Friday, March 19, 2021

Anterior Mediastinal Mass Case File

Posted By: Medical Group - 3/19/2021 Post Author : Medical Group Post Date : Friday, March 19, 2021 Post Time : 3/19/2021
Anterior Mediastinal Mass Case File
Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 27
A 29-year-old man presented to the hospital with a 5-week history of fatigue, nonproductive cough, increasing dyspnea, and pleuritic chest pain. He had no history of hemoptysis, night sweats, or fevers, and his medical history was otherwise unremarkable. On physical examination, the patient was noted to be tachypneic and dyspneic at rest, with seemingly prolonged expiration and accessory muscle use. His blood pressure was 116/71 mm Hg, the pulse 74 bpm, the respiratory rate 18 breaths per minute, the temperature 36.3°C, and the oxygen saturation 88% while the patient was breathing room air. On auscultation of the chest, breath sounds were normal. Blood chemistry and hematology values were all normal, except for hypoxemia and a mild respiratory alkalosis (partial pressure of oxygen [PO2] = 53 mm Hg, arterial oxygen saturation [SaO2] = 86%, partial pressure of carbon dioxide [PCO2] = 30 mm Hg, and pH = 7.48; fraction of inspired oxygen [FiO2] = 1). A chest radiograph showed a small left pleural effusion with a large mass in the anterior and middle mediastinum abutting the heart and hilar structures. Subsequent computed tomographic examination showed a mass in the anterior mediastinum measuring 12.3 × 5.6 × 11 cm. It compressed the tracheobronchial tree posteriorly.

➤ What are the most serious outcomes in patients with a mediastinal mass?

➤ How can the risk of these complications be reduced?

➤ What is the optimal anesthetic plan?


ANSWERS TO CASE 27:
Anterior Mediastinal Mass

Summary: A 29-year-old man with a symptomatic anterior mediastinal mass undergoing diagnostic mediastinoscopy.

Most serious outcome: Airway obstruction and hemodynamic instability including cardiac arrest, especially with the administration of general anesthesia in patients with anterior mediastinal masses. Although the possibility for a disastrous outcome still exists, improvements in the intraoperative management of these cases have rendered severe intraoperative respiratory or cardiovascular collapse less likely. Major life-threatening complications now occur more frequently postoperatively.

Minimizing risks: The primary goal during general anesthesia is the maintenance of spontaneous ventilation if at all possible. Positioning the patient either sitting and leaning forward at a 45 degree angle, or moving from supine to lateral or prone may help prevent cardiovascular or respiratory collapse. Cardiopulmonary bypass may also be indicated.

Anesthesia plan: Preoperative studies (CT, transthoracic echocardiography) determine the structural abnormalities and facilitate coordinated planning between the anesthesia and surgical teams. Local anesthesia with sedation, regional anesthesia, or general anesthesia with the maintenance of spontaneous ventilation represent appropriate anesthetic options. Of course, it is imperative to monitor gas exchange and hemodynamics while maintaining spontaneous ventilation until either the airway is definitively secured or the procedure is completed.


ANALYSIS

Objectives
1. Understand the complications, including respiratory and cardiovascular collapse, including the inability to resuscitate, that can ensue on induction of general anesthesia.
2. Become acquainted with the technique for extubating a patient with a mediastinal mass.
3. Examine what have been identified as suitable methods to care for this group of patients.


Considerations
In this patient with a mediastinal mass, monitoring during surgery includes a continuous two-lead electrocardiogram (lead II and V5), oxygen saturation, and direct arterial pressure catheter. Anesthesia is induced with an inhalational agent such as sevoflurane, with the patient sitting at a 45 degree angle and breathing spontaneously. In contrast, an induction with intravenous agents could well be associated with apnea. Respiration can be assisted if necessary, but tracheal intubation is achieved without the use of neuromuscular blockade.

Consistent with the CT scan, fiberoptic bronchoscopy will likely reveal a severe (> 70%) compression of the lumen of the lower third of the trachea. If possible, the end tracheal tube is advanced distal to the tracheal compression under fiberoptic guidance. This will allow ventilation of both lungs, and subsequent bronchoscopic examination. An uncomplicated left anterior mediastinoscopy revealed a high-grade Hodgkin lymphoma at biopsy. The conclusion of the procedure, the patient was successfully extubated awake, while again, sitting at a 45 degree angle.

APPROACH TO
Anterior Mediastinal Mass

Anesthesia in patients with anterior mediastinal masses has been associated with airway obstruction and hemodynamic instability, including cardiac arrest. However, due to the increased awareness by the medical community of the significance of this syndrome, there has been a significant decline in intraoperative fatalities during general anesthesia. Major airway complications in these patients are now more likely to occur in the PACU, instead of the operating room.

Since an anterior mediastinal masses vary in anatomy, pathology, and the proposed surgical procedure, there is the need to individualize management for each patient. Masses may be benign or malignant tumors, cysts, or aneurysms, and may originate from the lung, pleura, or any of the components of the anterior mediastinum. Etiologies include (in order of frequency): lymphoma (Hodgkin or non-Hodgkin), thymoma, germ cell tumor, granuloma, bronchogenic carcinoma, thyroid tumors, bronchogenic cyst, and cystic hygroma. Possible diagnostic or therapeutic surgical procedures include sternotomy, thoracotomy, cervical mediastinoscopy, anterior parasternal mediastinoscopy, or video-assisted thoracoscopic biopsy.

Patients typically present with signs or symptoms that include chest pain, dyspnea, cough, sweats, superior vena cava obstruction, hoarseness, syncope, or dysphagia. Patients may also be asymptomatic, and have a mass diagnosed on screening chest radiograph or computed tomography (CT) scan. Signs and symptoms which should alert the anesthesiologist to the possibility of an increased risk of airway complications are increased dyspnea, orthopnea, or cough when supine. An increased risk of cardiovascular collapse is suggested by syncopal symptoms or pericardial effusion. Patients with severe symptoms cannot voluntarily lie supine even for a short duration. Similarly, placing them in the supine position following the induction of anesthesia can have disastrous consequences.

The preoperative preparation of the patient with an anterior mediastinal mass includes a chest radiograph and a CT scan prior to any surgical procedure. In addition, the anesthesiologist must personally examine the imaging studies to plan the airway management. The CT scan will show the site, severity, and extent of the airway compromise. In patients who are unable to tolerate the supine position due to the compressive effects of the mass, the scan can be performed in either prone or lateral position. Patients with cardiovascular symptoms should also have transthoracic echocardiography to assess for cardiovascular compromise. Flow-volume loop studies have not been shown to be of benefit in the perioperative assessment or management of these patients.

The intraoperative administration of anesthesia for patients requires careful planning and execution to maintain airway patency and patient safety. It is imperative to monitor gas exchange and hemodynamics while maintaining spontaneous ventilation until either the airway is definitively secured or the procedure is completed. Induction is best achieved with a volatile agent such as sevoflurane by a slow, intravenous titration of propofol to ensure that apnea does not ensue, and possibly with the addition of ketamine. Alternatively, dexmedetomidine may also be a useful adjunct. Intubation of the conscious patient prior to induction is also a practical approach in some patients. If muscle relaxants are required, assisted ventilation should first be gradually taken over manually to assure that positivepressure ventilation is tolerated and only then can a short-acting muscle relaxant be administered.

The development of airway or vascular compression requires that the patient be awakened as rapidly as possible and other options for surgery implemented. If intraoperative airway compression occurs, possible remedies include changing the patient’s position from supine to lateral or prone, or by passing a rigid bronchoscope distal to the obstruction. Lastly, in severely compromised patients who cannot tolerate general anesthesia, cannulation of the groin for the use in cardiopulmonary bypass should be performed preemptively. In some cases, it may also be appropriate to begin cardiopulmonary bypass electively, and not just to be ready in a standby mode.


Comprehension Questions

27.1. Patients with positional dyspnea exacerbated by laying supine warrant which of the following preoperative assessments before a surgical procedure?
A. A CT of the chest
B. An ENT consult
C. Pulmonary function studies—flow volume loops
D. Pulmonary function studies—response to bronchodilators

27.2. Safe anesthetic care for a patient with a symptomatic anterior mediastinal mass includes which of the following?
A. Induction with propofol and succinylcholine followed by laryngoscopy and endotracheal intubation.
B. Positioning the patient supine.
C. Maintaining controlled ventilation and PEEP at all times.
D. Preoperative discussion with the surgeon about the radiologic imaging studies, perioperative plan, and contingency options which may include cardiopulmonary bypass.


ANSWERS
27.1. A. Patients with positional dyspnea exacerbated by lying supine warrant a physical examination of their head and lungs, a CT scan of the chest, and a chest radiograph before a surgical procedure. Pulmonary function studies including flow-volume loops or the response to bronchodilators are not helpful in predicting possible compression of the airway. If these tests are normal, then an ENT consult to examine possible pharyngeal or tracheal pathology would be indicated.

27.2. D. Safe anesthetic care for a patient with a symptomatic anterior mediastinal mass includes maintaining spontaneous ventilation and airway patency at all times, positioning the patient in a sitting or upright position, and preoperative discussion with the surgeon about the radiologic imaging studies, formulation of a perioperative plan, and contingency options which may include cardiopulmonary bypass. Answer A, bolus intravenous propofol and succinylcholine followed by laryngoscopy and endotracheal intubation is contraindicated in patients with a mediastinal mass unless cardiopulmonary bypass has been instituted.


Clinical Pearls
➤ Anesthesia in patients with anterior mediastinal masses has been associated with airway obstruction and hemodynamic instability including cardiac arrest.
➤ Maintenance of spontaneous ventilation is the anesthetic goal whenever possible.
➤ Major life-threatening complications now occur more frequently postoperatively.

References

Current Opinion in Anesthesiology. 2007;20:1-3.

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