 Lateral chest radiograph highlighting the anterior (AM), middle (MM), and posterior mediastinal (PM) compartments.
What Is the Differential Diagnosis of an Anterior Mediastinal Mass?
While pathologies can occur in any mediastinal region and cross over to adjacent areas, it is pathology in the anterior mediastinum that is most associated with perioperative risk. Leukemias (especially T-cell) and lymphomas (Hodgkin’s and non-Hodgkin’s) have a predilection for the anterior mediastinum. Although thymomas and germ cell tumors with anterior mediastinal involvement may also occur in children, most anterior mediastinal masses will occur in adolescents and will likely be a type of lymphoma.
What Are the Symptoms Associated with Anterior Mediastinal Masses?
Signs and symptoms associated with anterior mediastinal masses can be divided into those related to the airway, cardiac, and vascular systems, as well as constitutional symptoms. Respiratory and cardiovascular symptoms may be dependent on the patient’s position, such that lying supine may increase pressure of the mass on the trachea and cardiac structures.
Airway/Respiratory Symptoms
Inspiratory stridor
Dyspnea
Nonproductive cough
Hoarseness (due to recurrent laryngeal nerve involvement)
Orthopnea (symptoms worsen with supine position due to tracheal compression)
Tracheomalacia (weakened tracheal walls) caused by prolonged tumor compression
Decreased breath sounds
Expiratory wheeze
Cardiovascular Signs and Symptoms
Syncope
Tachycardia
Plethoric facies (vascular compression): SVC syndrome
Cyanosis
Pleural effusion due to impaired lymphatic drainage
Paradoxical decrease in blood pressure occurs when going from upright to supine. This is due to obstructed right ventricular filling or ejection
Pericardial effusion
Cardiac tamponade
Constitutional (“B Symptoms”)
Fever, chills
Night sweats
Weight loss
The most significant risk factors predisposing patients to anesthetic complications include:
What Are the Anesthetic Risks of an Anterior Mediastinal Mass?
An anterior mediastinal mass may grow so large that it causes tracheal and/or bronchial compression. Compression of the superior vena cava or right atrium may lead to obstruction of blood flow into (superior vena cava syndrome) or out of the heart. When this obstruction is severe, the negative intrathoracic pressure generated by spontaneous ventilation precariously maintains the patency of the lower airway and great vessels and is often made worse when the patient is in the supine position (i.e., orthopnea). Administration of sedatives or anesthetic agents may result in potentially life threatening airway obstruction and great vessel compression. This obstruction cannot always be overcome by administration of positive-pressure ventilation.
In one notable case from 1981, a 9-yr-old boy with a known anterior mediastinal mass developed cardiac arrest and died during inhalational induction with halothane in the sitting position despite initially breathing spontaneously. Although the child was easily intubated and ventilated, he developed asystole that was unresponsive to all resuscitative efforts. The history revealed that four days prior to the procedure, the child became cyanotic and lost consciousness while straining during a bowel movement. An autopsy revealed that a large lymphoma had enveloped the heart and pulmonary artery, but in 1981, preoperative echocardiograms were not yet standard of care for these diagnoses. If this large mass surrounding the heart had been revealed prior to the procedure, perhaps the team might have chosen a less sedating technique. This is only one of many similarly reported cases of children with anterior mediastinal masses who have succumbed during administration of general anesthesia.
What Preoperative Diagnostic Studies Should Be Performed in a Patient with an Anterior Mediastinal Mass?
Preoperative evaluation should focus on identification of risk factors associated with anesthetic complications, specifically airway collapse and cardiovascular compromise. A CT scan of the chest will delineate airway and cardiopulmonary involvement (Figure 19.2), and an ECG and echocardiogram will reveal the extent of cardiovascular compression from the mass. Pulmonary function tests have not proven predictive of poor outcomes and will delay intervention, and thus, are not indicated.
Figure 19.2 CT scan demonstrating significant tracheal compression, pericardial effusion, SVC compression, and aortic encasement. This can be compared with Figure 19.3, an AP chest X-ray from the same patient.
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