Parasternal Mediastinotomy

Anatomy and Physiology

The mediastinum is the central compartment of the chest, situated between the 2 pleural spaces, and can be divided into 4 sections: the superior, anterior, middle, and posterior mediastinum. The middle mediastinum contains the heart and the roots of the great vessels. The superior mediastinum, located above the heart, includes the aortic arch, the origins of the carotid and subclavian arteries, and the lymph nodes surrounding these vessels.

The anterior mediastinum lies behind the sternum and in front of the pericardium, while the posterior mediastinum is located behind the pericardium and the heart. Access is primarily directed toward the superior and anterior mediastinum in a mediastinotomy. The main focus is on the superior mediastinum, as it contains the aortopulmonary window nodes, peribronchial nodes, and other relevant structures for the procedure.[3][4] 

Structures at risk during this procedure include the aorta, pulmonary artery and vein, and the pericardium. Critical neural structures at risk include the phrenic nerve, which runs medially along the pericardium, and the left recurrent laryngeal nerve, which loops under the aortic arch before ascending into the neck to innervate the vocal cord. Injury to the phrenic nerve can result in an elevated hemidiaphragm on the affected side. In contrast, damage to the recurrent laryngeal nerve can cause hoarseness and paralysis of the vocal cord on the same side.

Indications

The Chamberlain procedure, or parasternal mediastinotomy, is indicated primarily for the biopsy and diagnostic evaluation of inaccessible anterior mediastinal masses and lymph nodes through less invasive methods. Here are the primary indications for this procedure:

• Diagnosis of mediastinal massesThe differential diagnosis for some of these masses and nodes is wide-ranging, including carcinoma, tuberculosis, sarcoidosis, lymphomas, thymomas, and other germ-cell tumors.[2][5]

• Staging of lung cancer

  • The current American and European guidelines for preoperative mediastinal nodal staging in non-small cell lung cancer emphasize achieving the highest level of certainty before proceeding with lung resection. They recommend obtaining tissue confirmation of regional nodal spread in all cases, except for patients with small (less than or equal to 3 cm) peripheral tumors that show no signs of nodal involvement on computed tomography and positron emission tomography (PET) scans. More than 1 cm or "hot" nodes on PET need a pathologic diagnosis. Tissue confirmation can be achieved using either endoscopic or surgical methods.[2] 
  • This technique is used to assess and biopsy lymph nodes in the aortopulmonary window, periaortic area, peribronchial area, and anterior mediastinum. 
  • Results from a study showed that mediastinotomy successfully sampled 1 or more lymph nodes in 67% of patients. Five patients (4.3%) who underwent mediastinotomy were spared a thoracotomy by the identification of metastases to aortopulmonary lymph nodes.[6]

• Inconclusive results from less invasive techniquesWhen endoscopic techniques like EBUS-FNA or EUS-FNA do not provide adequate tissue samples or when their results are inconclusive, mediastinotomy is employed.

• Evaluation of anterior mediastinal lymphadenopathyThis procedure can be used in patients with unexplained anterior mediastinal lymphadenopathy where other diagnostic methods have failed to provide a definitive diagnosis.

   

Contraindications

Contraindications of mediastinotomy include:

• Superior vena cava syndrome
• Previous mediastinal irradiation
• Previous median sternotomy
• Tracheostomy
• Aneurysm of the aortic arch [7]

Equipment

The equipment needed for mediastinotomy includes:

• Mediastinoscope with a light source
• Surgical instruments
  • Scalpels, forceps, scissors, periosteal elevators, bone cutters, sternal retractors, and clamps
• Hemostatic devices
• Blunt dissection tools
  • Includes gauze (to be used with finger dissection) and Kitner dissectors for separating tissues and creating the extrapleural space
• Sutures and needles
• Chest tube and drainage system
  • For managing any pleural openings and preventing pneumothorax

Personnel

One surgeon and 1 assistant usually perform the procedure. The pathologist should be on standby for frozen section analysis to ensure enough tissue has been submitted. An anesthetist is also required, as this procedure is performed under general anesthesia.

Preparation

There is minimal patient preparation for this procedure. Many of these can be done safely as outpatient procedures. The patient should withhold food and fluids after midnight before the operation and present to the preoperative holding area before surgery. In the operating room, after general anesthesia is induced, the entire neck, chest, and upper abdomen should be prepped into the field in case catastrophic bleeding occurs, and emergent median sternotomy or thoracotomy is needed for control of massive bleeding.

Technique or Treatment

The mediastinotomy procedure, specifically an anterior mediastinotomy for biopsy purposes, is performed under general anesthesia with endotracheal intubation. The patient is positioned with a 15-degree elevation of the head of the bed to optimize surgical access. A 3- to 5-cm horizontal incision is made adjacent to the sternum at the second intercostal space, carefully removing cartilage while preserving the perichondrium. The internal thoracic vessels are identified and retracted or ligated to prevent bleeding. The extrapleural space is then opened, followed by blunt dissection to push the pleura away from the mediastinum, thus gaining access to the nodal envelopes of interest.

During the procedure, the surgeon carefully identifies and biopsies the target lymph nodes or masses, recording the stations of the biopsied nodes for pathology. A frozen section is often performed to ensure the adequacy of the tissue samples. If a pleural biopsy is necessary, the pleura is opened, and a small chest tube is placed through a separate stab incision to manage potential air leaks. The wound is then closed in layers, and the Valsalva maneuver is performed to check for air leaks before removing the chest tube. Finally, the patient is awakened and extubated, concluding the procedure.[8][9]

Complications

Potential complications of diagnostic anterior mediastinotomy are rare and occur in less than 1% of patients. These complications include:

• Bleeding from the internal mammary or the other major vessels like the aortic arch in areas of dissection and biopsy
• Chylothorax resulting from injury to the lymphatic duct
• Esophageal perforation
• Wound infection
• Pneumothorax

Injuring mediastinal structures, such as the phrenic, left recurrent laryngeal, vagus nerves, the thoracic duct, and major arteries and veins accessible through this approach, may cause complications.

Clinical Significance

Mediastinal lymphadenopathy is a frequently encountered clinical issue requiring physicians to understand common diagnostic entities' clinical and radiological manifestations. Selecting the appropriate tissue diagnosis modality is crucial, aiming to use the least invasive technique with a good diagnostic yield. Parasternal mediastinotomy involves surgical entry to the mediastinum through an incision in the parasternal second left intercostal space. Although this technique has decreased due to advancements in less invasive methods, it remains highly specific and significant in certain cases.

The primary clinical significance of parasternal mediastinotomy lies in its ability to obtain sufficient viable tissue for histologic confirmation of diagnoses or cultures in cases of infection. This is particularly important for accurately staging lung carcinoma with aortopulmonary window node involvement or enlargement. EBUS-FNA and EUS-FNA have largely replaced mediastinotomy; when lymph nodes are accessible, they are significantly less invasive and allow for taking samples from more lymph node stations.[10] Despite this, mediastinotomy remains invaluable when these less invasive methods are inadequate. Ultimately, obtaining an accurate diagnosis through any modality leads to favorable treatment outcomes, highlighting the enduring importance of parasternal mediastinotomy in thoracic surgery.[11][12]

Enhancing Healthcare Team Outcomes

Effective patient-centered care for parasternal mediastinotomy requires a coordinated effort from a multidisciplinary team. Surgeons must possess advanced surgical skills and a deep understanding of thoracic anatomy to perform the procedure safely and accurately. Advanced clinicians, such as nurse practitioners and physician assistants, play a critical role in preoperative assessment, patient education, and postoperative care, ensuring that patients are well-informed and prepared for surgery and recovery. Nurses are essential for providing perioperative care, monitoring vital signs, managing pain, and addressing immediate postoperative needs. Pharmacists contribute by managing medications, including anesthesia and pain management protocols, to optimize patient safety and outcomes.

Interprofessional communication is paramount to enhance team performance and patient outcomes. Regular multidisciplinary meetings and clear, consistent communication channels help ensure that all team members are informed about the patient’s status and care plan. Care coordination involves collaborating with radiologists to accurately interpret imaging studies and pathologists to confirm tissue diagnosis, ensuring the surgical decision-making process is well-informed. This collaborative approach enables timely and accurate diagnosis, appropriate surgical intervention, and comprehensive postoperative care, ultimately improving patient safety, reducing complications, and enhancing overall outcomes for patients undergoing parasternal mediastinotomy.