What the Anesthesiologist Should Know before the Operative Procedure

Mediastinal masses can be anterior, middle, or posterior in their location.

In general, anterior mediastinal masses (lymphomas, thymomas, germ cell tumors, metastatic lesions, and thyroid masses) are problematic due to compression of both airway and vascular structures. Middle (bronchogenic cysts, granulomas, and lymphomas) and posterior mediastinal masses (enteric cysts, duplications, neuroblastomas, neurofibromas, and ganglioneuromas) are not usually symptomatic from compression of anatomic structures. Clinical and radiologic exams will determine the potential risk for anesthesia.

Children are at a higher risk for anesthetic morbidity associated with anterior mediastinal masses. Orthopnea, great vessel compression, and pleural effusion are significant predictors of complications. If more than 50% tracheal compression is present preoperatively, a seven-fold increase in postoperative respiratory complications has been reported. Anesthesia-related major complications have been reported in the absence of preoperative respiratory symptoms in children, but this is not supported by larger case series of children.

Adults who present with severe cardiorespiratory symptoms may also experience complications related to anesthesia, although the incidence is not as high as in the pediatric population.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

There are two types of surgery: those to resect or biopsy the mass itself (usually intrathoracic procedures), and those in other locations (e.g., lymph node biopsy) with a mediastinal mass present.

2. Preoperative evaluation

The most serious complications will occur if there is airway or vascular compression by the mass.

Medically unstable conditions warranting further evaluation include: Patients presenting with symptoms of airway or CV compression.

All patients should have CXR and CT scan to evaluate the position of the mass relative to other mediastinal structures including the heart, great vessels and large airways.

MRI may aid in characterization of the mass by using differences in signal intensity to differentiate soft tissue from fat, fluid, or hemorrhage; not usually indicated. This might be helpful in posterior masses which are often neural in origin.

Delaying surgery may be indicated if: CT scan demonstrates a cross-sectional tracheal area less than 50% normal or if vascular structures are compressed. Consult with hematology-oncology to determine whether preoperative treatment of tumor is indicated. These are the patients at high risk for anesthetic airway complications.

If the patient has worrisome symptoms, other radiologic procedures may be performed under sedation or local anesthesia to get a diagnosis of the mass; see below.

Pulmonary function tests, specifically flow volume loops, or awake fiberoptic bronchoscopy may define the respiratory compromise but rely on both a cooperative patient and a skilled practitioner. These are not usually required.

An echocardiogram is recommended if the CT shows invasion or obstruction of vascular structures.

3. What are the implications of co-existing disease on perioperative care?

Cardiovascular system

Acute/unstable conditions: Symptoms of cardiovascular involvement by mass include syncope, chest pain, and dyspnea.

Symptoms include facial swelling, dyspnea, cough, arm swelling, orthopnea, pain, dysphagia, syncope, headache and stridor. Signs include dilated neck veins, facial swelling, prominent cutaneous veins, arms swelling, edema, cyanosis, and vocal cord paralysis. Superior vena cava syndrome may be present if the mass is compressing venous return. If CT scan demonstrates pericardial involvement or great vessel compression, an echocardiogram should be done. If a pericardial effusion is present, this predicts intraoperative hemodynamic instability. Risk reduction: Consider preoperative pericardial drainage or intraoperative cardiopulmonary bypass.Consult with CT service in advance. Extubation in the presence of SVC syndrome may be inadvisable. Intraoperative positioning that compounds the mass compression of great vessels (e.g., left lateral decubitus) should be avoided if possible.

Hemodynamic instability: Preoperative vital signs that demonstrate marked hypertension and tachycardia in the face of a posterior mediastinal mass may indicate a vasoactive neurogenic tumor. It may take several days for VMA results, depending upon your lab. If suspected, plan on invasive monitoring (arterial catheter, CVC) and have vasoactive drugs available.

Baseline coronary artery disease or cardiac dysfunction; a history of cardiac disease separate from the mediastinal mass should be elicited. If CAD or ventricular dysfunction is present, it should be optimized medically prior to surgery.

Pulmonary

Patients with symptoms of airway compromise such as dyspnea (especially postural), orthopnea, cough, or stridor should be assumed to have compression of the trachea or main bronchi by the mass. Preoperative evaluation includes:

i. CXR and CT are the minimal evaluation required. Tracheal cross section less than 50% predicted is associated with anesthetic complications especially in children.

ii. Awake fiberoptic bronchoscopy to evaluate compression is not usually indicated unless intubation is imminent (e.g., OR or ICU).

iii. Flow volume loops: flow decrease or plateau in the expiratory part of the curve suggests obstruction. This is not usually done

Risk reduction includes: avoidance of GA if possible when obstruction is present, spontaneous ventilation, avoidance of muscle relaxants, have rigid bronchoscope and other airway adjuncts in OR in case of airway obstruction.

Renal-GI:

N/A

Neurologic:

Acute issues: 10% of neurogenic tumors have extensions into the spinal column. Many of these tumors can cause spinal cord compression. Neuroblastomas are common posterior masses in children. They can cause hemodynamic instability due to catecholamine secretion. Risk reduction includes measuring VMA preoperatively if a posterior mass is present in children.

Endocrine:

If the anterior mass is a thymoma or intrathoracic goiter, thyroid function should be evaluated and treated if necessary.

Additional systems/conditions that may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Thymoma is the second most common mediastinal mass in adults and is associated with systemic syndromes caused by immunologic mechanisms including myasthenia gravis, red blood cell aplasia, aplastic anemia, Cushing syndrome, hypo- and hypergammaglobulinemia, SLE, rheumatoid, arthritis, and others.

4. What are the patient's medications and how should they be managed in the perioperative period?

N/A

Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Patients with cancer may have already undergone chemotherapy.
Corticosteroids may have been used preoperatively to shrink the tumor or treat the cancer; long-term use may indicate the need for a stress dose intraoperatively (1-2 mg/kg hydrocortisone IV in pediatric patient). If the patient is pre-chemotherapy, steroids may be contraindicated, as they can induce tumor-lysis syndrome.
Bleomycin is used for teratoma chemotherapy; patients may have residual effects on diffusion capacity, and a low inspired oxygen concentration should be used
Adriamycin/daunorubicin: can have long term effects on cardiac contractility even in the face of a normal resting echocardiogram

What should be recommended with regard to continuation of medications taken chronically?

Chronic medications can be taken assuming no contraindication exists (e.g., antiplatelet drugs with impending thoracotomy).

How to modify care for patients with known allergies

N/A

Latex allergy: If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

N/A

Does the patient have any antibiotic allergies?

N/A

Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia

Documented: Avoid all trigger agents such as succinylcholine and inhalational agents:

General anesthesia with spontaneous ventilation can be accomplished with propofol and other adjuvants such as ketamine, dexmedetomine, midazolam and judicious use of narcotics. Depending on the type of anesthesia machine and ventilator, high-flow oxygen should be used to flush the system preoperatively for at least 10 minutes (longer with newer machines/ventilators).
Ensure MH cart available.

Family history or risk factors for MH:

If MH history in first-degree relatives, avoid trigger agents. If distant relative has MH history or risk factor (e.g., muscle disorder), weigh the benefits vs risk of avoiding inhalation agents for the particular case.

Local anesthetics/ muscle relaxants:

Depending on the extent of mass effect, muscle relaxants may be relatively contraindicated. Avoidance of known allergens should be relatively easy to accomplish.

5. What laboratory tests should be obtained and has everything been reviewed?

If anterior mediastinal mass and critical airway or cardiac compression is present, other means of diagnosing tumor may be done to avoid surgery. These include:

a. Peripheral blood smear and flow cytology

b. Bone marrow aspirate

c. Pleural effusion thoracentesis

d. Image-guided needle biopsy of mediastinal mass or peripheral lymph node

These do not require general anesthesia, although sedation or local anesthesia may be indicated patient is a child.

Preoperative Evaluation (if surgery indicated for diagnosis or treatment)

Hemoglobin levels:

Patients who present with severe anemia secondary to cancer should be transfused to at least 7 g/dL, assuming no major coronary comorbidities.

Electrolytes:

Patients should have a baseline BUN and creatinine.

Coagulation panel:

Not necessary unless there is evidence of liver involvement or symptoms suggestive of bleeding dyscrasias

Imaging:

CXR and CT mandatory, and should be reviewed by the anesthesia team prior to performing an anesthetic. MRI is useful for posterior masses, which may be neurogenic in origin. Echocardiogram is indicated if CT demonstrates pericardial, cardiac, or great vessel involvement.

Special imaging:

Thyroid scan for suspected goiter or abnormal TFTs.

Other tests:

Posterior masses may represent neurogenic tumors, which could be vasoactive. Urinary VMAs would be indicated for diagnosis. Anti–acetylcholine receptor antibody (myastenic symptoms or mass contiguous with thymus)

Type and screen/cross:

Indicated for intrathoracic procedures to either biopsy or resect mass.

Intraoperative management: What are the options for anesthetic management and how to determine the best technique?

Ideally, patients with a symptomatic anterior mediastinal mass would avoid GA. The option to do sedation or regional depends on the age of the patient and the type of surgery.

Regional anesthesia

Depending upon the nature of the surgery, regional may be an option if the patient has a mediastinal mass. The benefits would be avoiding airway manipulation and relaxation of structures in those patients who are at highest risk (symptomatic anterior masses). The potential drawbacks would be the uncontrolled airway in the face of oversedation or failed intraoperative block.

General anesthesia

Benefits:

1. Children will likely need GA due to cooperation issues.

2. Adults will need GA for certain procedures that are not amenable to MAC or regional anesthesia.

Drawbacks: Most life-threatening complications occur under GA or after emergence from GA. Remember, both pulmonary and cardiac structures can be compressed!

1. Induction of GA reduces the thoracic diameter, inspiratory muscle tone is reduced, the diaphragm is upwardly displaced, and relaxation of the bronchial smooth muscles allows for further large airway compression.

2. Muscle relaxants cause loss of chest wall tone, and loss of airway tone due to spontaneous ventilation. This might precipitate the inability to manage the patient’s airway with a mask, and intubation beyond the compressing mass may be difficult.

Other issues:

The supine position for GA induction and/or surgery causes a reduction in the transverse diameter of the thorax and cephalad displacement of the diaphragm; this further exacerbates the airway compromise from the mass. Patients may do better in HOB upright position. Partial or full right lateral decubitus position may decompress the heart and great vessels if symptomatic obstruction occurs.
Cardiac encasement or great vessel involvement predicts perioperative complications.
Cardiopulmonary bypass has been recommended to “rescue” patients from cardiac arrest due to compression of the airways or great vessels after induction. If severe compression is expected, CV surgeons should be consulted about initiating CPB or cannulating femoral vessels for possible CPB before surgery. It is impractical to think that CPB will be initiated in a timely fashion after a cardiac arrest.
If SVC syndrome is present, IV access should be secured in lower extremities. If SVC syndrome is unrelieved by surgery, extubation may be difficult.

Airway concerns: As above. Supine position, positive pressure ventilation, and muscle relaxants can all contribute to airway compromise. Inhalation induction with partial airway obstruction may generate large negative intrathoracic pressures, flattening an already compressed trachea. Rigid bronchoscopes should be present in the OR if patient has significant airway compression preop. Long and/or reinforced endotracheal tubes are recommended to stent compressed trachea. Tracheobroncheal stents have been inserted by thoracic surgeons in adult patients who will require significant intrathoracic resection of the mass.

Monitored Anesthesia Care

Benefits: Avoids instrumentation of airway. Maintains spontaneous ventilation

Drawbacks: Depending on the surgery, may be technically difficult for surgeons and uncomfortable for the patient. If patient becomes overly sedated, positive pressure ventilation may be dangerous

Other issues: if bleeding occurs, conversion to GA may be required

6. What is the author's preferred method of anesthesia technique and why?

For mediastinal masses with minimal compression of airway and vascular structures and no signs/symptoms of cardiopulmonary compromise, general anesthesia can be performed without significant additional risk (low risk population).

Intermediate risk are those with mild postural symptoms and a tracheal compression <50%. High risk are those patients with significant postural symptoms, tracheal compression >50%, and/or compression of heart or great vessels.

Intermediate or high risk may require a semi-Fowler position for sedation or induction of GA. Sedation in children can be difficult, as airway obstruction due to oversedation may lead to unwanted positive pressure ventilation and subsequent complications. Sedative/analgesics such as ketamine and dexmedetomidine may be advantageous in maintaining spontaneous ventilation.

If GA is required in intermediate or high risk patients, I perform inhalation induction with maintenance of spontaneous ventilation, sometimes in the sitting position. A rigid bronchoscope (and someone who can use it) is available. For intubation, I topicalize the trachea with 2% lidocaine and intubate under “deep” GA with a reinforced endotracheal tube that will go distal to the obstruction.

For adults with significant airway compromise, awake fiberoptic intubation after good airway topicalization allows evaluation of the area of obstruction and a secure airway prior to induction. If hypotension occurs, consider changing position to move mass off vascular structures (e.g., right lateral decubitus). If spontaneous ventilation is not feasible, controlled ventilation may be done, but muscle relaxants are avoided. Patients are extubated awake.

What prophylactic antibiotics should be administered?

For cardiac or vascular procedures (e.g., chest cases, central venous access), cefazolin (2-3 g adults, 25 mg/kg pediatrics) or vancomycin (1 g IV adults, 10 mg/kg pediatrics). If patient is allergic to beta-lactam antibiotics, vancomycin or clindamycin (600 mg adults, 10 mg/kg pediatrics) is acceptable (SCIP recommendations).

What do I need to know about the surgical technique to optimize my anesthetic care?

If one-lung ventilation will be needed, a double-lumen ETT or bronchial blocker may be required. If a bone marrow biopsy will be done as part of the procedure, the prone positioning needs to be considered in the airway management.

What can I do intraoperatively to assist the surgeon and optimize patient care?

Communication regarding difficulties with ventilation and hemodynamics are imperative. If the patient is awake but sedated, good local anesthesia will be needed from the surgeons. Additionally, the semi-Fowler position may be required, which may be technically more difficult for surgeons to access neck structures.

What are the most common intraoperative complications and how can they be avoided/treated?

Airway obstruction: Avoid paralysis and positive pressure ventilation. Intubate with an ETT that goes distal to airway compression. Extubate awake. Consider leaving patient intubated postoperatively if SVC syndrome is still present.
Cardiovascular: Hypotension or cardiac arrest: likely this is related to compression of great vessels by the mass. Immediately change position to upright, lateral, or prone; supine may represent the worst scenario for compression.
Neurologic: Intrathoracic injury to the phrenic or recurrent laryngeal nerve may compromise ventilatory effort postoperatively.

If the patient is intubated, are there any special criteria for extubation?

If the patient has significant head and neck edema (SVC syndrome), extubation may not be safe until resolution after treatment of the underlying condition. Additionally, patients who were marginally ventilating preoperatively due to compression of the airways may require continued airway intervention until the mass is somewhat smaller.

Postoperative management

What analgesic modalities can I implement?

If a thoracotomy has been done, epidural analgesia and paravertebral blocks have been demonstrated to provide adequate postoperative pain control. Conventional opioid therapy can also be used.

What level bed acuity is appropriate?

Depending on the type of surgery and the degree of obstruction related to the mediastinal mass, an ICU bed may be indicated.

What are common postoperative complications, and ways to prevent and treat them?

Usually, surgeries have been performed for diagnostic reasons, and the underlying condition has yet to be treated. Therefore, expect that surgery and anesthesia may provoke additional problems. In one study, two-thirds of all complications occurred in the postoperative period. These included pneumonia, airway edema, and atelectasis. Avoidance of airway manipulation if possible, and judicious extubation in those who have airway edema may prevent these issues.

What's the Evidence?

Anghelescu, DL, Burgoyne, LL, Liu, T, Li, C, Pui, C, Hudson, M, Furman, W, Sandlund, JT. “Clinical and diagnostic imaging findings predict anesthetic complications in children presenting with malignant mediastinal masses”. Pediatr Anesth. vol. 17. 2007. pp. 1090-8.

Bechard, P, Letourneau, L, Lacasse, Y, Cote, D, Bussieres, J. “Perioperative cardiorespiratory complications in adults with mediastinal mass: incidence and risk factors”. Anesthesiology. vol. 100. 2004. pp. 826-34.

Blank, RS, de Souza, DG. “Anesthetic management of patients with an anterior mediastinal mass: continuing educational development”. Can J Anaesth. vol. 58. 2011. pp. 860-7.

Erdos, G, Tzanova, I. “Perioperative anaesthetic management of mediastinal mass in adults”. Eur J Anaesthesiol. vol. 26. 2009. pp. 627-32.

Gothard, JW. “Anesthetic considerations for patients with anterior mediastinal masses”. Anesthesiol Clin. vol. 26. 2008. pp. 305-14.

Hack, HA, Wright, NB, Wynn, RF. “The anesthetic management of children with anterior mediastinal masses”. Anaesthesia. vol. 63. 2008. pp. 837-46.

Stricker, PA, Gurnaney, HG, Litman, RS. “Anesthetic management of children with an anterior mediastinal mass”. J Clin Anesth. vol. 22. 2010. pp. 159-63.

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