Mediastinoscopy

Introduction

Cancer is the second leading cause of death in the United States; of these, lung cancer is the most common cause in both males and females. Although the lung cancer death rate has declined over the years primarily because of a reduction in smoking, the 5-year relative survival rate remains comparatively low at 19%. Early detection and treatment improves survival rates and can possibly offer a cure depending on the type and extent of lung cancer. Unfortunately, because of the lack of symptoms during the early stage, most lung cancers are diagnosed at advanced stages. Accurate cancer staging plays a crucial role in the prognosis and selection of appropriate treatment modality. ^,

Mediastinoscopy is an invasive diagnostic procedure for mediastinal lesions and is effective in clinically staging lung carcinoma. There are minimal to noninvasive modalities useful in clinical staging, and these have precluded the need for routine tissue confirmation via mediastinoscopy. Nevertheless, the sensitivity and specificity for these procedures are subpar compared with mediastinoscopy, ^, which remains the gold standard ^, because of its reliability. Cervical mediastinoscopy (CM) is the conventional approach; alternatives include a left anterior mediastinoscopy and variations of the CM procedure, such as an extended cervical mediastinoscopy (ECM) and video-assisted mediastinoscopy (VAM).

Patients undergoing mediastinoscopy can pose an unusual and potentially dangerous challenge to anesthesiologists. Anterior mediastinal masses could cause significant cardiopulmonary obstruction, resulting in hemodynamic changes that may become exacerbated during induction and maintenance of general anesthesia. The anesthetic management of anterior mediastinal masses is discussed in Chapter 34. Surgical instrument manipulation can potentially result in ischemia, strokes, arrhythmia, and massive hemorrhage. Therefore it is important to understand the surgical procedure and its implications on the anesthetic management.

Case Presentation

A 69-year-old male with a medical history significant for hypertension, type 2 diabetes mellitus on insulin, and 15 pack-years of active cigarette smoking presented with shortness of breath. He had a normal chest x-ray (CXR). Further workup revealed a right upper lobe pulmonary nodule with spiculate margins on chest computed tomography (CT). Positron-emission tomography (PET) showed avid uptake in the right upper lobe nodule in addition to mediastinal and hilar lymph nodes suspicious for metastatic malignancy. An endobronchial ultrasonographic fine-needle aspiration (EBUS-FNA) procedure was negative for malignancy at the hilar and subcarinal stations (average of 3.5 passes). Because of the high suspicion for malignancy, the patient then presented for a standard CM.

Additional preoperative evaluation revealed mild obstructive lung disease on the pulmonary function test and normal cardiac function on the echocardiogram. Preoperative labs were within normal ranges, including a complete blood count, chemistry, and coagulation.

Case Management

The patient was preoperatively evaluated, confirming the nil per os (NPO) status and a reassuring airway with no signs of airway obstruction. Availability of blood products and appropriate vasoactive medications and setup were confirmed before induction. A five-lead electrocardiogram (ECG) was placed to monitor for arrhythmia and cardiac ischemia. The pulse oximeter was placed on the right hand and the noninvasive blood pressure cuff on the contralateral arm. After obtaining peripheral access and preoxygenation, intravenous induction was commenced, followed by a single lumen endotracheal tube (ETT) intubation. The ETT was securely taped and positioned away from the direction of the anticipated mediastinoscope. Additional vascular access was established with a large bore peripheral intravenous (PIV) line. Anesthesia was maintained with an inhalational volatile agent and paralysis via an intermittent neuromuscular blockade agent titrated by twitch monitor.

During the diagnostic mediastinocopy procedure, desaturation was noted with flattening of the continuous pulse oximeter waveform. Ventilator parameters and hemodynamics remained unchanged and stable. The surgeon was immediately notified, and the mediastinoscope position was readjusted. The pulse oximeter waveform returned to baseline. The patient maintained normal saturations and hemodynamics throughout the procedure. Lymph node biopsies were successfully obtained with minimal bleeding. Seven paratracheal and five subcarinal lymph nodes were obtained and sent for pathology. The right upper lobe nodule was left untouched. Hemostasis was ensured with assistance of cautery as the mediastinoscope was slowly withdrawn. The incision was subsequently sutured closed. A sterile bandage was applied. The head of the bed was then rotated back to the anesthesiologist for emergence.

After meeting extubation criteria, the patient was successfully extubated and transported to the recovery room for continuous perioperative monitoring, specifically assessing for any hoarseness, stridor, shortness of breath, neurologic changes, and bleeding. He remained neurologically intact postoperatively and reported minimal pain at the incision site. In addition, there was no pneumothorax on his postoperative CXR. After an uneventful postoperative recovery, the patient was discharged to the inpatient floor.

Review of Literature

Indications

According to the guidelines from the European Society of Thoracic Surgeons and American College of Chest Physicians, tissue confirmation to assess nodal involvement should be considered for nonsmall cell lung cancer (NSCLC) except in patients with peripheral carcinomas of 3 cm or smaller and no evidence of nodal involvement on diagnostic imaging. Imaging modalities, such as CT and PET, can provide information on the clinical staging of mediastinal masses and help avoid unnecessary procedures and noncurative resections. Minimally invasive diagnostic procedures are often recommended as the first surgical diagnostic tool, if available ^, ; even considering the limitations. Most importantly, the sensitivity of EBUS-FNA and endoscopic ultrasound FNA (EUS-FNA) are 89% and 89%, respectively. Combined, the sensitivity increases to 93%. ^,

Mediastinal lymph nodes can be accessed from the airway or esophagus under real-time ultrasound guidance. ^{, ,} EBUS permits access to the paratracheal, subcarinal, and hilar nodes. Paraesophageal nodes can be accessed through the EUS approach. In contrast, CM is limited to the paratracheal and subcarinal nodes for sampling, and extends to paraaortic nodes in ECM. In addition, minor complication rates occur in less than 1% (vs. 6% in mediastinoscopy). ^, Uncommon major complications include pneumothorax, empyema, and hemopneumomediastinum. Given that endosonography has a similar sensitivity but lower complication risk to that of mediastinoscopy, EBUS-FNA or EUS-FNA is recommended as the first diagnostic and staging approach. The procedure is usually performed under local anesthesia and moderate sedation at an outpatient center. A flexible ultrasonic bronchoscope is inserted through the mouth and into the trachea (EBUS) or the esophagus (EUS) to locations of known nodal stations ( Fig. 35.1 ). Once lymph nodes are detected, transbronchial or transesophageal needle aspiration is performed. Sampling errors may occur if there is a small amount of tumor present in the node, resulting in a false negative. Thus it is common to perform multiple passes through different parts of the node (average of three passes). The negative predictive value (NPV) remains lower than desired in endosonography at 60%. Negative findings should be surgically validated if clinical suspicion remains high. Mediastinoscopy following a negative EBUS/EUS improves overall sensitivity from 85% to 94%, and NPV 93%. The staging algorithm for NSCLC and diagnostic indications is out of the scope of this chapter and is discussed in Chapter 4.

Clinical staging of NSCLC is the most common indication for mediastinoscopy. ^{, ,} This includes obtaining tissue to diagnose the pathology and assess the level of nodal involvement. Mediastinoscopy is recommended if minimally invasive methods, as discussed previously, are negative. It may be the preferred diagnostic tool for central tumors or tumors over 3 cm. It can also be used in the clinical staging of small cell lung carcinoma and other mediastinal malignancies, including mesothelioma. Mediastinoscopy may be combined with other thoracic procedures in the resection of lung carcinoma and radical lymphadenectomy. Contraindications to mediastinoscopy include inaccessible lymph nodes, cervical spine disease (limited neck extension), thoracic aortic aneurysm, prior chest radiation or mediastinoscopy, and superior vena cava (SVC) syndrome, which carries the risk of potential bleeding from an increase in venous pressure.