2 Objectives Indications . The nature of the procedure. Important anesthetic management principles.Anesthetic technique.Complications.
3 IndicationsMediastinoscopy is commonly performed before thoracotomy to establish the diagnosis or to determine the resectability of lung carcinoma.
4 The nature of the procedure After a suprasternal notch incision
5 A tunnel is created by blunt dissection along the anterior and lateral walls of the trachea into the mediastinum down to the subcarinal area, for direct inspection and biopsy of superior mediastinal lymph nodes.
6 The mediastinoscope passes anterior to the trachea but behind the aortic arch
7 Schematic diagram showing placement of a mediastinoscope into the superior mediastinum Lt recurrent laryngeal nerveRight common carotidLeft common carotidRight subclavianLeft subclavianInnominate arteryAortic archSuperior vena cava
8 Anatomic structures that can be compressed by the mediastinoscope are: 1)Thoracic aorta: (rupture, reflex bradycardia)2) Innominate artery: (decreased right carotid blood flow; can cause cerebrovascular symptoms, and decreased right subclavian blood flow; can cause loss of the right radial pulse).3) Trachea: (stimulus to cough, inability to ventilate)4) Vena cava: (risk of hemorrhage with superior vena cava syndrome)
9 Relative contraindication to mediastinoscopy include: Superior vena cava syndrome Severe tracheal deviation Cerebrovascular disease Thoracic aortic aneurysm
10 Special anesthetic considerations: In addition to the routine preanesthetic evaluation, look for signs and symptoms of:1) OBSTRUCTION OR DISTORTION OF THE UPPER AIRWAY2) OBSTRUCTION OF THE SUPERIOR VENA CAVA3) IMPAIRED CEREBRAL CIRCULATION
11 Anesthetic technique: General anesthesia with muscle relaxation and positive pressure ventilation (facilitates dissection and management of complications, minimizes air embolism)
12 During mediastinoscopy the anesthesiologist attention is primarily focused on management of major complications which are:Hemorrhage and hypovolemiaCompression of the great vesselsPneumothoraxRecurrent laryngeal nerve injury
13 Significant (occasionally) massive hemorrhage: the most frequent major complication it requires immediate thoracotomy
14 The anesthesiologist should: 1) Rapidly begin volume replacement through one or more large-bore intravenous cannulas that have been placed before induction of general anesthesia.2) Send for blood that was reserved for the patient preoperatively.3) Support the circulation pharmacologically until volume replacement is achieved4) Ensure adequate oxygenation and ventilation.5) Administer atropine for reflex bradycardia from aortic compression.6) Reduce or discontinue the dose of all anesthetic drugs until normovolemia is established.7) If hemorrhage originates from tear in the superior vena cava, a peripheral line should be rapidly placed in the lower extremity.
15 Compression of the great vessels: The vessel most commonly compressed is the innominate artery: diminished blood flow to the right subclavian and right carotid arteries.(This phenomenon of special significance in payients with preexisting compromised cerebral circulation)
16 The vessel most commonly compressed is the innominate artery: (management) 1)Require monitoring of the right upper extremity blood pressure; via a right radial arterial line, or alternatively, a pulse oximeter probe on the right hand that signals diminution of the blood flow by changes in the signal strength.2) Any decrease in the right radial artery pressure requires repositioning of the mediastinoscope.
17 B) Mechanical stimulation of the aorta can cause arrhythmias, and compression of the aorta can cause reflex bradycardia.Sudden changes in the pulse or the blood pressure during mediastinoscopy, may empirically be treated by repositioning of the mediastinoscope.Atropine is given for persistent bradycardia.
18 Pneumothorax (usually seen postoperatively) However patients should be monitored for signs of intraoperative pneumothorax:Increased peak airway pressureTracheal shiftDistant breath soundsHypotensionCyanosisThat requires immediate decompression
19 Recurrent laryngeal nerve injury: The vocal cords should be visualized while the patient is spontaneously breathing (at the time of extubation).Postoperative laryngeal obstruction is a problem if the vocal cords are not moving or in the midline.