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Mediastinoscopy
Mediastinoscopy WILLIAM T. MERRITT, M.D., M.B.A. MARCELO QUEZADO, M.D.
Lymph drains from the hilar area to the subcarinal, paratracheal, and supraclavicular nodal regions. Because of this drainage pattern, a number of pathological conditions can be reached with the mediastinoscope—lymphoma and malignant lung tumors of the lung can be identified, as well as vascular tissue, connective tissue, and bone tumors. Secondary tumors of the mediastinum or lung may be found. Benign tumors, including thymic, thyroid, and tracheal, may be diagnosed. Other uncommon pathology includes thymoma, lipoma, myxoma, and pheochromocytoma. Even hiatal hernia and thoracic aneurysms may be present in the mediastinum. With experience, the only firm contraindication is a permanent tracheostomy, post-laryngectomy. Issues of considerable concern include ascending aortic aneurysms, goiter, innominate artery aneurysm, inoperative tumors, tracheostomy, anterior mediastinal masses, recurrent laryngeal nerve injury, previous mediastinoscopy, superior vena cava (SVC) syndrome, and thoracic inlet tumors (e.g., Pancoast-like mass; and substernal thyroid). Of the several potential approaches for mediastinoscopy, a midline suprasternal entry allows for bilateral assessment of nodal tissue.1–4 A. Preoperative assessment for mediastinoscopy, or any procedure in a patient with known or suspected mediastinal involvement, must be attentive to evidence of tracheobronchial compression (e.g., wheezing, dyspnea, or orthopnea), esophageal involvement (e.g., dysphagia), and changes related to exercise or position. Before anesthesia and surgery, radiation therapy may be useful for large radiosensitive masses. Chest x-rays (CXRs), CT/magnetic resonance imaging (MRI) examinations of chest and neck, echocardiography (echo), pulmonary function tests (PFTs), and flow-volume loops (supine and upright) help define the relative functional location and dynamic nature of the obstructing mass and the extent of the airway or vascular compromise. Mediastinal masses may lead to the SVC syndrome with an increased risk of major venous bleeding. B. Place pulse oximeter and arterial catheter on the side of the mediastinoscopy and an indirect BP monitor on the contralateral arm to evaluate for innominate or subclavian artery compression by the mediastinoscope. Insert a large-bore IV line before biopsies are taken and check that blood is immediately available. Patients who are debilitated may benefit from a mediastinoscopy under local anesthesia. However, general anesthesia is preferred by most. Evidence of airway compromise requires special consideration. Those with intrathoracic tracheobronchial obstruction may benefit from intubation while spontaneously breathing. Every effort should be made to determine if the cell type is 308
known to be radiotherapy or chemotherapy sensitive; such treatment may shrink the tumor and decrease or ablate the obstructive symptoms. Muscle paralysis, which improves surgical conditions and lessens the likelihood of sudden movement, may lead to airway collapse and inability to ventilate the patient. Availability and institution of cardiopulmonary bypass (CPB) is potentially lifesaving in such settings. Those with extrathoracic obstruction may benefit from awake intubation, assessment of the obstruction, and placement of a small diameter endotracheal tube through the narrowed area, under direct vision. Parasternal mediastinotomy (Chamberlain procedure) allows diagnosis and staging of left upper lobe lesions and the presence of mediastinal invasion. A small incision is made at the left second or third intercostal cartilage. This procedure can be done with local anesthesia, sedation, or general anesthesia with laryngeal mask airway (LMA) or endotracheal tube (ETT). Invasive monitoring should not be needed. Complications include rare bleeding, which might require a more extensive thoracotomy or sternotomy, with appropriate anesthesia interventions. C. While mediastinoscopy by experienced surgeons and anesthesiologists is a safe procedure, with reported mortality of less than 0.1% and morbidity of about 1.5%, reported risks include hemorrhage, pneumothorax, hemo-mediastinum with cardiovascular collapse, mechanical pressure on the innominate (brachiocephalic) artery, hemiparesis, phrenic or recurrent laryngeal nerve injury, esophageal injury, tumor spread, air embolism, chylothorax, infection, and tracheal collapse after the procedure. If the mediastinoscopy is to immediately precede thoracotomy, drug selection should anticipate a shortened procedure necessitated by the findings of the mediastinoscopy. For urgent conversion to an open thoracotomy, sternotomy or lateral thoracotomy are possibilities, depending on patient stability. Lung separation will be beneficial (double-lumen endotracheal tube [DLT], or bronchial blocker). REFERENCES 1. Ponn RB: Mediastinoscopy and mediastinotomy. In: Yang SC, Cameron DE, editors: Current therapy in thoracic and cardiovascular surgery, St. Louis, 2004. Mosby. 2. Dosios T, Theakos N, Chatziantoniou C: Cervical mediastinoscopy and anterior mediastinotomy in superior vena cava obstruction, Chest 128 (3):1551–1556, 2005. 3. Ehrenwerth J, Brull SJ: Anesthesia for thoracic diagnostic procedures, In: Kaplan JA, Slinger PD, editors: Thoracic anesthesia, ed 3, Philadelphia, 2003, Churchill Livingstone. 4. Datta D, Lahiri B: Preoperative evaluation of patients undergoing lung resection surgery, Chest 123:2096–2103, 2003.
309
MEDIASTINOSCOPY Patient for MEDIASTINOSCOPY A
Clinical evaluation Cardiovascular pulmonary status Cerebrovascular circulation (TIAs?) Myasthenic syndrome Airway patency
Chest firm, CT scan of chest, flow-volume loops Hematocrit Blood typed and cross-matched
Evaluate for SVC obstruction
SVC obstruction
No SVC obstruction
Start IV in lower extremity
Start IV in upper extremity
B
Preparation and monitoring
C Choose anesthetic technique
IV sedation with local anesthetic infiltration
On operative side: • Radial arterial line • Pulse oximeter On contralateral side: • BP cuff Large–bore IV(s)
General anesthesia
Normal airway and asleep intubation
Tracheal compression
Awake intubation
Armored ETT Controlled ventilation
Potential intraoperative complications Hemorrhage (tear, biopsy) Pneumothorax Pneumomediastinum Pneumopericardium Venous air embolism Tracheal compression or injury Compression of innominate artery Esophageal injury Thoracic duct injury Hypercarbia, hypoxia Bradycardia, dysrhythmias, cardiac arrest Left recurrent laryngeal nerve damage Phrenic nerve damage
Emergency thoracotomy
Cerebrovascular insufficiency (hemiparesis) Flattened arterial tracing (simulated cardiac arrest)
Lymph drains from the hilar area to the subcarinal, paratracheal, and supraclavicular nodal regions. Because of this drainage pattern, a number of pathological conditions can be reached with the mediastinoscope—lymphoma and malignant lung tumors of the lung can be identified, as well as vascular tissue, connective tissue, and bone tumors. Secondary tumors of the mediastinum or lung may be found. Benign tumors, including thymic, thyroid, and tracheal, may be diagnosed. Other uncommon pathology includes thymoma, lipoma, myxoma, and pheochromocytoma. Even hiatal hernia and thoracic aneurysms may be present in the mediastinum. With experience, the only firm contraindication is a permanent tracheostomy, post-laryngectomy. Issues of considerable concern include ascending aortic aneurysms, goiter, innominate artery aneurysm, inoperative tumors, tracheostomy, anterior mediastinal masses, recurrent laryngeal nerve injury, previous mediastinoscopy, superior vena cava (SVC) syndrome, and thoracic inlet tumors (e.g., Pancoast-like mass; and substernal thyroid). Of the several potential approaches for mediastinoscopy, a midline suprasternal entry allows for bilateral assessment of nodal tissue.1–4 A. Preoperative assessment for mediastinoscopy, or any procedure in a patient with known or suspected mediastinal involvement, must be attentive to evidence of tracheobronchial compression (e.g., wheezing, dyspnea, or orthopnea), esophageal involvement (e.g., dysphagia), and changes related to exercise or position. Before anesthesia and surgery, radiation therapy may be useful for large radiosensitive masses. Chest x-rays (CXRs), CT/magnetic resonance imaging (MRI) examinations of chest and neck, echocardiography (echo), pulmonary function tests (PFTs), and flow-volume loops (supine and upright) help define the relative functional location and dynamic nature of the obstructing mass and the extent of the airway or vascular compromise. Mediastinal masses may lead to the SVC syndrome with an increased risk of major venous bleeding. B. Place pulse oximeter and arterial catheter on the side of the mediastinoscopy and an indirect BP monitor on the contralateral arm to evaluate for innominate or subclavian artery compression by the mediastinoscope. Insert a large-bore IV line before biopsies are taken and check that blood is immediately available. Patients who are debilitated may benefit from a mediastinoscopy under local anesthesia. However, general anesthesia is preferred by most. Evidence of airway compromise requires special consideration. Those with intrathoracic tracheobronchial obstruction may benefit from intubation while spontaneously breathing. Every effort should be made to determine if the cell type is 308
known to be radiotherapy or chemotherapy sensitive; such treatment may shrink the tumor and decrease or ablate the obstructive symptoms. Muscle paralysis, which improves surgical conditions and lessens the likelihood of sudden movement, may lead to airway collapse and inability to ventilate the patient. Availability and institution of cardiopulmonary bypass (CPB) is potentially lifesaving in such settings. Those with extrathoracic obstruction may benefit from awake intubation, assessment of the obstruction, and placement of a small diameter endotracheal tube through the narrowed area, under direct vision. Parasternal mediastinotomy (Chamberlain procedure) allows diagnosis and staging of left upper lobe lesions and the presence of mediastinal invasion. A small incision is made at the left second or third intercostal cartilage. This procedure can be done with local anesthesia, sedation, or general anesthesia with laryngeal mask airway (LMA) or endotracheal tube (ETT). Invasive monitoring should not be needed. Complications include rare bleeding, which might require a more extensive thoracotomy or sternotomy, with appropriate anesthesia interventions. C. While mediastinoscopy by experienced surgeons and anesthesiologists is a safe procedure, with reported mortality of less than 0.1% and morbidity of about 1.5%, reported risks include hemorrhage, pneumothorax, hemo-mediastinum with cardiovascular collapse, mechanical pressure on the innominate (brachiocephalic) artery, hemiparesis, phrenic or recurrent laryngeal nerve injury, esophageal injury, tumor spread, air embolism, chylothorax, infection, and tracheal collapse after the procedure. If the mediastinoscopy is to immediately precede thoracotomy, drug selection should anticipate a shortened procedure necessitated by the findings of the mediastinoscopy. For urgent conversion to an open thoracotomy, sternotomy or lateral thoracotomy are possibilities, depending on patient stability. Lung separation will be beneficial (double-lumen endotracheal tube [DLT], or bronchial blocker). REFERENCES 1. Ponn RB: Mediastinoscopy and mediastinotomy. In: Yang SC, Cameron DE, editors: Current therapy in thoracic and cardiovascular surgery, St. Louis, 2004. Mosby. 2. Dosios T, Theakos N, Chatziantoniou C: Cervical mediastinoscopy and anterior mediastinotomy in superior vena cava obstruction, Chest 128 (3):1551–1556, 2005. 3. Ehrenwerth J, Brull SJ: Anesthesia for thoracic diagnostic procedures, In: Kaplan JA, Slinger PD, editors: Thoracic anesthesia, ed 3, Philadelphia, 2003, Churchill Livingstone. 4. Datta D, Lahiri B: Preoperative evaluation of patients undergoing lung resection surgery, Chest 123:2096–2103, 2003.
309
MEDIASTINOSCOPY Patient for MEDIASTINOSCOPY A
Clinical evaluation Cardiovascular pulmonary status Cerebrovascular circulation (TIAs?) Myasthenic syndrome Airway patency
Chest firm, CT scan of chest, flow-volume loops Hematocrit Blood typed and cross-matched
Evaluate for SVC obstruction
SVC obstruction
No SVC obstruction
Start IV in lower extremity
Start IV in upper extremity
B
Preparation and monitoring
C Choose anesthetic technique
IV sedation with local anesthetic infiltration
On operative side: • Radial arterial line • Pulse oximeter On contralateral side: • BP cuff Large–bore IV(s)
General anesthesia
Normal airway and asleep intubation
Tracheal compression
Awake intubation
Armored ETT Controlled ventilation
Potential intraoperative complications Hemorrhage (tear, biopsy) Pneumothorax Pneumomediastinum Pneumopericardium Venous air embolism Tracheal compression or injury Compression of innominate artery Esophageal injury Thoracic duct injury Hypercarbia, hypoxia Bradycardia, dysrhythmias, cardiac arrest Left recurrent laryngeal nerve damage Phrenic nerve damage
Emergency thoracotomy
Cerebrovascular insufficiency (hemiparesis) Flattened arterial tracing (simulated cardiac arrest)