Mediastinoscopy is a surgical procedure that is performed in the operating room. It requires a cardiothoracic or general surgeon trained in mediastinoscopy capable of performing an emergency thoracotomy and/or sternotomy. The procedure also requires general anesthesia and thus requires an anesthesiologist and operating room support staff.

Mediastinoscopy can be performed under local or general anesthesia. General anesthesia is the technique of choice at most institutions if the patient has no preoperative signs or symptoms of airway obstruction.[7][2] 

A preoperative evaluation of a patient undergoing a mediastinoscopy is important in decreasing morbidity and mortality. Particular attention should be paid to respiratory symptoms such as wheezing, dyspnea, and orthopnea. It is important to find out whether the respiratory symptoms are exacerbated by exercise or by assuming the supine position which may indicate airway obstruction secondary to a mediastinal mass. Preoperative workup should include chest x-ray with posteroanterior and lateral views, CT scan of the chest and neck pulmonary function tests with flow-volume loops. If tracheal deviation is suspected, specific studies such as neck films or tomograms should be obtained to evaluate the location and extension of the mass as well as the degree of airway compromise. Flow-volume loops in both the upright and supine positions are useful in determining whether the obstruction is fixed, and whether it is intrathoracic or extrathoracic. 

An intravenous line must be in place before proceeding to the operating room. The general anesthetic technique can involve inhalational or intravenous agents, or most commonly, a combination of the two. Following induction and intubation, the use of muscle relaxants provides the surgeon with an operative field safe from sudden movements, which might lead to injury of the adjacent organs by the mediastinoscope.  If the preoperative workup is indicative of airway compromise, the patient may be intubated via an awake fiberoptic technique where the patient remains spontaneously breathing. The patient is intubated with a standard single lumen endotracheal tube unless there are contraindications that require one-lung ventilation. In that case, the patient may be intubated with a large 7.5 mm or above a single lumen tube to allow the easy passage of a bronchial blocker or a double lumen endotracheal tube. Following intubation, additional vascular access is established in the form of another large bore IV and an arterial catheter. The arterial catheter allows for beat-to-beat blood pressure monitoring which may be able to detect vascular compression or massive hemorrhage during the procedure and also allows for arterial blood gases to be regularly checked during the procedure. To detect innominate artery compression by the mediastinoscope when inserted, constant palpation of the right radial or carotid pulse, placement of a right radial arterial line, or monitoring of a continuous plethysmographic tracing of a pulse oximeter is advocated.[10]

Mediastinoscopy is performed in the operating room under general anesthesia. A patient is generally in the supine position for the procedure unless an anterior mediastinal mass causes airway compromise when lying flat. In a patient without such a mass, intravenous induction is performed, and following intubation, the patient’s head is extended and turned to the side. A 3-cm incision is performed 2 cm above the suprasternal notch between the anterior borders of the sternocleidomastoid muscle. The superficial fascia of the neck, deep cervical fascia, and pretracheal fascia must be dissected to reach the level of the trachea. Blunt dissection down to the anterior trachea allows entrance into the superior mediastinum. As the tract continues to be developed via blunt dissection, a tract into the superior mediastinum will develop between the anterior trachea and posterior to the great vessels. A mediastinoscope is then inserted and advanced along the tract allowing for the sampling of lymph nodes and masses.[2]

During the procedure when the mediastinoscope is inserted, it can cause compression of the innominate artery. This can lead to a decrease in pulse oximeter signal and blood pressure when these are placed in the right upper extremity, as a result of the decreased blood flow to the extremity when the artery is compressed. Compression of the innominate artery can lead to intracerebral hypoperfusion which can in turn lead to cerebral ischemia and stroke.

Mediastinoscopy is not a benign procedure; the morbidity associated with the procedure is reported to be between 1.5% to 3%, with an overall mortality rate of 0.09%. Intraoperative complications can occur with mediastinoscopy and include bleeding, which is the most common complication of this procedure. Injury to the great vessels causes hemorrhage that can be life-threatening; an emergent thoracotomy or median sternotomy may be necessary to gain control of the hemorrhage while using the mediastinoscope to tamponade the site of bleeding. The procedure has a risk of air embolism given that the patient is in a head-up position/reverse Trendelenburg and the mediastinoscope can lead to vascular injury which could lead to air being entrained into the vascular system; this can be monitored via end-tidal CO2 and end-tidal nitrogen. Some recommend the use of precordial Doppler to monitor for any venous air embolism. Instrumentation can lead to airway rupture; however; this complication requires an immediate thoracotomy. During the procedure, the recurrent laryngeal nerve can be injured. The left is at more risk because of its more caudal path under the aorta. Bilateral recurrent laryngeal nerve injury can lead to complete respiratory failure and the need to re-intubate and then perform a surgical airway on the patient. Damage to the thoracic duct can lead to chylothorax.

There are times when mediastinoscopy is indicated in the presence of an anterior mediastinal mass. It is important that surgeon, anesthesiologist, and operating room staff appreciate potential complications of the mass. The patient may not be able to lie flat, making endotracheal intubation more difficult. Even in the presence of successful intubation with proper airway placement, the airway may be compromised by the mass distal to the airway after muscle paralysis is induced. Therefore, it is recommended that muscle relaxants be avoided in high-risk patients and that the patient be intubated while spontaneously breathing either via a fiberoptic bronchoscope or direct/indirect laryngoscopy following mask induction. An otorhinolaryngology (ENT) surgeon competent with rigid bronchoscopy should be present if necessary to bypass the obstruction. Changing patient position from to supine or either lateral or prone may be a temporizing measure that relieves the obstruction of the mass on the airway. In cases where there is a large anterior mediastinal mass that may result in cardiovascular collapse with induction of anesthesia, cardiopulmonary bypass should be available.

Patients who have suspected airway obstruction due to a mediastinal mass on physical examination should undergo pulmonary function tests (PFTs) with flow-volume loops. The tests should be performed in both the upright and supine positions. If the PFTs show obstruction while supine during inhalation, the patient’s mass is extra-thoracic, if the obstruction occurs during expiration, the patient’s mass is intrathoracic. A review of CT imaging can be extremely helpful in evaluating any compression or deviation of the great vessels.

In patients with a large mediastinal mass, SVC syndrome may be present. Obstruction of the superior vena cava will cause facial swelling, distension of neck, development of collateral venous drainage along the thoracic wall. It associated with dyspnea and dysphagia commonly. Diagnostically, it can be seen on imaging. A positive Pemberton’s sign also characterizes it. A positive Pemberton’s sign occurs when a patient lifts both of their arms over their head in the upright position causing marked facial plethora to occur, indication profound compression of the jugular veins. It is important to have intravenous access in these patients in the lower extremities because of the resistance of upper extremity drainage being recirculated.[11][2][12][13]

Along with endobronchial ultrasound with biopsy, mediastinoscopy is an important clinical procedure performed in the diagnosis of disease pathologies that occur in the mediastinum, most notably bronchogenic carcinoma. It is recommendations that patients that patients initially receive an endobronchial ultrasound biopsy before induction therapy, and then mediastinoscopy following the therapy. Many centers are using video-assisted mediastinoscopy as it improves surgical visualization and allows the surgeon to use multiple instruments at once. These are both methods for staging non-small cell lung cancer. It is expected that both treatment modalities will increase in number in the future. A single institution study showed that mediastinoscopy was marginally cheaper than the endobronchial ultrasound biopsy.[14][15]

Mediastinoscopy is a well-known and common procedure. It is paramount to educate the patient, physicians, all others that are involved in mediastinoscopy cases what to expect before, during, and following the procedure. In many instances, there is a close association of the procedure with a lung cancer diagnosis, and patient care must be well coordinated with other physicians and care staff to make sure the patient is optimized for the procedure. As ultrasonic methods become more advanced endobronchial ultrasound with biopsy of the mediastinum may largely overtake mediastinoscopy, but at this time both have a major role in thoracic surgery.