Mediastinoscopy

Mediastinoscopy

Anesthesia type	GETA
Airway	ETT
Lines and access	large bore PIV x1, +/- A line
Monitors	Standard, BP cuff on left arm, +/- A line
Primary anesthetic considerations
Preoperative	Evaluate for degree of airway compression by mediastinal mass
Intraoperative	Be prepared for major bleeding. Compression to innominate artery may cause R arm BP or A line to falsely display hypotension or cardiac arrest.
Postoperative
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Mediastinoscopy is a procedure that involves a cervical incision and placements of a rigid scope to view and instrument certain structures of the mediastinum. The most common indication for mediastinoscopy is biopsy of mediastinal lymph nodes in N2 or N3 NSCLC, though any indication for biopsy of mediastinal lymph nodes at stations 2, 4 or 7 is possible with this procedure. Mediastinoscopy may also be performed at the thoracic level to access mediastinal lymph nodes at stations 5 and 6 (transthoracic mediastinoscopy, also known as the Chamberlain procedure). Previous mediastinoscopy, innominante or aortic arch aneurysms, and prior chest radiation are relative contraindications to the procedure.

In the more common cervical mediastinoscopy procedure, a cervical incision is made above the sternal notch and a mediastinoscopy is use to bluntly enter and instrument the middle mediastinum. Care is taken to avoid puncturing the numerous vulnerable neurovascular structures in the area (namely the aorta, innominate artery, innominate vein, azygous vein, recurrent laryngeal nerve, right pulmonary artery). Meanwhile, in the classic Chamberlain procedure (transthoracic mediastinoscopy), the 3rd costal cartilage is resected through an incision placed in the left 2nd and 3rd intercostal space, taking care not to injure the internal mammary artery or phrenic nerve, and the mediastinum explored without entering the pleura.

Preoperative management

Patient evaluation

System	Considerations
Cardiovascular	Elderly patients may have comorbid CAD, preop testing to risk stratify is recommended if indicated by history
Pulmonary	Bulky mediastinal lymphadenopathy may make airway management in the anesthetized patient precarious. Ensure that the pt can lie flat without significant airway compression. Patients with lung cancer may develop Lambert-Eaton myasthenic syndrome, quantitative monitoring of neuromuscular blockade is recommended.
Gastrointestinal	Bulky mediastinal lymphadenopathy can cause partial esophageal obstruction, increasing the risk of aspiration
Hematologic	Malignant processes may induce comorbid anemia
Endocrine	Depending on the exact pathology of the anterior mediastinal mass/lymphadenopathy, there may be underlying comorbid thyroid or paraneoplastic syndromes.

Labs and studies

• Preoperative labwork, cardiac studies, and imaging will vary amongst patient populations. As in all cases, much of the preoperative studies will be based on individual patient H&P
• At a minimum, all patients should have a preoperative hemoglobin and type and screen on file prior to case start
• in patients with a history of cardiac disease or low functional status, consider additional cardiac testing with ECG, echo/stress echo. Any reversible ischemia should prompt further cardiac consultation

Operating room setup

• Standard GETA setup
• Risk stratify airway technique to the degree of anticipated airway difficulty and airway compression from mediastinal mass/lymphadenopathy.
• BP cuff on left arm, pulse oximeter on the right arm. The mediastinoscopy may compress the innominate artery which results in reduced/absent right sided upper extremity pulses.
• Arterial line as indicated by history and physical. If placed, it should be right sided, correlating carefully with the left arm BP cuff as right sided pressures may be inaccurate due to great vessel compression by surgeon.
• If CVP/PA catheter are desired, they should be placed through femoral access if SVC syndrome is present.

Patient preparation and premedication

• Avoid premedicating with sedating medications if airway compromise from mass compression is a concern
• If awake fiberoptic intubation is planned, ample time should be allocated for administration of antisialogogue and topicalization of the airway

Regional and neuraxial techniques

• Epidural placement for postop analgesia is typically not indicated given small incision. Epidurals or peripheral nerve blocks may be placed post op if there is catastrophic conversion to median sternotomy or thoracotomy.

Intraoperative management

Monitoring and access

• standard ASA monitors
• 5 lead EKG

• 1 large bore IV (14-16g)
• +/- arterial line
• ensure blood in OR in case of severe bleeding

Induction and airway management

• Standard induction if there are no risk factors for aspiration, otherwise RSI w/ cricoid pressure
• Airway management based off of anticipated risk of difficult intubation based off of patient's pathology, history and physical, and imaging.

Positioning

• Supine, 180˚ degree flip, head toward surgeon.
• often some degree of reverse Trendelenburg (head up) is requested

Maintenance and surgical considerations

• standard maintenance with volatile and/or intravenous agents

Emergence

• extubation is anticipated, extubation strategy based off of difficulty of airway and degree of mediastinal mass airway obstruction.
• normal PONV prophylaxis based off of Apfel score.

Postoperative management

Disposition

• PACU -> home vs surgical ward
• cervical mediastinoscopy is typically an outpatient surgical procedure
• transthoracic mediastinoscopy without violation of the pleura can be same-day discharge; if the pleura is entered a chest tube is placed and the patient is typically observed overnight.

Pain management

• Significant pain is not anticipated: multimodal pain control, typically with short course of oral opioids

Potential complications

• Major bleeding is the most common complication (0.1-0.6%), though most bleeding can be dealt with packing. Instrumentation near lymph node station 4R is the most common site of major bleeding due to injury to the azygous vien. In severe instances, median sternotomy with possible CPB may be necessary to achieve hemostasis and repair vascular injuries.
• pneumothorax
• phrenic or recurrent laryngeal nerve damage (occurs most commonly with manipulation at station 4L)
• tracheomalacia (more often seen in patients with longstanding mediastinal masses)
• esophageal perforation (near lymph node station 7)