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Anterior Mediastinal Anterior Mediastinal masses:masses:

An Anesthetic Challenge An Anesthetic Challenge

By M. Goh , x. Liu and Y. GohSingapore general hospital

Anesthesia 1999

Case Report

Anterior mediastinal masses are uncommon but when present

they pose serious challenges for the anesthetist.

introduction

By nature of their anatomical location they produce three problems:

compression of the heartcompression of the large

vesselscompression of the Trachea and

main Bronchi

introduction

Compression of the airway can be insidious when it is intrathoracic and at the bronchial level.The patient can be asymptomatic yet have airway compression which only manifest at the induction of anesthesia when voluntary control of the airway is lost.

introduction

The anesthestist who is unprepared will face a catastrophic situation of total obstruction of the airway leading to death of the patient.

introduction

20 y old woman presented for diagnostic biopsy of anterior mediastinal mass.Had history of cough….1 monthNo history of Dyspnoea ,stridor or noisy breathing.CXR showed massive mediastinal mass.CT confirmed this finding as well as compression of both main bronchi.

Case History

An awake intubation was done with 100 mcg of fentanyl and topical anesthesia of the oropharynx.Size 7 tracheal tube was inserted easily past the cords.Bilateral breath sounds were ascertained and the tube secured.

Case History

Initial manual ventilation showed no increase in peak airway presure.Thiopentone and atracurium were admenistered and anesthesia was maintained with isoflurane and surgery commenced.

Case History

It was noticed that the peak airway pressure had increased to 50 cmH2O.Auscultation revealed coarse inspiratory and expiratory rhonchi.No change in lung sounds after salbutamol administration.

Case History

High airway pressure developed -varied between 42 and 50cmH2O-and ventilation became difficult but Oxygenation remained satisfactory with SpO2 98-100%

Frozen section revealed a lymphoma and surgery was terminated.Reversal was given.

Case History

In the view of the fact that the patient was not fully awake and the airway pressure was still high , it was decided not to extubate her and she was transferred to the intensive care unit for elective ventilation.

Case History

When the patient awoke from the anesthetic and began spontaneous respiration , the airway pressure started to decrease .4 hours after arrival in ICU she was extubated and was able to maintain adequate oxygenation on 2L/m O2.nasal cannula.

Case History

The literature is replete with examples of patients with anterior mediastinal masses and undiagnosed or underestimated airway obstruction who after induction and muscle relaxation became impossible to ventilate and ultimately died.

Discussion

Even asymptomatic patients have developed live threatening complications.

Discussion

The management of such cases should focus on two aspects First, estimate of the presence and degree of airway obstruction.Second, serious consideration should

be given to avoiding general anesthesia.

Discussion

It is crucial to assess the patency of the airway at two levelstracheal and bronchial level.

In the patients history, symptoms of airway obstruction should be sought. In particular dyspnoea or noisy breathing at rest ,on exertion and in different positions.

Assessment of the trachea and bronchi

On examination, stridor, wheezes, rhonchi and diminished breath sounds should be carefully looked for, again with patient in different positions.

Assessment of the trachea and bronchi

PA CXR will allow measurement of the tracheal diameter at the level of the clavicles, although for technical reasons may overestimate the diameter.Lateral View will show the degree of compression in anterioposterior direction.

Investigations:

CT scan will demonstrate airway compression in addition will permit accuarte measurement of the airway diameters.It will also determine the precise level and extent of compression of the tracheobronchial tree.

Investigations:

The degree of tracheal compression on CT can predict anesthetic difficulty with the airway under anesthesia.

Severe tracheobronchial compression is defined as a decrease in luminal area by grater than one third of the normal.

Pulmonary flow volume loop studies should be carried out in the supine and upright positions.

Cont.. Investigations..

Lcal Anesthesia Vs. GA

Many authors have emphasized the dangers of general anesthesia in such patients especially those with symptoms of respiratory obstruction.

Tracheostomy in such cases will prove futile because the obstruction is usually intrathoracic and close to or below the carina.

Cont…Discussion

Reasons for the danger of GA

- Lung Volume is reduced as little as 500-1500 ml under GA

- Relaxation of broncheal smooth muscle lead to grater compressibility of the airway from the overlying mass.

Cont.. discussion

- The loss of spontaneous diaphragmatic movement induced by muscle relaxants reduces the normal transpleural pressure gradient which dilates the airway.

This decreases the caliber of the airway and enhances the effect of extrensic compression.

Cont.. discussion

- General anesthesia should be avoided and biopsy should be obtained

under local anesthesia if possible.

- GA to be used only as the last resort.

- When GA has to be used , spontaneous respiration should be preserved.

Authors SuggestionsAuthors Suggestions

-Team Approach for GA:A team of ENT surgeon, cardiac surgeon,

cardiopulmonary bypass personnel and a second anesthetist should be assembled and the role of each should be defined and agreed upon.

-Equipments should be assembled and ready for immediate use including:fiberoptic bronchoscopes, rigid bronchoscopes, tracheal tubes of various sizes and cardiopulmonary bypass equipment.

Authors SuggestionsAuthors Suggestions

-Large bore peripheral IV cannula preferably in lower extremity along with arterial line and pulmonary catheter.

-Patients with more than 50% obstruction of the airway at the level of the lower trachea and main bronchi have their femoral vessels cannulated in readiness for cardiopulmonary bypass.-Those with less obstruction should have femoral area prepared and draped for cannulation.

Authors SuggestionsAuthors Suggestions

-Awake fiberoptic bronchoscopy to be done under sedation and topical anesthesia.-Degree and level of obstruction should be noted.-The least obstructed bronchus also should be noted.-If ventilation proves difficult and oxygenation is not being maintained , an attempt to pass the tracheal tube down the least obstructed bronchus.

Authors SuggestionsAuthors Suggestions

-If the passage of the ETT is not possible the ENT surgeon should try to pass a rigid scope down the least obstructed bronchus. -Failing This , Cardiopulmonary bypass should be instituted as lifesaving measure. - A surgical decision then has to be made whether or not to debulk the mass through an open sternotomy.

Authors SuggestionsAuthors Suggestions

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