Tibor Krajc and Michael Rolf Mueller
INDICATIONS
Standard Indications
Cervical mediastinoscopy has been originally thought up by an otorhinolaryngologist as a means of excluding patients with unfavorable prognosis from further resectional treatment of lung cancer in times when no computerized tomography existed. Nonselective application created vast numbers of patients undergoing mediastinoscopy and established the procedure as very safe from the statistical point of view, albeit with rarely occurring and notoriously discussed fatal complications.
This classical indication for nodal staging of lung cancer remains to be the most frequent reason for performing mediastinoscopy. Although limited to nodal stations adjacent to trachea and main bronchi in its standard form, diagnostic accuracy superior to imaging studies has long been keeping mediastinoscopy on the throne of gold standard. Hundred percent reliability of staging by mediastinoscopy cannot, by definition, be reached for two obvious reasons: Not all N2 mediastinal nodal stations are accessible by the technique; and tumor-related changes may be located in the nonbiopsied part of the node or in another node of the same station. The first limitation can be overcome by utilizing extended mediastinoscopy (stations 5 and 6), a combination of EUS/EBUS (stations 3p, 8, 9), or VATS (stations 3a, 5, 6, 8, 9). Avoiding the second limitation constitutes the core idea of supermediastinoscopies (TEMLA and VAMLA)—only removing entire nodes and removing all of them can provide complete mediastinal nodal staging.
Endoluminal needle staging techniques had to prove and have proven their usefulness by comparison to mediastinoscopy. High specificity and low negative predictive value make these techniques ideal for detection but insufficient for exclusion of mediastinal disease. Staging algorithms have evolved that utilize the initially concurring endoscopic and surgical techniques as complementary—based on initial imaging studies the invasive staging methods are applied selectively to reach the best possible sensitivity and predictive values (Fig. 4.1).
Figure 4.1 Staging algorithm with selective utility of mediastinoscopy. *Not clearly stated in the guidelines: If suspicion persists after negative EBUS/EUS, mediastinoscopy may be performed; otherwise proceed to surgery. Performing mediastinoscopy in EBUS/EUS negative patients with normal N2 nodes on PET/CT little or no value to staging accuracy. Based on ACCP Guidelines 2013.
Although not clearly supported by prospective trials, surgery after induction treatment is generally accepted as a valid therapeutic option for stage IIIA NSCLC if nodal downstaging can be proven by tissue analysis. Remediastinoscopy, although not widely performed, remains a reliable restaging tool in these patients.
Mediastinal lymphadenopathy unrelated to lung cancer is mostly successfully evaluated by endoluminal needle techniques but occasionally may require mediastinoscopy, which offers highly reliable results for tissue diagnosis of granulomatous diseases, lymphomas, or metastatic spread of extrathoracic malignancies. Tumors accessible to mediastinoscopy may require analysis of larger tissue samples not obtainable by core-needle biopsy.
Contraindications
All contraindications of mediastinoscopy are relative.
The inability to extend the neck for whatever reason may be problematic not only for insertion of the scope but also for manipulation via its channel due to patient’s chin obstructing the route. This can mostly be overcome by rotation of the head to one side.
Previous sternotomy is not a contraindication per se but may become a problem in case of hemorrhagic complications, as the left innominate vein, superior vena cava (SVC), the ascending aorta or pericardium may adhere to the posterior aspect of sternum and suffer damage during emergency resternotomy. Previous aortic arch surgery or aneurysm might represent a relative contraindication as well.
Previous tracheostomy, definitive, persisting, or healed, while isolated from the neck incision, does not represent an absolute contraindication.
Large retrosternal goiter may be removed via transcervical access and mediastinoscopy for exploration of peritracheal pathology may be done in the same session.
All previous interventions in mediastinum, but especially in peritracheal regions, can lead to scarring and difficult dissection (previous mediastinoscopy, tracheal resection, drainage or vacuum-assisted closure for anterior mediastinitis, previous lung resection with en bloc mediastinal lymphadenectomy especially on the right) with the occasional need to abandon mediastinoscopy. Previous esophagectomy with retrosternally placed conduit can hinder the access to anterior tracheal wall.
SVC syndrome is not a contraindication for mediastinoscopy if appropriate precautions are taken.
PREOPERATIVE PLANNING
Clinical examination relevant to mediastinoscopy consists of verification of sufficient neck extension, neck palpation to exclude peripheral lymphadenopathy, presence of goiter, and high-riding innominate artery pulsating in the jugular notch. Tracheal deviation may also be detected by palpation. Subclinical SVC syndrome can yield a positive Pemberton test.
The surgeon should be acquainted in detail with the mediastinal anatomy of the patient and eventual variations and anomalies. Contrast-enhanced CT provides not only data on size and location of lymph nodes or tumors, but also sufficient information on great vessels, that is, high-riding innominate artery, Bovine arch anatomy (left common carotid coming off innominate artery), lobus venae azygos and varicose dilation of the azygos vein in patients with portal hypertension, aneurysm or atheromatous changes of aortic arch and its arteries, and presence of SVC compression or thrombosis. Three-dimensional reconstruction may even identify aberrant bronchial arteries. CT enables better planning of the procedure in the rare case of situs inversus viscerum. Tracheal deviation and compression and esophageal dilation are also relevant for the mediastinoscopist. Presence and extent of retrosternal goiter and its potential conflict with access to peritracheal areas can be evaluated.
Cross-matching blood units preoperatively can save time in case of catastrophic bleeding. Major vascular access and arterial blood pressure monitoring are recommended for patients evaluated as ASA3 or worse and those who could undergo lung resection during the same session if frozen sections are reliably negative. Sternotomy and thoracotomy set must be ready in the room or on the side table. An assistant should be present in the theater or rapidly available for eventual emergencies.
SURGERY
Positioning
One arm is abducted and provided with intravenous access, preferably on the side contralateral to tumor. Upon intubation the patient is left in supine position with a gel cushion or a soft roll placed directly under the shoulder blades (i.e., level Th5) to extend the neck and a stabilizing cushion supporting the occipital region to prevent spontaneous rotation. The patient is positioned with the head as near the “cranial” edge of the table to keep the working conditions ergonomic. Orotracheal tube is kept in the corner of the mouth on the side of the abducted arm.
The table is moved into slight anti-Trendelenburg position until proximal part of sternum lies horizontally to improve the working angle of the mediastinoscope and instruments inserted.
The operating field is prepared and draped at the level of cricoid cartilage proximally, xiphoid process distally, and midclavicular lines laterally. This allows for a rapid midline sternotomy when bleeding from large systemic arteries occurs. Other vascular injuries requiring additional or stand-alone thoracotomy can be temporarily controlled by gauze packing until the patient is repositioned.
Figure 4.2 depicts one of the possible arrangements of the patient and the operating team.
Rigidity of cervical spine causing the chin get in the way of mediastinoscope can be overcome by gentle rotation or reclination. Some surgeons prefer to sit mainly to get a comfortable view directly through the scope. Video-mediastinoscopy can be done completely without looking through the instrument and therefore the ergonomics are better while standing.
Figure 4.2 Operating room setup for videomediastinoscopy.
Right-handed surgeons hold and move the scope around with their left hand while dissecting in mediastinum. A plastic bag for the suction devices (suctioning electrode, large-bore suction tube) is placed on the side of the dominant hand. Mediastinoscope positioning arm is attached to the table on the nondominant side of the surgeon.
Instruments
The classical Carlens mediastinoscope is 6 cm shorter than modern mediastinoscopes and slightly (1.2 mm) narrower in diameter. Some surgeons prefer this scope for better maneuverability especially in fibrotic mediastinum and in patients with a short or rigid neck.
Modern videomediastinoscopes (Dahan–Linder by Wolf, Huertgen by Storz) have variably long blades (16 cm, 19 cm) that can be distracted parallelly or divergently to create space for bimanual manipulation with increased mobility of instruments.
Dahan–Linder mediastinoscope by Wolf (Richard Wolf GmbH, Knittlingen, Germany) can be fully dismantled, and its dorsal blade has an atraumatic lip protruding dorsally and beyond the distal end. Light cable is attached separately on the right side of the scope, and camera head to the universal camera connector at the top of the handle.
Linder–Huertgen videomediastinoscope by Storz (KARL STORZ GmbH & Co.KG, Tuttlingen, Germany) has both the camera and the light connector integrated in the compact handle and its dorsal blade is straight at the distal end with no protrusions.
Choosing the make and manufacturer of the scope is a matter of personal preference.
Video- Versus Conventional Mediastinoscopy
Videomediastinoscopy has undoubtedly many advantages over conventional mediastinoscopy. The field of vision is extended and magnified 17 times, which combined with high-definition resolution brings far more detail to the eye of the surgeon. Thus, the dissection, hemostasis, and lymph node biopsy can be more detailed, accurate, and extensive.
Ergonomics are improved when sitting to look directly through the scope, however the surgeons arms have to be elevated and his neck stretched which may lead to overstraining and discomfort during longer procedures. Standing during video-mediastinoscopy keeps the susceptible axial skeleton in a more physiologic position even during bimanual operation.
Videomediastinoscopy provides a better access to and better biopsies of the posterior segment of subcarinal nodes. Also LNR paralysis is less frequent with videomediastinoscopy.
Conventional mediastinoscopy might be beneficial in tight mediastinum as the scope is slightly narrower and shorter, which allows for better mobility. For a surgeon uncomfortable with mediastinal anatomy the 3D view through the scope may improve performance.
Best evidence literature search found higher lymph node yield, better sensitivity, and better negative predictive value with videomediastinoscopy.
Technique
Mediastinoscopy starts with a 3- to 4-cm transverse incision 1 fingerbreadth cranial to jugular notch. Placing the incision too low may cause a spatial conflict of the scope with the manubrium and its limited mobility.
As the circumference of the scope averages centimeter at its widest part, it is advisable to make the incision somewhat longer so as to avoid pressure necrosis or burning of the skin. Covering the operation field with adhesive foil will also prevent inadvertent electric burns and allow for safe digital exploration and dissection in the mediastinum without increasing the risk of contamination.
After dividing the platysma muscle (rarely defined near midline) the deep cervical fascia investing the strap muscles is divided in midline and the strap muscles are retracted laterally. Anterior jugular veins and lower thyroid vessels may be retracted laterally as well or transected. A high-riding innominate artery or the left innominate vein may be encountered and their injury should be avoided. Anterior surface of the trachea covered with pretracheal fascia becomes visible caudal to the thyroid isthmus. Here the highest mediastinal nodes are occasionally encountered and may be easily removed along with fatty tissue.
Upon lifting it gently with forceps the pretracheal fascia is incised with scissors and bluntly separated from the trachea so that the index or middle finger can be inserted into this virtual space. Blunt digital dissection along the anterior surface of the trachea follows. The cartilaginous tracheal rings are felt on the dorsal aspect of the finger while the pulsatile innominate artery crossing ventrally, and the medial aspect of the aortic arch are palpated with the palmar aspect.
The pretracheal (aka perivisceral) fascia in mediastinum encompasses the trachea and esophagus all the way to tracheal bifurcation where it becomes continuous with the fibrous pericardium anteriorly but also extends along the bronchi and surrounds bronchial arteries, lymphatic vessels, and subcarinal lymph nodes. It continues below the bifurcation as the investing fascia of the esophagus. The peritracheal nodes lie outside this fascia, therefore, upon safely entering the mediastinum by keeping the innominate artery outside the finger dissection field, the perivisceral fascia has to be bluntly or sharply penetrated and widely open caudal to innominate artery all the way to bifurcation (Fig. 4.3). To reach the subcarinal nodes, the perivisceral fascia has to be penetrated again under vision at the level of bifurcation, as these nodes lie within the space defined by the fascia.
Digitally opening the perivisceral fascia enables the surgeon to assess the location, size, and consistence of nodes present. Slight lateral mobilization at the level of innominate artery improves the mobility of the scope and decreases the risk of severe compression or laceration of the vessel. Any resistance encountered might be caused by entering the wrong plane or by pressing against great vessels or lymph nodes.
Figure 4.3 Pretracheal (perivisceral) fascia—anatomy and penetration of the fascia in the initial phase of mediastinoscopy.
The mediastinoscope is inserted while gently pulling the innominate artery ventrally with a retractor until the tip of the scope passes underneath. Dissection is performed by a blunt-tip suction monopolar or bipolar electrode by pushing the loose connective and fatty tissue away from trachea and occasionally coagulating the magnified and well-visible small vessels.
Visualizing the trachea and both main bronchi by dissecting under visual control and advancing the scope further along the trachea is essential for ascertaining the anatomical relationships and the actual position of the scope. The movement of the scope should neither follow a straight line nor should the scope be advanced in a drilling fashion the line is rather curved with a dorsal convexity so that the distal elevation of the dorsal spatula acts as a retractor pushing the fatty tissue or pulmonary artery ventrally and allowing further insertion of the scope (Fig. 4.4). Trachea serves as the essential landmark and in case of anatomical disorientation one should always retreat from terra incognita to identify the windpipe.
Cranial aspects of at least one or both main bronchi are usually easily visualized, thus yielding information about the approximate location of azygos vein and right pulmonary artery. Turning the distal end of the scope laterally enables dissection in paratracheal regions. On the right, the azygos vein arching over the right main bronchus enters the superior cava vein on its dorsal aspect. Sometimes transparent mediastinal pleura and the inflated lung parenchyma can be seen retrocavally in thin patients.
The left main pulmonary artery continues along the anterior, superior, and later the dorsal aspect of the left main bronchus. The position of the aortic arch prevents the scope from following the artery further. The distal course of the left recurrent laryngeal nerve curving laterally and anteriorly along the circumference of the aortic arch is identifiable. Ventrally from the tracheal bifurcation the relatively long intra- and extrapericardial course of the right main pulmonary artery can be observed and followed distally to the origin of anterior trunk (Boyden) and even further on its dorsal aspect between the main RPA and right main and intermediate bronchus. The right main pulmonary artery is usually retracted by the scope toward sternum when dissecting in the subcarinal area after the perivisceral fascia has been penetrated.
After advancing the 19-cm scope further caudally beyond the subcarinal nodes the esophagus may be visualized depending on its position subcarinally in the midline or left to it (dorsal to the left main bronchus). However, esophagus may also be vulnerable to inadvertent biopsy dorsally paratracheally on both sides.
Figure 4.4 Superior view of mediastinal anatomy (A) and position of the mediastinoscope during dissection of the subcarinal zone, with right main pulmonary artery retracted by the superior blade (B). Note the “innominate triangle” for entry into aortopulmonary window.
Ectopically originating bronchial arteries may be found crossing or following the distal 1/2 of trachea or crossing over the left main bronchus with branches entering or passing in-between subcarinal nodes.
The border between upper and lower paratracheal nodes is defined by a virtual plane passing transversally at the level of the top of aortic arch on the left and at the intersection of lower border of left innominate vein and trachea on the right. The distinction between the stations 2 and 4 on the right is not based on any natural barrier or configuration—the lymphatic chains in this region are continuous. On the left, the craniocaudal and posteroanterior course of the left laryngeal nerve can help define the border, as the 4L nodes will be usually located dorsally and 2L ventrally from the left recurrent laryngeal nerve.
Sometimes better retraction and visualization in the 2R zone are provided by turning the scope in its long axis 90 degrees clockwise, so that trachea is being pushed contralaterally. On the left side a similar maneuver can improve visualization provided the left recurrent nerve stays in sight. Great care should be taken to avoid direct contact of the edges of dilated spatulae with the nerve.
Unless retreating with the scope, it should be repositioned with parallel and closed arms, or else tissue might get pinched in-between and torn, causing unnecessary bleeding or unwanted jerks of the scope and vascular injury at its tip.
Depending on the indication, either radiologically suspect nodes should be biopsied (diagnostic mediastinoscopy), or all standardly reachable stations should be explored, that is, ideally 2R, 4R, 2L, 4L, and 7 including the posterior segment or at least 4R, 4L, and 7 (staging mediastinoscopy).
Dissecting the Nodes
Surface of the nodes can be exposed by pushing or dissecting the surrounding fatty tissue aside. As everywhere in endoscopic surgery, dissection is greatly facilitated by applying adequate traction and countertraction. Flexibly moving and positioning the tip of the scope (zooming in and out) can provide sufficient traction and countertraction to dissect the node with suction-coagulation device. Alternatively, adding a grasper and having the dilated scope fixed by an assistant or a fixation arm allows for bimanual dissection.
Revealing a sufficient area of the surface of the node minimizes the risk of biopsying a large vessel. A diagnostic puncture with a long fine needle or a dedicated aspiration cannula can also help distinguishing nodes from vessels. Biopsied nodes might bleed from the cut surface or a disrupted nutritive artery, the tissue may be squashed by the biopsy forceps or may come from an unaffected part of the node, and tumor cells from positive nodes may contaminate the mediastinoscopy tract and eventually cause implantation metastasis. Therefore if possible, the best and safest biopsies are obtained by removing an entire node without disrupting its capsule and after eventually clipping its vascularized attachments.
In case a hard or calcified tumor or node is encountered, not allowing biopsy with the sharp but subtle biopsy forceps, direct excision with scalpel no. 11 on a long handle may be necessary. However, the relative position and course of great vessels and airway must be clearly evident.
At the end of mediastinoscopy, most surgeons do not drain the artificially created space in mediastinum.
After the final hemostasis check, the scope is removed and the wound is closed. Some authors advise no suture of the strap muscles to ease the access to pretracheal space in case of future re-exploration. However, a high-riding innominate artery should be covered by the muscle layer.
POSTOPERATIVE MANAGEMENT
Outpatient Mediastinoscopy
Mediastinoscopy can be done safely as an outpatient procedure. Ninety-six percent of all mediastinoscopies including extended ones and in patients with SVC syndrome were performed on an outpatient basis in the largest published series.
The benefits of this approach comprise cost effectiveness, better utilization of hospital beds, avoidance of prolonged waiting periods, and reduced risk of nosocomial infections.
Single-session Versus Two-stage Approach
Several studies have analyzed the effectiveness of frozen section analysis of biopsied nodes and its utility for immediate resection in the same session. The advantages of single-session approach are psychological (patient visits the theater only once), organizational (shorter cumulative operative time), and economical. One percent to 3.6% false-negative results and 94% to 99% sensitivity are reported with frozen section analysis. The risk of abandoning a planned lung resection and thus creating a gap in operating schedule ranges from 0% to 7%.
COMPLICATIONS
Vascular
Bleeding
Bleeding is the most serious immediate and potentially lethal complication of mediastinoscopy. Some reports state that mortality of massive hemorrhage during mediastinoscopy lies between 15% and 50%. Definition of major hemorrhage is not uniform and this term encompasses blood loss over 500 ccm or the need of additional surgical exploration for definitive control.
Bleeding from large vessels causes practically immediate loss of visual control. The initial maneuver with the scope left in place and slightly parallelly distracted is compression of the bleeding site with a large sponge stick and suction with large-bore tube. Gauze packing takes usually longer than inserting the sponge stick and can be done additionally. However, if no reduction of bleeding is seen, systematic packing must be done; the assistant should hold the scope while operating surgeon inserts the long gauze with a grasper about half the length of the scope at a time while keeping the gauze stretched to avoid its entrapment at the entry into scope (Fig. 4.5). Upon packing the area distal to the scope, the latter can be slightly retracted and the arising free space further packed. Too aggressive packing may enlarge existing lacerations. If the suspected injury is within reach of the finger and probable to originate in a systemic artery, digital compression may be successful for temporary control.
Figure 4.5 Packing—technique of insertion.
Upon achieving temporary control all measures to stabilize the patient’s circulation and preparations for a more extensive procedure are undertaken, that is, volume resuscitation, large-bore venous access (on lower extremity if SVC injury is suspected), ordering of blood units, getting assistance, and preparing the groin for eventual CPB if available. If video footage is available, it can be reviewed to identify the possible source of hemorrhage. Re-exploration may be attempted to locate the injury and apply hemostatic material if deemed sufficient. Success rate of initial packing can be as high as 93%. If bleeding persists and the patient is hemodynamically stable, decision has to be made whether to continue packing and re-explore in 2 days or to perform primary repair. Fibrotic mediastinum is more likely to respond to packing.
Leaving packing in mediastinum and closing the skin wound by suture or foil can be successful in injuries of low pressure and even systemic vessels. The main disadvantage is risk of infection and discomfort for the patient while the outcome remains unclear. Following successful packing, a pseudoaneurysm may develop within weeks. On the other hand, packing may be the ideal option for frail patients with serious comorbidity.
Primary repair is the better option if it allows for planned pulmonary resection or resection is indicated for the diagnosed mediastinal tumor, also if hemothorax develops and if the patient is hemodynamically unstable under packing. Depending on approach chosen, reintubation with double-lumen tube may be needed.
Risk of bleeding is greater in abnormal, fibrotic mediastinum, which can result from previous surgery including mediastinoscopy, induction therapy, and especially radiation.
Prevention of bleeding complications relies on meticulous dissection if adhesions are present, knowledge and respect for normal anatomy and variations including careful study of preoperative contrast CT, mobilization of nodes before applying traction, fine-needle aspiration of potential vessels, gentle moving of the scope and avoidance of tissue impingement between the blades.
The preferred approach if source of bleeding is unknown should be median sternotomy, as it provides access to a major part of mediastinum and can be extended to hemiclamshell incision.
Pulmonary Artery
Main pulmonary arteries can be damaged by direct biopsy, lacerated by traction applied to adherent subcarinal nodes, or by pushing the upper blade of the scope caudally without elevating the artery. Packing is left in place until the suspected site of injury can be reached.
Injury to the right main pulmonary artery is one of the most difficult to manage due to relative inaccessibility of its posterior wall. In patients with resectable right-sided tumors a right thoracotomy provides access to the injury and the possibility to perform resection. Similarly, an injured segmental artery can be either repaired or transected in the process of an upper lobectomy. Central location of the laceration requires pericardiotomy medially to SVC with medial retraction of ascending aorta and lateral retraction of SVC (Fig. 4.6). Encircling of right main pulmonary artery and subsequent application of a tourniquet can be done after division of the serous pericardium on the dorsal aspect (one-fifth of the circumference). Alternatively, compression with a sponge clamp may suffice to achieve central control. Posterior aspect of the right main pulmonary artery is then accessed along the anterior surface of the right main bronchus and bifurcation. One must not forget to control backflow by occluding the artery peripheral to the injury.
Right main pulmonary artery may also be approached lateral to SVC, after dividing the azygos vein and retracting the SVC medially.
Transarterial repair of posterior wall laceration has been described under deep hypothermic circulatory arrest (DHCA), with transection and reanastomosis of the ascending aorta. Such extensive approach with DHCA may be the only option if the bifurcation of the main pulmonary trunk has been torn on the dorsal aspect.
Figure 4.6 Intrapericardial exposure of the central part of the right main pulmonary artery for hemorrhage control.
Thoracotomy may be extended to hemiclamshell incision if necessary. Identically, if median sternotomy was chosen as the initial approach, it may as well be extended to provide better access. Median sternotomy is a better initial choice if a left-sided or no lung tumor is present.
Access to the central left pulmonary artery should be sufficient via left thoracotomy. Transection of ligamentum arteriosum Botalli can improve exposure.
In case a punch biopsy of the artery caused the bleeding, simple withdrawal of the scope and compression of the neck wound for 10 minutes and observation of hemodynamic parameters may suffice. However, such selftamponade only works if the anatomical boundaries of the explored part of mediastinum (mediastinal pleurae, pericardium) are not disrupted.
Systemic Arteries
Innominate Artery and Common Carotid Arteries
The innominate artery is predisposed to injuries because of its intimate relation to the mediastinoscopist’s working channel. Protected by the pretracheal fascia during properly done first mediastinoscopy, it is vulnerable to finger, scope, suction electrode, or even biopsy forceps when the wrong plane is entered or adhesions at remediastinoscopy are present. A high-riding innominate artery can be injured in jugulum while splitting the strap muscles; therefore, palpation is recommended before this maneuver.
The surgeon usually experiences a sudden and quite terrifying gush of blood jetting out of the scope or out of the neck wound. A finger inserted in the wound can follow the current and obliterate, at least partially, the opening in the artery. Unless a high-riding artery is injured, no direct clamping or suture must be attempted as this may lead to further worsening of the situation by enlarging the original tear or creating new ones along the course of the vessel. Median sternotomy with the finger still held in place allows rapid identification of left innominate vein, its isolation and retraction, and identification of the bleeding innominate artery. If sternotomy is considered too risky in patients after CABG, resection of the manubrium may be sufficient for exposure. Further assessment of the situation follows after clamping the artery proximal and distal to the injury. Direct suture, patch plasty, or vascular prosthesis implantation are the options depending on the extent of injury. Injuries located more distally may require reconstruction of the bifurcation of the innominate artery, by anastomosing the prosthesis end-to-end with the subclavian artery and anastomosing the right common carotid to the side of the prosthesis.
If hemostasis cannot be adequately achieved due to presence of infiltrating tumor or if there is no visible backflow from the periphery of common carotid, cardiopulmonary bypass with groin vessel cannulation and deep hypothermia for cerebral protection are needed. An even more precarious situation may arise if the innominate artery is damaged in patients with Bovine arch anatomy (i.e., left common carotid artery arising from the innominate artery) present in 7% to 27% of aortic vasculatures.
Aortic Arch
Access to posterior aspect of the ascending aorta or posteromedial aspect of the aortic arch and suture of lacerations with pledgets mostly requires CPB and hypothermia. So do complete or near-complete avulsions of aortic arch arteries.
Bronchial Artery
Most frequently the bronchial arteries follow the posterior aspects of the main bronchi.
Accessory bronchial arteries present in as many as 26% of patients can be numerous and originate ectopically from the concavity of the aortic arch, left subclavian artery, or lower third of thoracic aorta.
These arteries may be encountered during mediastinoscopy along the anterior wall of trachea and also further distally crossing the proximal left main bronchus anteriorly and supplying the subcarinal or peritracheal lymph nodes. When visible in the subcarinal region, the accessory bronchial artery may be clipped (major bronchial flow is mostly provided via “standard” arteries) before biopsying the nodes.
Avulsion of the artery from the concavity of the aortic arch during sampling of 4L nodes can cause arterial bleeding controllable by packing with hemostatic material; however, a pseudoaneurysm may arise in the later course.
Although not hemodynamically serious, a squirting bronchial artery often causes complete loss of video and quickly fills the narrow space with blood. Applying continuous suction while looking directly through the scope without pulling it out or losing time trying to clean the lens usually leads to identification of the source and exact clipping. Occasionally the bleeding comes from a standard bronchial artery running behind the left main bronchus and across the subcarinal region to the right. Completely disrupting this artery during dissection in the subcarinal region can lead to retraction of its proximal end behind the left main bronchus and difficulties with exact hemostasis.
Systemic Veins
Superior Vena Cava
Posterior and medial aspect of the entire extrapericardial course of the superior cava vein is reachable via mediastinoscopy. Unless adhesions are present, most bleedings occur either after nodal biopsy in this region with avulsion of one of the small veins draining from retrocaval region directly into SVC, or by direct laceration with the superior blade or with coagulation sucker.
Azygos Vein
Azygos vein can be mistaken for a 4R node and biopsied or lacerated during traction of biopsied lymph nodes. With parallelly distracted scope blades, good suction, and compression of the bleeding spot, transcervical application of large clips may be successful. Injuries at the junction with SVC will more likely require repair via thoracotomy.
Airway
Amidst other complications of mediastinoscopy, airway injuries are rather uncommon (2%). Airway may be damaged indirectly by pushing and distracting the scope in tight fibrotic mediastinum or by direct biopsy when mistaken for a fibrotic tumor or node. Upon perforation, there is almost invariably loss of airway pressure and volume return along with a sudden gush of air bubbling out of mediastinum.
Unless the cuff of tracheal tube has been damaged as well, the tube should be repositioned so that its cuff is distal to the perforation.
Small perforations (<5 mm) may be successfully sealed with application of hydroxy-cellulose. Trachea and main bronchi are within good reach of the mediastinoscope and direct transcervical suture of larger lacerations up to 1 cm without loss of tissue should be attempted before embarking on sternotomy or thoracotomy route. This can be accomplished by using a knot pusher with extracorporeal knot tying. The suture can be additionally sealed with fibrin glue.
Nerve Injury
Recurrent Nerves
The left recurrent nerve can be visualized during mediastinoscopy along most of its mediastinal course until it disappears underneath the aortic arch, thus making the nerve vulnerable to direct electrical, thermal, or mechanical injury with the suction electrode or blades of the scope. Such direct injury to the right recurrent nerve is anatomically highly improbable.
Incidence of recurrent nerve palsies is underreported at 0.18% to 3%. Systematic pre- and postoperative laryngoscopy increases the frequency to 6%.
Treatment of mostly temporary LRN pareses is symptomatic and mostly includes absorbable substance injection into vocal cord to achieve medialization. Coagulation within 5 to 10 mm of the left LRN has to be avoided; instead, clips or bipolar devices should be used for hemostasis.
Thoracic Duct Injuries
Six cases of injury to tributaries of the thoracic duct have been described in the literature, manifesting by chylous discharge from mediastinal drain or cervical wound or by chylothorax. The most probable cause was disruption of lymphatic vessels with rarely present insufficient valves during biopsy of 4R and 4L nodes. All chylous leaks stopped with medium chain triglyceride diet.
Esophagus
A rare and potentially life-threatening esophageal perforation after mediastinoscopy occurs in 0.1%. Traction diverticula and age are given credit as predisposing factors.
Typical symptoms and signs of esophageal perforation do not arise unless the mucosa has been perforated, that is, a full-thickness biopsy of the esophageal wall inadvertently taken at the level of left tracheobronchial angle or right paratracheal region. Early diagnosis and active intervention are of paramount importance but cannot guarantee an uncomplicated postoperative course. Early recognition makes primary repair protected by viable tissue flaps highly successful.
Miscellaneous Complications
Pleural Cavity
Perforation of mediastinal pleura is mostly readily recognized and as such does not necessarily represent a complication. Positive airway pressure at the end of the procedure with a transcervically inserted chest tube allows for complete re-expansion of the lung. The tube is either removed at the end of the surgery or left in place until an x-ray is available.
Variants of Mediastinoscopy and Special Situations
Remediastinoscopy
Indications and Contraindications
The most frequent reason for remediastinoscopy is lung cancer restaging after induction treatment. Usually patients undergo invasive restaging when no progressive disease is visible in CT or PET-CT. Other indications include inadequately done first procedure (diagnostic or staging) and lung cancer staging after mediastinoscopy done for benign (sarcoidosis) or other malignant (lymphoma) conditions.
If only nodal sampling was done during previous lung resection for cancer, remediastinoscopy may be indicated in patients with recurrent or metachronous second primary tumors.
All of these indications refer to cervical mediastinoscopy exploring the peritracheal area. To our knowledge there are no reports on redo extended mediastinoscopy in the available English literature.
Contraindications are identical with contraindications for first mediastinoscopy.
Technique
Utilizing the pretracheal fascia for safe entry into mediastinum at the time of the initial mediastinoscopy leads to scarring and adhesion formation between trachea and innominate artery. This major danger point can be avoided either by carefully dissecting the artery from trachea under direct vision or by entering the peritracheal space along the left side of the trachea where the initial dissection is usually not as extensive. After reaching the level of aortic arch, dissection can move further in the pretracheal plane.
The innominate artery safely and gently mobilized away from trachea is less likely to be damaged by indirect traction. Sharp dissection with scissors or low-energy cautery keeping closely to tracheal surface and continuing as far distally as possible is recommended until anatomical landmarks are clear (innominate artery, aortic arch). Cranial traction of trachea by means of a stay suture and good neck extension should facilitate dissection under direct vision, as should sternal traction when available. Adhesions may also have formed between trachea and posterior surface of vena cava or azygos vein; similarly, pericardium with underlying right pulmonary artery may occasionally adhere to carinal area or the right main bronchus. Keeping the meticulous dissection on the side of airway should prevent bleeding incidents. Reaccessing the subcarinal zone may be easier after dissecting along the proximal left main bronchus. Some surgeons may be more comfortable with the slightly narrower and quite shorter classical Carlens mediastinoscope as it may prove nimbler within the tighter mediastinum. However, with adhesions present the procedure has to be done under good visual control, which the videomediastinoscope can sufficiently provide.
Upon safely re-entering mediastinum the procedure should not be particularly difficult. Experienced centers report only a few cases in which remediastinoscopy had to be abandoned for diffuse scarring (“frozen” mediastinum, “preclusive fibrosis”) with 1.8% impossible and 5.2% incomplete procedures in largest published series.
For restaging purposes at least the stations biopsied initially must be reached. If resection is planned in the same session, frozen section analysis is mandatory to exclude patients with persisting nodal disease. It is preferable that remediastinoscopy be done by the same surgeon who performed the initial nodal staging.
Feasibility of remediastinoscopy depends on thoroughness of the initial procedure and applied induction treatment. Concomitant radiotherapy over 60 Gy and time interval over 2 months since completion of induction treatment have been accused of causing more extensive mediastinal scarring than chemotherapy alone.
COMPLICATIONS
The complication rate of remediastinoscopy seems to be slightly higher than that of initial mediastinoscopy in centers performing it on a routine basis. Morbidity ranges from 2.5% in the largest published series to 13% in papers with small number of patients.
The spectrum of complications is naturally influenced by the presence of adhesions and by the fact that dissection closely follows the airway. This results in higher frequency of airway injuries (trachea or right main bronchus laceration), manageable conservatively or with transcervical repair. Almost all published series include patients with postoperative left recurrent nerve paralysis (0% to 1.9%). Other reported complications were biopsy of the lung, puncture of vena cava, chyle leak, biopsy of esophageal musculature, and bleeding from azygos vein. Bleeding complications in fibrotic mediastinum can be mostly well managed by packing alone and do not particularly stand out when compared to first mediastinoscopy. However, one intraoperative death caused by laceration of atheromatous innominate artery at its origin with tamponade and cardiac arrest despite immediate sternotomy has been reported, thus estimating the pooled mortality rate of remediastinoscopy in all published reports to be less than 0.3%, which is similar to first mediastinoscopy.
RESULTS
Negative predictive value (NPV) for postinduction EBUS/EUS can be as high as 85%. Diagnostic accuracy of remediastinoscopy outweighs its technical complexity in experienced centers. Remediastinoscopy offers NPV of 79% to 91% and sensitivity 70% to 83%. The most frequently missed FN nodes are in stations 4L and 7. However, if N2 disease was initially confirmed by EBUS/EUS, a first-time mediastinoscopy may be done for restaging with average 91% NPV.
Mediastinoscopy in Superior Vena Cava Obstruction
SVC obstruction was considered a contraindication for mediastinoscopy in the early reports although evidence was anecdotal. Apart from increased risk of bleeding, brain edema and airway edema requiring tracheostomy used to be listed as potential complications. Currently, 0.4% mortality and 8.1% morbidity are higher than in non-SVC syndrome patients. Major bleeding occurs in 2.5%. Airway obstruction can still occur during induction to anesthesia if no precautions are taken.
Quite frequently the obstructing lesion can be reached rather high in mediastinum and allow sufficient samples to be taken.
Preoperative measures alleviate the symptoms and make the procedure less stressful for the surgeon. Obstructed SVC necessitates venous access on lower extremities. Elevation of upper body reduces the central venous pressure. This can also be rapidly achieved by stenting of SVC. Steroids may also help reducing the head and neck edema although histologic features may be altered especially in lymphomas.
Diagnostic success rates of mediastinoscopy in patients with SVC syndrome are reported between 71% and 100%.
RESULTS
Decades ago, mediastinoscopy has established itself as the most useful technique for staging of mediastinal nodes in terms of accuracy and safety.
Median sensitivity across multiple studies is estimated at 78%; depending on clinical staging it varies between 47% for cN0 and 87% for cN0–3. Overall sensitivity improves to 89% when videomediastinoscopy is evaluated. Negative predictive value of mediastinoscopy has a median of 91%; whereby 42% to 57% of false-negative mediastinoscopies are caused by metastases in nodes not reachable by the technique (stations 5, 6, 8, 9). It does not make much sense to include the 100% positive predictive value and specificity of mediastinoscopy for nodal staging as this is normally not verified by a subsequent thoracotomy (Table 4.1).
Although mortality and morbidity associated with mediastinoscopy reported in large series are low (0% to 0.2%, and 0% to 3.7%), life-threatening complications and death occur even in the most experienced centers.
Among nonsurgical causes of intraoperative mortality cardiac arrest, stroke, and anesthesia in general are reported. Hemorrhage is the most frequent surgical cause of death occurring in up to 0.67% and resulting in death in 0% to 20%. Aortic laceration and injury to proximal right pulmonary artery carry the highest mortality rate among vascular injuries. Patients with known atheromata, vascular aneurysms and anomalies, and with abnormal mediastinum (after induction or previous interventions) may have a higher risk of vascular complications and should be approached with caution.
TABLE 4.1 Sensitivity, Specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of Various Staging Methods
Other important causes of morbidity include recurrent nerve paresis (0% to 1%) permanent in up to 50% of patients, pneumothorax (0% to 0.21%), and airway and esophageal injuries.
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