UBP 1.4 (Short Form): Pulmonary – Mediastinal Mass

Question 1

What do you think may be causing her shortness of breath?

(A 36-year-old female presents for biopsy of an anterior mediastinal mass. Her medical history is significant for Down’s syndrome, moderate to severe asthma, and severe gastroesophageal reflux. Her mother states that her daughter is a smoker, gets short of breath at times, and sometimes has difficulty swallowing. The patient is a poor historian and was minimally cooperative during intravenous line placement. She takes Tums. VS: P = 87, BP = 110/70 mmHg, R = 12, T = 36.6 °C)

Answer 1

Given her history, her shortness of breath could be secondary to:

1. mass compression of the airways;
2. mass compression of the heart or great vessels (i.e. direct cardiac compression, pericardial effusion, superior vena cava syndrome, pulmonary artery compression);
3. aspiration (secondary to her severe GERD, which is likely undertreated, and/or dysphagia);
4. asthma;
5. COPD from smoking; or
6. myasthenia gravis, an autoimmune disease that can lead to dysphagia through direct effects on the heart or respiratory muscle weakness. (myasthenia gravis is associated with thymoma, a common anterior mediastinal mass).

Xtra Q – How would you determine what is causing her shortness of breath?

A focused history and physical exam along with a review of her CT scan, CXR, PFTs (helps to see if her shortness of breath improves with bronchodilator therapy), and echocardiogram would be helpful in identifying airway and/or cardiac compression or signs of COPD.

Besides dyspnea, myasthenia gravis is associated with diplopia (causing blurred vision), ptosis, dysphagia (difficulty swallowing), difficulty chewing, dysarthria (i.e. slurred speech), and muscle weakness.

This autoimmune disease can be diagnosed with –

• a tensilon test (first line diagnostic test),
• nerve stimulation, or
• antibody immunoassays.

Finally, a targeted history and physical focusing on the severity, course, and response to treatment of her GERD and asthma would aid in determining the degree that these medical conditions were contributing to her shortness of breath.

Question 2

Could her shortness of breath be due to myasthenia gravis?

(A 36-year-old female presents for biopsy of an anterior mediastinal mass. Her medical history is significant for Down’s syndrome, moderate to severe asthma, and severe gastroesophageal reflux. Her mother states that her daughter is a smoker, gets short of breath at times, and sometimes has difficulty swallowing. The patient is a poor historian and was minimally cooperative during intravenous line placement. She takes Tums. VS: P = 87, BP = 110/70 mmHg, R = 12, T = 36.6 °C)

Answer 2

The respiratory muscle compromise associated with myasthenia gravis could certainly be causing or contributing to her shortness of breath.

Thymoma is one of the most common anterior mediastinal masses and a significant number of patients with thymoma develop myasthenia gravis (30-65%).

Moreover, while her difficulty swallowing may be secondary to mass compression, it could also represent bulbar symptomatology often associated with myasthenia gravis.

If after further examination I were concerned about myasthenia gravis, I would consult a neurologist for definitive diagnosis and treatment.

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• Clinical Note:*
• Bulbar symptomatology refers to weakness in the muscles innervated by cranial nerves V, VII, and IX-XII. The result is facial weakness, difficulty chewing, dysphagia, and dysarthria.
• –*
• Xtra Q – What is myasthenic syndrome? (opportunity to demonstrate more knowledge… go ahead and be quick and offer more info such as myasthinc syndrome vs. myasthenia gravis)*
• –*
• Xtra Q – How is myasthenic syndrome treated? How does 3,4 diaminopyridine help? (~8:15 “Commentary on Stem & Pre-op”)*

Question 3

What is the pathophysiology of myasthenia gravis?

(A 36-year-old female presents for biopsy of an anterior mediastinal mass. Her medical history is significant for Down’s syndrome, moderate to severe asthma, and severe gastroesophageal reflux. Her mother states that her daughter is a smoker, gets short of breath at times, and sometimes has difficulty swallowing. The patient is a poor historian and was minimally cooperative during intravenous line placement. She takes Tums. VS: P = 87, BP = 110/70 mmHg, R = 12, T = 36.6 °C)

Answer 3

Myasthenia gravis is an autoimmune disorder that leads to the destruction of nicotinic acetylcholine receptors.

The reduction of these receptors at the neuromuscular junction, along with a reduced number and depth of the junctional folds in the postsynaptic membrane, results in muscle weakness, especially affecting those muscles of the eyes, face, throat, neck, and limbs.

This weakness, which worsens with activity and improves with rest, leads to diplopia (causing blurred vision), ptosis (drooping eyelids), dysphagia (difficulty swallowing), difficulty chewing, dysarthria (i.e. slurred speech), and dyspnea (with respiratory muscle involvement).

The disorder can also affect the heart, leading to mild hypertension, first-degree atrioventricular block, atrial fibrillation, myocarditis, cardiomyopathy, diastolic dysfunction, and dyspnea.

Finally, myasthenia gravis is associated with hyperthyroidism (10% of patients), rheumatoid arthritis, pernicious anemia, systemic lupus erythematosus, and transient skeletal muscle weakness in 15% of neonates born to mothers with the disorder (the weakness lasts for 2-4 weeks).

Question 4

With further questioning, the patient reports that she becomes lightheaded when lying on her back. Does this concern you?

(A 36-year-old female presents for biopsy of an anterior mediastinal mass. Her medical history is significant for Down’s syndrome, moderate to severe asthma, and severe gastroesophageal reflux. Her mother states that her daughter is a smoker, gets short of breath at times, and sometimes has difficulty swallowing. The patient is a poor historian and was minimally cooperative during intravenous line placement. She takes Tums. VS: P = 87, BP = 110/70 mmHg, R = 12, T = 36.6 °C)

Answer 4

This is very concerning because, in the setting of an anterior mediastinal mass,

a history of presyncope with supine positioning is associated with an increased perioperative risk of cardiovascular collapse.

Her positional syncope is likely the result of mass compression of the heart, superior vena cava, or pulmonary artery, all of which increase the risk for complete cardiovascular collapse during the perioperative period.

I would also keep in mind that there are other potential cardiac manifestations of myasthenia gravis that could be contributory (e.g. mild hypertension, first degree AV block, atrial fibrillation, myocarditis, and diastolic dysfunction).

Therefore, I would –

• examine the patient and review a recent chest x-ray, CT scan, echocardiogram, and any other available information (e.g. pulmonary function tests or angiogram – the latter is sometimes utilized to evaluate great vessel involvement) to evaluate any mass involvement of the heart or great vessels and to identify any additional risk factors for perioperative cardiopulmonary complications, such as:
  
  1. tracheal compression > 50%,
  2. tracheal compression > 30% in combination with bronchial compression,
  3. stridor,
  4. orthopnea,
  5. cyanosis,
  6. jugular distention,
  7. superior vena cava syndrome,
  8. pericardial effusion,
  9. pleural effusion, and
  10. a combined obstructive and restrictive pattern on pulmonary function tests.

Clinical Notes:

• Compression of the heart can cause similar symptoms to restrictive pericardial disease or cardiac tamponade, either directly by tumor compression or indirectly by causing a reactive pericardial effusion.
• A diagram of the mediastinum (see Figure attached)

Question 5

The CT scan shows 50% tracheal compression by the mediastinal mass.

Does this concern you?

(A 36-year-old female presents for biopsy of an anterior mediastinal mass. Her medical history is significant for Down’s syndrome, moderate to severe asthma, and severe gastroesophageal reflux. Her mother states that her daughter is a smoker, gets short of breath at times, and sometimes has difficulty swallowing. The patient is a poor historian and was minimally cooperative during intravenous line placement. She takes Tums. VS: P = 87, BP = 110/70 mmHg, R = 12, T = 36.6 °C)

Answer 5

This is concerning because this degree of tracheal compression is associated with an increased risk of complete airway collapse.

This finding, along with her shortness of breath, presyncope in the supine position, and the potential presence of subglottic tracheal stenosis associated with her Down’s syndrome, is very concerning due to the substantial risk of perioperative airway compromise.

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Chronic compression or tumor invasion of the tracheobronchial tree can affect the structural integrity of the trachea, making it more susceptible to collapse with –

1. direct mass compression,
2. forced expiration (positive intrathoracic pressure), and with
3. increased negative intraluminal pressures, such as may occur with spontaneous ventilation in the presence of a partial airway obstruction proximal to the structurally affected segment (e.g. subglottic tracheal stenosis).

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Xtra Q – Why do you care how far in the thorax the mediastinal mass goes?

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Given these concerns, I would –

• review all available imaging to identify the level of airway compression, recognizing that airway compression below the level of the carina may further increase her risk by making passage of an endotracheal tube or bronchoscope beyond the area of compression more difficult or impossible.

Moreover, I would –

• evaluate the patient for symptoms of airway compression, such as dyspnea, tachypnea, and wheezing (recognizing that any of these could result secondary to her asthma or advanced COPD secondary to tobacco use), and
• attempt to ascertain whether these symptoms were exacerbated by supine positioning.

Finally, I would –

• have a discussion with the surgeon about the benefits of performing the procedure under local anesthesia and/or attempting to reduce the size of the tumor with chemotherapy, radiation, or steroid administration prior to proceeding with the case.

Question 6

Would you order an echocardiogram?

(A 36-year-old female presents for biopsy of an anterior mediastinal mass. Her medical history is significant for Down’s syndrome, moderate to severe asthma, and severe gastroesophageal reflux. Her mother states that her daughter is a smoker, gets short of breath at times, and sometimes has difficulty swallowing. The patient is a poor historian and was minimally cooperative during intravenous line placement. She takes Tums. VS: P = 87, BP = 110/70 mmHg, R = 12, T = 36.6 °C)

Answer 6

Since the patient’s shortness of breath and/or positional presyncope may be cardiac in origin, I would –

order an echocardiogram if the CT scan demonstrated a pericardial effusion or possible compression of cardiovascular structures.

Moreover, I would have the echocardiogram performed in the upright and supine positions to determine the effects of the mass and positioning on cardiac function.

Also, an echocardiogram may be helpful in identifying any cardiac defects or dysfunction associated with her Down syndrome or myasthenia gravis.

Myasthenia gravis can have direct cardiac effects leading to mild hypertension, first degree AV block, A-fib, myocarditis, and diastolic dysfunction, while 50% of Down syndrome patients have associated cardiac defects, such as endocardial cushion defects (refers to a range of defects involving the atrial septum, ventricular septum, and one or both of the AV valves), ventral septal defects, atrial septal defects, persistent patent ductus arteriosus, and tetralogy of Fallot.

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Xtra Q: Would you do an echocardiogram on any Down’s syndrome pt? (see above)

Question 7

Would you order Flow Volume Loops?

(A 36-year-old female presents for biopsy of an anterior mediastinal mass. Her medical history is significant for Down’s syndrome, moderate to severe asthma, and severe gastroesophageal reflux. Her mother states that her daughter is a smoker, gets short of breath at times, and sometimes has difficulty swallowing. The patient is a poor historian and was minimally cooperative during intravenous line placement. She takes Tums. VS: P = 87, BP = 110/70 mmHg, R = 12, T = 36.6 °C)

Answer 7

• (Diplomatic Approach Type Question)*
• –*
• Xtra Q – Would you order PFTs?*
• (Sample answer – “I could obtain sufficient information by doing the following….”)*

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While flow volume loops could be beneficial in determining the effects of positioning on the airway and whether the obstruction is fixed or variable and intrathoracic or extrathoracic,

I would NOT order them for this patient because – the evidence suggests that they are poor predictors of the perioperative respiratory complications, provide little information that cannot be obtained from CT, and do not alter the anesthetic plan.

Therefore, rather than order flow volume loops, I would – review a recent CT scan and perform a careful history and physical, observing the patient in both the sitting and supine positions to determine the location of the tumor and the effects of positioning on mass compression of the trachea.

Clinical Notes:

• An increased mid-expiratory plateau noted when the patient’s position is changed from upright to supine is pathognomonic for a variable intrathoracic airway obstruction and an indicator of someone who is at increased risk for airway collapse during the induction of anesthesia.
• The flow-volume loop plots the inspiratory and expiratory airflow (Y-axis) against the flow volume (X-axis) during the performance of maximally forced inspiratory (total lung capacity) and expiratory (residual volume) maneuvers.
• See Figure attached.