颈的电视纵隔镜用于肺癌分期（图文演示）

中文版：颈的电视纵隔镜用于肺癌分期（中文图文演示）


CERVICAL   VIDEOMEDIASTINOSCOPY   FOR   STAGING   OF   LUNG   CANCER
Authors
P de Leyn, T Lerut
Abstract
The description of the cervical videomediastinoscopy for staging of lung cancer covers all aspects of the surgical procedure used for the management of lung cancer.
Operating room set up, position of patient and equipment, instruments used are thoroughly described. The technical key steps of the surgical procedure are presented in a step by step way: incisions, procedure, benefits/videoscopy, complications.
Consequently, this operating technique is well standardized for the management of this condition.

1. Introduction
The prognosis and treatment of patients with non-small cell lung cancer (NSCLC) mainly depends on the involvement of mediastinal lymph nodes (Shields, 1990). In N0 or N1 disease, surgical resection is indicated. When the ipsilateral mediastinal nodes (N2 disease) or contralateral mediastinal lymph nodes (N3 disease) are involved, induction treatment is given in most centers (Vansteenkiste et al., 1998a). Therefore staging of the mediastinum remains very important in patients with NSCLC.

PET-scan has proven to be highly sensitive in the detection of mediastinal nodes (Vansteenkiste et al., 1998b). In patients with negative PET-scans, no mediastinoscopy is indicated. However, when PET-scan shows N1 or N2-N3 disease or in patients with centrally located tumors, surgical staging with mediastinoscopy is indicated.

2. Anatomy

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The mediastinum extends anteroposteriorly from the sternum to the spine and sagittally from the thoracic inlet to the diaphragm. Its boundaries include:
1. the sternum anteriorly;
2. the thoracic vertebra posteriorly;
3. the first thoracic rib, the first thoracic vertebra, and the manubrium superiorly;
4. the diaphragm inferiorly.

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The anatomy is well defined in the mediastinum, but there is no consensus among thoracic surgeons concerning the actual division of the mediastinum into compartments. An arbitrary division of the mediastinum into compartments is used to identify the origin of abnormalities discovered during a diagnostic evaluation.
The mediastinum may be divided into 4 compartments: superior, middle, anterior, and posterior.
1. The superior mediastinum extends above a line drawn from the manubrium of the sternum through the lower edge of the fourth thoracic vertebral body.
2. The anterior mediastinum lies below the superior compartment, between the sternum and the pericardium.
3. The posterior mediastinum extends behind a coronal plane through the posterior aspect of the pericardium.
4. The middle compartment lies between the anterior and posterior divisions of the mediastinum.

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The superior and middle mediastina contain a large number of structures that can be explored with the mediastinoscope. These structures are usually classified according to their relationship to the trachea, as the surgeon follows its pathway in order to explore the paratracheal areas. They include:
- anterior to the trachea, thyroid isthmus and blood vessels (superior vena cava, pulmonary artery, aortic arch, anterior communicating jugular vein, thyroid veins, and thyroidea ima artery and vein).
1. Thyroid isthmus
2. Superior vena cava
3. Pulmonary artery
4. Aortic arch

- to the right of the trachea, blood vessels (right carotid artery, right subclavian artery, azygos vein, pulmonary artery, and superior division of the right pulmonary artery), nerves (right recurrent laryngeal nerve, vagus nerve), and bronchi (right main bronchus and right upper lobe bronchus).
5. Right subclavian artery
6. Azygos vein
7. Right recurrent laryngeal nerve
8. Right main bronchus

- to the left of the trachea, blood vessels (thoracic duct, aortic arch, bronchial artery, pulmonary arteries), left recurrent laryngeal nerve, esophagus, and left main bronchus.
9. Thoracic duct
10. Left recurrent laryngeal nerve
11. Left main bronchus

- inferior to the trachea, carinal lymph nodes, esophagus, and tracheal bifurcation.
12. Carinal lymph nodes
13. Esophagus
14. Tracheal bifurcation

3. Indications
Indications
1. Preoperative staging of lung cancer when PET is available:
- to confirm N2, N3 disease;
- when PET shows N1 disease;
- in central tumors (even when no nodes are found on PET).
2. Preoperative staging of lung cancer when PET-scan is not available: every patient with NSCLC, except T1N0 squamous cell carcinoma (De Leyn et al., 1997);
3. Diagnosis of enlarged mediastinal nodes;
4. Diagnosis of mediastinal tumoral mass.

Contraindications
- when general anesthesia is contraindicated;
- large goiter;
- patients with tracheostomy;
- extreme kyphosis.

4. Operating room set-up

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Cervical mediastinoscopy is performed under general anesthesia. The endotracheal tube should be positioned at the left corner of the mouth.
The neck is extended and the shoulders are elevated.

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1. The surgeon stands at the patient’s head.
2. The scrub nurse stands on the right side of the patient.
3. The assistant stands on the right side of the patient.
4. Anesthesiologist

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1. Videomediastinoscope with thoracoscopic unit
2. Anesthetic equipment on the left side of the patient
3. Electrocautery
4. Instrument table

5. Incisions

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A 3 cm transverse cervical incision is made approximately one fingerbreadth above the manubrium. The pretracheal muscles are separated vertically in the midline to expose the anterior surface of the trachea. The thyroid isthmus is retracted superiorly and the tracheal surface is exposed just below the isthmus. At this point, one should avoid dissecting downwards into the mediastinum. It is easier to incise the pretracheal fascia just below the isthmus and then to continue the dissection downwards and close to the anterior surface of the trachea.

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The surgeon’s index finger is advanced along the pretracheal plane and the mediastinum is carefully palpated for the presence of nodal disease. This palpation is of extreme importance; pretracheal nodes are more easily palpated than visualized. The finger is withdrawn and the mediastinoscope is advanced.

6. Procedure

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1. Suction catheter
2. Left recurrent laryngeal nerve
3. Azygos vein
4. Right main bronchus
5. Right pulmonary artery
The plane in front of the mediastinoscope is developed with blunt dissection, using a metal sucker through the channel of the mediastinoscope. Small bleeding vessels may be coagulated. One has to be very cautious with coagulation on the left paratracheal side because of the presence of the left recurrent nerve. Bleeding on this side is best handled with a hemostatic gauze introduced through the mediastinoscope. To avoid and to handle major complications, it is important to visualize anatomical landmarks such as the azygos vein, the right and left main bronchus, and the right pulmonary artery before actual biopsies are taken.

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1. Subcarinal nodes
2. Esophagus
To reach the subcarinal space, the scope has to be brought under the right pulmonary artery. After taking biopsies of these subcarinal nodes, the esophagus can be seen and care should be taken not to injure it.

• Bleeding management
When major bleeding occurs, packing is the first thing to do. By packing for at least 10 minutes, even severe bleeding may be stopped. Vascular clips can be easily placed through the mediastinoscope. If packing and vascular clips have no effect, right thoracotomy (for bleeding of the azygos vein, caval vein or right pulmonary artery) or median sternotomy (for bleeding of aorta or innominate artery and vein) is necessary.

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By cervical mediastinoscopy, the following nodal stations (according to the Mountain/Dresler modification (1997) from Naruke/ATS-LCSG Map (Mountain and Dresler, 1997) may be sampled:
- level 1: superior mediastinal lymph nodes;
- level 2L and 2R: left and right upper paratracheal nodes;
- level 4L and 4R: left and right lower paratracheal nodes;
- level 7: subcarinal nodes.

Nodes corresponding to level 8, 9, 5, and 6 cannot be sampled via a standard cervical mediastinoscopy.
- level 8: posterior subcarinal nodes, paraesophageal nodes;
- level 9: inferior pulmonary ligament nodes;
- level 5: subaortic nodes;
- level 6: para-aortic nodes.

7. Benefits/videoscopy
The development of videoscopic and video-assisted technology during recent years has opened up new perspectives in surgical practice.

Advantages
The magnified image on the screen offers a much more detailed image. As a result, a more accurate and extensive dissection is possible. With some experience, the subcarinal nodes can be completely dissected with visualization of the esophagus.
Classic mediastinoscopy is a difficult procedure to teach as the working channel is narrow. With direct and simultaneous video recording on a TV monitor several people can follow the operation; this offers greater teaching capabilities.
In the videomediastinoscope, the light optics are built into the framework of the scope, leaving ample space for other videoscopic instruments. As a result, other thoracoscopic procedures can be performed through this scope (eg, thoracic sympathectomy, dissection of mammary artery for CABG).
Mediastinoscopy is considered a key procedure for the staging of lung cancer. However, there seems to be a great variation in the way biopsies are taken. Videotaping of the surgical procedure may result in more accurate judgements during clinico-pathological discussions. Widespread international use of videotaped mediastinoscopy may lead to better understanding and standardization of this procedure.

8. Complications
Cervical mediastinoscopy is a low-risk procedure. In experienced hands, cervical mediastinoscopy has a morbidity as low as 2.3% (Luke et al., 1986). The most important complication is severe hemorrhage. The incidence of immediate thoracotomy for bleeding varies in the literature between 0.01% and 0.6% (Bacsa et al., 1974; Puhakka, 1989). Other major complications are injury of the esophagus, damage to the recurrent laryngeal nerve (usually the left), and pneumothorax.

Possible complications of mediastinoscopy:
- hemorrhage;
- injury of left recurrent nerve;
- esophageal injury;
- pneumothorax;
- mediastinitis;
- wound infection.

Over a 20-year period, we performed over 4000 cervical mediastinoscopies (De Leyn and Lerut, 2000). There was no hospital mortality. Major bleeding requiring immediate intervention occurred in 4 patients and injury to the esophagus was seen in one patient. In this patient the mediastinum was drained through the mediastinoscopy incision and the fistula dried up after a few days of conservative treatment.

Conclusion
Videomediastinoscopy has significantly improved the results of mediastinoscopy. It remains of key importance in the mediastinal staging of NSCLC.

9. Reference
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