Anesthesia for Patients with Mediastinal Masses
Patients with mediastinal masses can develop major airway and cardiovascular compression under general anesthesia, which could be fatal in nature. The key to management of these patients lies in early recognition of high-risk features and formulation of an anesthetic plan appropriate for the severity of symptoms. High-risk features include respiratory symptoms that are worsened in the supine position, such as orthopnea and increased cough, superior vena cava syndrome, pericardial effusion, and evidence of airway or cardiovascular compression on CT imaging. Knowledge of the anatomical location of the mass, as well as its relationship to vital cardiorespiratory structures, careful preoperative assessment, meticulous planning in conjunction with the surgeon, and preparation for possible perioperative complications are paramount in successful management of these patients. Diagnostic procedures should be performed under local anesthesia whenever feasible. If general anesthesia is required, induction should proceed in a stepwise fashion with confirmation of adequate ventilation and circulation before proceeding to the next step. Strategies for airway management include awake fiber-optic assessment of dynamic obstruction, intubation distal to airway compression, maintenance of spontaneous ventilation, and avoidance of muscle relaxation. Management of acute airway obstruction or cardiovascular collapse may include advancing tube beyond obstruction, repositioning patient, resumption of previously tolerated state, rigid bronchoscopy, and initiation of cardiopulmonary bypass (CPB) or extracorporeal membrane oxygenation (ECMO). Preinduction CPB and ECMO should be considered in extremely high-risk patients as rescue CPB may not be established rapidly enough in acute airway or cardiovascular collapse to prevent anoxic consequences.
KeywordsAirway obstruction Mediastinal mass Cardiovascular compression Positional Fiber-optic ECMO Cardiopulmonary bypass
Patients with mediastinal masses can develop major airway and cardiovascular compression under general anesthesia, which could be fatal.
High-risk features include supine symptoms (orthopnea, increased cough), SVC syndrome, pericardial effusion, and evidence of airway or cardiovascular compression on CT imaging.
Knowledge of the anatomical location of the mass as well as its relationship to vital cardiorespiratory structures should be obtained through imaging modalities.
Diagnostic procedures should be performed under local anesthesia whenever feasible.
Induction of general anesthesia should proceed in a stepwise fashion.
Airway management techniques may include awake fiber-optic assessment, intubation distal to airway compression, maintenance of spontaneous ventilation, and avoidance of muscle relaxation.
Perioperative planning should be made in conjunction with the surgical team, with inclusion of management plans for potential acute airway obstruction or cardiovascular collapse.
Preinduction CPB or ECMO cannulation should be considered in extremely high-risk patients.
Knowledge of mass anatomy, including its location and relationship to other vital structures (tracheobronchial tree, heart, major vessels), and knowledge of the pathophysiology of the mass
Careful preoperative assessment
Discussion and collaborative perioperative planning with surgeon
Preparation to manage cardiorespiratory complications
Surgical procedures encountered may include biopsy of extra-thoracic mass, biopsy of mediastinal mass via cervical mediastinoscopy, anterior parasternal mediastinoscopy/mediastinotomy (Chamberlain procedure), video-assisted thoracoscopic biopsy or excision of mass, thoracotomy, and sternotomy . These patients can also present for an unrelated surgical procedure (e.g., staging laparotomy) or be an incidental diagnosis at the time of another procedure [8, 9].
Anatomy and Pathophysiology
Masses in the mediastinal compartments
Thyroid (goiter, ectopic thyroid tissue)
Germ cell tumors (seminoma, teratoma, non-seminoma)
Cardiac/vascular structures (pericardial cysts, aneurysm)
Because of the proximity to other airway and cardiovascular structures, mediastinal masses can lead to complications under anesthetic due to compression or encroachment of these structures. Although the majority of complications are described for masses in the anterior mediastinum, masses in the middle mediastinum  and posterior mediastinum  have also been associated with hemodynamic and respiratory collapse with general anesthesia (GA).
During normal spontaneous ventilation, there is preferential perfusion to dependent areas of the lung and distribution of ventilation controlled mainly by lung compliance . Most studies evaluating ventilation changes under anesthesia have shown a decrease in functional reserve capacity (FRC) . With muscle paralysis and supine positioning, there is cephalad shift of the diaphragm that further contributes to impaired gas exchange under anesthesia. Neuman stated three reasons for the dangers of general anesthesia: (1) the reduction of lung volume by as much as 500–1500 ml under GA, (2) relaxation of bronchial smooth muscle leading to greater compressibility, and (3) loss of spontaneous diaphragmatic movement with paralysis, which reduces the normal transpleural pressure gradient that helps dilate the airways . These normal changes that occur under general anesthesia are especially pronounced in patients with mediastinal masses who may have limited reserve or further alteration of ventilation-perfusion matching due to extrinsic airway compression.
Induction of general anesthesia is a sequence of events, and complications can occur at any of these stages, including (1) changing patient position from upright to supine, (2) transitioning from awake to anesthetized state, (3) moving from spontaneous negative pressure ventilation to positive pressure ventilation, and (4) changing of muscle tone from unparalyzed to paralyzed state. Furthermore, complications do not occur solely at the time of induction and intubation but can extend into the maintenance phase, at extubation, or even into the postoperative period .
Numerous case studies documenting airway collapse [3, 6, 18] and cardiovascular collapse [5, 7, 18, 19] under anesthesia have been described. Most anesthetic deaths have been described in the pediatric population, possibly due to increased compressibility of pediatric airways or the lack of awareness of the extent of airway involvement [3, 4, 5], as well as the intolerance of any cardiovascular insult.
Hemodynamic decompensation may occur if there is compression of the heart or great vessels such as the pulmonary artery (PA) and superior vena cava (SVC). If the PA is compressed, decreased pulmonary perfusion can lead to hypoxemia, acute right ventricular dysfunction, and even cardiac arrest . Compression of SVC leads predominantly to a reduction in venous return and the subsequent reduction in cardiac output . Direct compression of the heart is rare but can lead to arrhythmias, pericardial effusion, or reduction in preload from mechanical compression .
Clinical Signs and Symptoms
Common symptoms include dyspnea, cough, hoarseness, new-onset wheezing, syncope, chest pain, night sweats, weight loss, dysphagia, and superior vena cava (SVC) obstruction [1, 17]. These symptoms are especially worrisome if it worsens in the supine position.
SVC syndrome can present with edema of the upper body (face, neck, larynx, upper limbs), plethora, dilation of veins (neck and thorax), and development of collateral veins if slowly evolving [11, 17, 20]. Patients can also present with CNS symptoms including headache, visual distortion, or altered mentation . Respiratory symptoms can accompany SVC obstruction due to concurrent compression of the airway by tumor or engorged veins .
Clinical signs may include tachypnea, stridor, rhonchi, or decreased breath sounds. Severity of respiratory symptoms may not correlate with degree of airway obstruction, especially in the pediatric population [6, 21, 22].
Coexisting systemic syndromes such as myasthenia gravis or thyroid dysfunction may be present, and their concurrent optimization needs to be considered, but the specific management of these conditions will not be discussed here.
Mediastinal masses may also be asymptomatic and found incidentally through work-up being performed for other indications. Occasionally these masses come to light due to perioperative complications for an unrelated surgical procedure, and patients are subsequently found to have a mediastinal mass [8, 9].
Following chest radiography, computed tomography (CT) is often the next choice of imaging modality as it can provide exact anatomical detail of the mass, including size and relation to adjacent structures [1, 23]. CT can provide useful information regarding the location and extent of airway compression, as well as cardiovascular involvement . Unfortunately, CT scans are static images that only assess one time-point and do not provide information about dynamic compression or position-related changes . MRI may provide more details regarding soft tissue but is not routinely performed. However, it may be useful for neurogenic and vascular lesions, especially when the use of contrast is contraindicated .
Azizkhan examined a series of 50 children with anterior mediastinal mass and found that the severity of pulmonary symptoms is not a reliable indicator of the degree of compression in children . Rather, those who had decreases in cross-sectional area of the trachea of at least 50% had the highest association of complications under general anesthetic. Retrospective analysis by Shamberger confirmed the absence of major complications in pediatric patients with a tracheal diameter greater than 50% predicted who underwent general anesthesia . A follow-up prospective study confirmed that GA was well tolerated in children with tracheal area and peak expired flow rate (PEFR) greater than 50% predicted. It was, however, unable to conclude whether impaired pulmonary function as measured by PEFR would be predictive of respiratory collapse during GA as the highest-risk patients were all operated on under local anesthesia .
Neuman et al. first advocated for pulmonary function testing and flow-volume loops in 1984, and it soon became widespread recommendation as part of the preoperative work-up of anterior mediastinal masses despite being based on anecdotal recommendations [16, 28]. Subsequent studies have failed to correlate degree of changes in spirometry with perioperative airway complication rates . Hnatiuk et al. assessed upright and supine spirometry and showed no correlation between abnormal spirometry results and respiratory symptoms, abnormal CT results, and anesthetic complications . Spirometry and flow-volume loops do not predict intraoperative morbidity and mortality beyond the information obtained on imaging studies [1, 28].
Transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) are indicated if clinical or CT information suggests cardiac or great vessel involvement. They provide additional information about encroachment or compression of cardiac structures . These exams can also be performed in recumbent and lateral positions to determine any positional changes in tumor compression effects . As some masses can enlarge and progress rapidly, imaging should be performed as close to the time of surgery as possible.
Other modalities that are sometimes employed include fluorodeoxyglucose positron emission tomography (FDG-PET), which may provide additional information for staging, diagnosis, and prognosis, as it evaluates the metabolic activity of the tumor to predict its response to neoadjuvant therapy .
An awake fiber-optic bronchoscopic exam assessing any dynamic airway compression, especially with positional changes, is a useful adjunct to preoperative evaluation and planning.
Risk Stratification (Fig. 14.2)
Preoperative high-risk criteria
Dyspnea when supine (orthopnea)
Increased cough when supine
Tracheal compression to <50% of predicted cross-sectional area (pediatric)
Neuman et al. presented a flowchart of suggested management of anterior mediastinal masses . Since then, there have been modifications on this flowchart with continued emphasis on maintaining spontaneous ventilation and avoidance of muscle relaxation if possible.
Knowledge and documentation of “position of comfort” for patient in terms of respiration and circulation may be useful .
Risk of complications in the pediatric population has been reported to be 7–20% [4, 25, 31, 32]. Bechard examined 105 anesthetics in the adult population and had an incidence of airway obstruction of 0% during the intraoperative period. However, some patients with the most worrisome features received preoperative chemotherapy or had their tissue biopsy obtained by other means . The overall intraoperative cardiorespiratory complication rate was 3.8%, and postoperative respiratory complication rate was 10.5% . This study found a correlation between the presence of cardiorespiratory symptoms and perioperative complications, with no perioperative complications seen in asymptomatic patients. Although an abnormal pulmonary function test (PEFR <40% predicted) did not predict intraoperative complications, it was associated with a tenfold increase in postoperative complications. Also, a combination of obstruction/restrictive pattern was also associated with a higher rate of postoperative complications .
Preoperative chemotherapy, steroids, or radiation therapy may reduce the size of the tumor and reduce intraoperative risk but may distort histological diagnosis. However, the recommendation of preoperative radiation may be warranted in cases of SVC syndrome as massive hemorrhage, respiratory obstruction, or fatal exacerbation of the SVC obstruction can occur with induction of general anesthesia .
Piro recommended preoperative radiation based on their series of 139 patients, where all 5 acute life-threatening complications were encountered in patients with untreated AMM . This recommendation is echoed by other authors [3, 18], while others [12, 31] feel that in the absence of tissue diagnosis, empiric treatment with radiation therapy may delay diagnosis or lead to inappropriate treatment of the mediastinal mass.
Tracheobronchial stenting can also be performed either via flexible or rigid bronchoscopy. This may provide a bridge to chemotherapy or radiation, used to maintain adequate airway prior to excision of mediastinal mass, or for palliation . Spontaneous ventilation maintained with the use of an LMA has been successfully described for placement of a self-expanding metallic stent . There is however a small chance that airway stenting may worsen patient hemodynamics by displacing the mass into adjacent cardiovascular structures.
The choice of anesthetic is based on preoperative risk stratification. For those with high-risk criteria (Table 14.2), the avoidance of general anesthesia and utilization of local or regional anesthesia is advocated if feasible, but this is less practical in the pediatric population.
The ability to rapidly change patient’s position should be considered prior to the initiation of anesthesia or surgery.
Judicious use (or avoidance) of sedation in the highest-risk population is recommended as respiratory depression, upper airway obstruction, and any amount of muscle relaxation may worsen compressive symptoms exerted by the mediastinal mass .
Dexmedetomidine has been used successfully in this population as a sole anesthetic without the use of muscle relaxant, with the ability to maintain spontaneous respirations with minimal respiratory depression .
Induction and Intubation
This should be performed in a stepwise approach, with verification of adequate ventilation and circulation at each step prior to proceeding [1, 17]. The use of short-acting medications allows for the resumption of the previously tolerated state (e.g., spontaneous ventilation).
No induction (local vs. regional, with or without sedation).
Awake fiber-optic intubation with placement of ETT beyond area of compression or stenosis; then proceed with induction.
Maintenance of spontaneous ventilation using small boluses of IV anesthetic (e.g., Ketamine , propofol, or etomidate) or inhalational induction.
Standard IV induction (with or without muscle relaxation).
Maintenance of spontaneous ventilation has been advocated. However, cases of airway collapse have also been documented despite maintenance of spontaneous respirations .
Prior to induction of anesthesia, alternative airway management and rescue for hemodynamic complications should be laid out. This may include long endotracheal tubes of varying diameters (e.g., endobronchial tubes, microlaryngeal tubes [MLT]), double-lumen tubes or bronchial blockers, flexible fiber-optic bronchoscope, rigid bronchoscope, (and an experienced bronchoscopist), and potential equipment and personnel to initiate extracorporeal circulation (ECC) if cannulation is planned prior to induction. Glycopyrrolate is useful in this population to reduce airway secretions prior to awake bronchoscopic airway assessments, as well as lessening any vagal responses to airway manipulation.
Muscle relaxation should be avoided whenever possible. If muscle relaxation is required for surgical reasons, a small dose of short-acting muscle relaxant such as succinylcholine should be given and mechanical ventilation attempted. If mechanical ventilation can proceed without any significant increase in airway pressure or hemodynamic compromise, subsequent doses of muscle relaxant can be considered .
The use of ECC including full cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO) in high-risk patients may be considered. This will be discussed in more detail below.
Maintenance of Anesthesia and Intraoperative Monitoring
Intraoperative transesophageal echocardiography (TEE) may play an increasing role during tumor resection, as it is an invaluable tool in the monitoring and diagnosis of hemodynamically unstable patients . It provides real-time imaging of the heart and nearby structures and can help establish anatomical and functional involvement of the tumor during resection [37, 38, 39, 40]. TEE can also provide information regarding contractility, degree of right ventricular outflow tract (RVOT) obstruction or compression , volume status, and presence of pericardial effusion [39, 41]. The American Society of Anesthesiologist and Society of Cardiovascular Anesthesiologists Task Force on Transesophageal Echocardiography supports the use of TEE in noncardiac surgical patients with known or suspected cardiovascular pathology that might result in hemodynamic, pulmonary, or neurologic compromise . Furthermore, its use should be considered in those with unexplained persistent hypotension as well as unexplained hypoxemia .
Emergence and Postoperative Care
Complications related to mediastinal masses have been reported in the postoperative periods; therefore increased vigilance must continue during this time. Transitioning from the anesthetized state to the awake state can pose an issue if pain, anxiety, or coughing leads to increased airflow and turbulence through a compromised airway . Tracheomalacia can occur with prolonged compression of airway by enlarging masses. Furthermore, upper airway obstruction and decreased muscle tone will further aggravate airway collapse during high inspiratory pressure exerted against a closed glottis. Patients with SVC obstruction may encounter post-extubation breathing issues due to airway edema .
Mediastinal mass syndrome (MMS) is a term describing the clinical picture caused by mediastinal mass in anesthetized patients, encompassing acute respiratory and hemodynamic decompensation .
Rescue options for airway obstruction
Rescue options for airway obstruction
Double-lumen tube or long endotracheal tube advanced beyond obstruction or compression 
Reposition patient to position of comfort (if known), lateral or prone (to decrease the weight of tumor on airway)
Resumption of previous tolerated state (e.g., upright position, spontaneous ventilation, awaken from anesthetic)
Rigid bronchoscopy beyond stenosis
Initiation of cardiopulmonary bypass or ECMO
Even asymptomatic patients can develop life-threatening obstruction at induction and maintenance of anesthetic [24, 37, 44]. Preoperative chest CT can provide accurate measurement of airway diameter, and it is important to determine the precise level and extension of compression [25, 44]. Any indication of tracheal or bronchial compression may be associated with airway complications under anesthetic.
Azizkhan et al. examined 50 consecutive cases of children with anterior mediastinal mass and found that all 5 cases of life-threatening complications occurred in those with tracheal compression >50% .
Spontaneous ventilation with the avoidance of muscle relaxant has often been advocated for this patient population, but this is not a failsafe option as airway collapse has been described in a case of anterior mediastinal mass despite spontaneous ventilation and avoidance of muscle relaxation .
Alternative airway management may include wire-reinforced endotracheal tubes, long endotracheal tubes, flexible fiber-optic bronchoscope, and rigid bronchoscope. Lee describes a case of airway obstruction on induction that was relieved with rigid bronchoscopy and subsequent placement of a double-lumen tube to act as an endobronchial stent .
Aggressive ventilation through a partially obstructed airway may lead to dynamic hyperinflation and worsened hemodynamics. These patients may benefit from transient disconnection from airway circuit or utilization of zero end-expiratory pressure (ZEEP).
Management of SVC syndrome
Management of SVC syndrome
Augmentation of preload
Positioning to minimize compression of heart or major vessels (e.g., lateral position)
Lower extremity IV access
Spontaneous ventilation to augment venous return
Sternotomy and lifting of mass to relieve compression
Compression of the pulmonary trunk or main pulmonary artery (PA) can also occur . Unlike the SVC, PA is relatively protected by the aortic arch, making it less vulnerable to external compression. If cyanosis does occur; the possibility of RVOT obstruction and subsequent hypoxemia, hypotension, or cardiac arrest should be considered [11, 19].
Extracorporeal Circulation (ECC)
Preinduction femoral cannulation for CPB can be considered in extremely high-risk patients as the use of CPB as an emergency rescue can take 10–20 min to initiate and can lead to anoxic brain injury [14, 28, 37]. Patient positioning, inadequate access to femoral vessels, and near-arrest conditions may further complicate vessel cannulation once the surgical procedure has commenced .
Femoral-femoral cardiopulmonary bypass (CPB) initiated in an awake patient under local anesthesia has been utilized in patients at high risk of airway or hemodynamic collapse with general anesthesia in which awake fiber-optic intubation may not always be feasible or successful [46, 47, 48, 49].
Increasingly, extracorporeal membrane oxygenation (ECMO) is being initiated prior to intubation as part of the airway plan in patients with mediastinal tumors with evidence of airway compromise [50, 51].
On the other hand, preinduction initiation of CPB carries with it the risks of anticoagulation and potentially unnecessary access to vessels. Occasionally, the patient may not tolerate attempts at awake cannulation, as they cannot endure supine positioning . Some authors have advocated for the placement of wires in femoral vessels without full commencement of CPB as a compromise .
Anesthesia for Mediastinoscopy
Mediastinoscopy can be performed for staging of lung cancer, for evaluation of mediastinal lymph nodes, or for obtaining tissues biopsy samples for diagnosis of mediastinal masses . The more common procedure is the cervical mediastinoscopy, where the mediastinoscope is inserted toward the carina through a small transverse incision in the suprasternal notch  and requires general anesthesia. The less commonly performed anterior mediastinoscopy is performed through the interchondral space along the second rib. This procedure can be performed under local anesthesia or general anesthesia while maintaining spontaneous respiration [54, 55], but coughing or movement can lead to catastrophic surgical complications.
The most significant immediate complication of mediastinoscopy is major hemorrhage. Adequate IV access in a lower extremity and availability of blood products should be considered. In a retrospective review of over 300 mediastinoscopies, Park et al. had a major hemorrhage rate of 0.4% . Ninety-three percent of the patients had control of hemorrhage through packing, and only one patient required emergency sternotomy. Once local tamponade was in place, all patients eventually underwent surgical exploration and management of bleeding. The most commonly injured vessels were the azygos vein and the innominate and pulmonary arteries . Lower limb IV access may be required if SVC injury is suspected. Principles of massive transfusion should be utilized until control of hemorrhage has occurred.
Pneumothorax is an uncommon complication but can lead to increased airway pressures, tracheal shift, hypotension, and cyanosis . Other rare complications include injury to the recurrent laryngeal nerve, which can cause vocal cord dysfunction, vagus nerve, and thoracic duct and compression of the aorta, which may lead to reflex bradycardia .
Improved understanding of the pathophysiology of mediastinal masses has improved the perioperative morbidity, and mortality has been reduced in this patient population. Careful preoperative assessment and knowledge of the location of the mass and its relationship to adjacent structures are paramount for anesthesia planning. Diagnostic procedures should be performed under local or regional anesthesia whenever possible. Close communication with the surgical team thorough risk assessment and devising a plan for intraoperative airway or hemodynamic complications all contribute to the successful management of these cases.
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