Anesthesiology

Mediastinoscopy

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What the Anesthesiologist Should Know before the Operative Procedure

This is an elective surgical procedure for the purpose of obtaining a tissue diagnosis for a mediastinal mass, typically mediastinal lymphadenopathy. Comorbidities govern the patient-specific problems you will encounter, which typically are associated with lung cancer (the most common diagnosis made), such as hypertension, COPD, CAD, diabetes, and peripheral vascular disease. Perioperative problems include the potential for a mass effect impinging on vascular or airway structures depending on the size and location of the individual mass. This can be typically visualized on the CT scan that all these patients should have. More generally, the proximity of major vascular or airway structures explains the procedure-related complications from inadvertent biopsy of or direct injury with the mediastinoscope to vascular structures leading to sudden, severe bleeding. Airway injury and, rarely, esophageal injury can also result from similar mishaps; thus, a postoperative CXR required to rule out pneumothorax, pneumomediastinum, or subcutaneous emphysema.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

Delay denies diagnosis and therefore treatment options for a tumor, so delays in terms of days are insignificant. Delays of weeks, for example after placement of an intracoronary stent, are undesirable.

This is an elective surgical procedure.

For an elective procedure, potential risk factors for adverse perioperative events should be sought and optimized as possible.

2. Preoperative evaluation

The most common diseases diagnosed by mediastinoscopy include lung cancer and lymphoma. Evidence should be sought for associated comorbid conditions such as impaired pulmonary function resulting from associated pleural effusions, lung parenchymal infiltration by tumor, airway obstruction, or chronic smoking-related COPD or CAD. Lymphoma and other lymphadenopathies can present with grossly enlarged lymph nodes compressing vital structures such as the SVC or airways; more malignant, infiltrative conditions may directly infiltrate these structures, adding the danger of biopsy-related direct injury to compression. Evidence of this is provided by preoperative CT, which should be evaluated by anesthesiologists prior to induction of anesthesia.

Medically unstable conditions warranting further evaluation include obstructive CAD, COPD (acute flare), airway obstruction or SVC syndrome from mediastinal mass effect.

Delaying surgery may be indicated if: patient requires optimization of COPD or has active symptoms of CAD. Balancing the risk of delaying a cancer diagnosis and formulation of a treatment plan with the antiplatelet therapy initiated with intracoronary stent placement (at least a 30-day delay for a bare metal stent, approximately 12-month delay for a drug-eluting stent) should be discussed at length with the oncology and cardiology teams before embarking on coronary angiography. Choice of preoperative versus postoperative timing of revascularization will depend on severity and location of coronary stenoses, estimation of size of threatened myocardial territory, and choice of stent design. A patient planned for subsequent, related procedures, such as lobectomy, are more likely to need preoperative revascularization. Optimization of medical therapy for CAD may be all that is required.

3. What are the implications of co-existing disease on perioperative care?

Perioperative evaluation

History, examination, and pulmonary function tests, if indicated, should be used to determine whether an acute flare of COPD or untreated reversible airways disease is present and amenable to optimizing by a steroid taper or a trial of inhaled bronchodilators and steroids. Stress echocardiography, exercise testing, or stress radionuclide scanning will be required to evaluate for obstructive CAD with subsequent coronary angiography considered as discussed above.

Perioperative risk reduction strategies

These revolve around treatment of coexisting COPD flares or CAD as discussed above. Severe airway or venous obstruction from SVC syndrome may be partially alleviated by a course of corticosteroids.

b. Cardiovascular system

Acute/unstable conditions: Not typically relevant as this is an elective procedure.

Baseline coronary artery disease or cardiac dysfunction - Goals of management: As above, this rests on the diagnosis identified preoperatively and the management plan of medical versus revascularization in conjunction with the urgency to proceed with oncological diagnosis and treatment.

c. Pulmonary

COPD and reactive airway disease (Asthma) is sought at preoperative evaluation and treatment of an acute flare or evaluation for preoperative optimization with bronchodilators or inhaled steroid therapy.

d. Renal-GI:

Routine evaluation of renal and GI systems is performed; in particular, renal dysfunction will affect management of intravenous dye load should coronary angiography be performed, and use of NSAIDs for postoperative analgesia, typically not necessary for mediastinoscopy but more relevant for subsequent pulmonary surgery.

e. Neurologic:

Routine neurological evaluation should seek sensory or motor deficits as clinical evidence of cerebral metastases. Investigation with CT scanning would be indicated but may already have been performed as a screening procedure by the oncology team.

f. Endocrine:

Routine endocrine evaluation is typically limited to screening for diabetes.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Evidence of hematological abnormalities should be sought by preoperative hemoglobin concentration, platelet count prothrombin time, and activated partial thromboplastin time.

4. What are the patient's medications and how should they be managed in the perioperative period?

Medications associated with preexisting conditions typically involve those used for COPD, hypertension, CAD, and diabetes and with the exception of metformin and ACE inhibitors should be given the morning of surgery. Herbal medication that may affect bleeding such as gingko biloba, vitamin E, or fish oils should be held for 48 hours prior to surgery.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

N/A

i. What should be recommended with regard to continuation of medications taken chronically?

Chronic medications should be continued as indicated for diseases in the following organ systems (cardiac, pulmonary, renal, neurologic, antiplatelet, and psychiatric). Antiplatelet drugs should only be continued if indicated for the treatment of CAD. Anticoagulant drugs may be bridged with heparin is clinically indicated but this must be discontinued prior to surgery recommending over 8 hours for unfractionated heparin and 24 hours for low molecular weight heparin.

j. How To modify care for patients with known allergies -

Latex allergy should be sought and dealt with as indicated below.

k. Latex allergy- If the patient has a sensitivity to latex (eg. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

If the patient has a sensitivity to latex (e.g., rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

l. Does the patient have any antibiotic allergies- - Common antibiotic allergies and alternative antibiotics]

Coverage of typical skin flora is required for this procedure using cefazolin 1-2 grams within 1 hour of incision. A single dose is sufficient for uncomplicated cases. If allergic to cephalosporins or a severe penicillin allergy, clindamycin 600-900 mg is an alternative.

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia

Documented: Avoid all trigger agents such as succinylcholine and inhalational agents:

  1. Proposed general anesthetic plan:

  2. Ensure MH cart available: [- MH protocol]

  3. Family history or risk factors for MH:

Local anesthetics/muscle relaxants

Local anesthetics can easily be avoided by using a small-bore IV line for administration of sedation and analgesia if other lines are required pre induction for example if a large, compressive mediastinal mass is present. If there is suspicion of a thymoma with symptoms consistent with myasthenia gravis, muscle relaxants, magnesium, calcium channel blockers and beta blockers should be avoided and a more exhaustive list of medications contraindicated in myasthenia sought preoperatively.

5. What laboratory tests should be obtained and has everything been reviewed?

Common laboratory normal values will be same for all procedures, with a difference by age and gender as indicated by the local laboratory.

Hemoglobin levels:

Anemia would be an indication for cross-matching packed red blood cells prior to procedure. Commonly, normal or high hemoglobin levels associated with COPD are seen with the common indication of lung cancer. For hematological malignancies, anemia is more common.

Electrolytes:

Medication-related electrolyte abnormalities or renal dysfunction should be sought.

Coagulation panel:

In the absence of anticoagulant medications or significant hepatic disease these ought to be normal but given the risk of major bleeding are required preoperatively. Coumadin or dabigatran effect should be confirmed to have dissipated using prothrombin time and, ideally, thrombin time respectively.

Imaging:

CT imaging of chest should be reviewed for compression of major structures by a mediastinal mass; this will typically have been performed by the oncology team prior to preoperative screening.

Other tests:

Pulmonary function tests as indicated by patient's functional status, should optimization with bronchodilators or steroids be anticipated.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

General anesthesia is required with endotracheal intubation and paralysis due to the proximity of vital structures; movement or bucking during the procedure would be hazardous. Induction of anesthesia may need to be inhalational or an awake fiberoptic technique in the setting of compression/distortion of major vascular structures and airway, respectively. Intravenous ketamine is also an option in the former situation.

6. What is the author's preferred method of anesthesia technique and why?

Coverage of typical skin flora is required for this procedure using cefazolin 1-2 grams within 1 hour of incision. A single dose is sufficient for uncomplicated cases. If allergic to cephalosporins or a severe penicillin allergy, clindamycin 600-900 mg is an alternative.

What do I need to know about the surgical technique to optimize my anesthetic care?

As illustrated by the figures, the mediastinoscope passes close to numerous vital structures with the great vessels presenting the most immediate, catastrophic threat. To access certain levels of mediastinal lymph nodes, a small anterior thoracotomy (Chamberlain procedure) or a video-assisted thoracoscopy (VATS) approach may be used.

As detailed in Figure 1, level L2 lymph nodes are superior to the innominate artery in a paratracheal location, L3 lymph nodes are anterior to the trachea with 3A close to the left carotid artery (Figure 2), L4 nodes are inferior to the innominate artery in paratracheal locations, L5 and L6 are accessible from Chamberlain but now done by VATS, L7 subcarinal. Biopsy of L4R is hazardous for injury to the azygous vein Figure or SVC (Figure 4), L4L aorta (Figures 4, 5, and 6), and L7 the right pulmonary artery (Figure 7).

Figure 1.

Mediastinal lymph node stations.

Figure 2.

Level 2 and 3

Figure 3.

Level 2 and arch vessels

Figure 4.

Level 4 and great vessels

Figure 5.

Level 4 and aorta

Figure 6.

Level 4 and aortic arch

Figure 7.

Level 7 and right pulmonary artery

What can I do intraoperatively to assist the surgeon and optimize patient care?

Insertion of right radial arterial line will provide an alert that traction or compression on the innominate or subclavian arteries is occurring with modification of the track of the rigid mediastinoscope to avoid, potentially fatal, direct injury or traction-related avulsion. In preparation for such events, adequate, wide-bore intravenous access, a fluid warmer, and an active type-and-screen should be available. Some centers routinely cross-match packed red blood cells; others rely on emergency release blood if a high volume of mediastinoscopies are performed with a rare incidence of vascular injury. The field is prepared and draped to allow for an emergency sternotomy.

What are the most common intraoperative complications and how can they be avoided/treated?

Prioritize them by urgency. Bleeding is the main intraoperative complication specific to mediastinoscopy. Pneumothorax or pneumomediastinum from tracheobronchial or esophageal injuries are also possible.

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

Usual criteria for extubation are followed; care must be taken depending on the severity of preexisting cardiopulmonary disease. Should major bleeding have complicated the case, extubation after a period of stability on the ICU is more appropriate.

c. Postoperative management

What analgesic modalities can I implement?

Pain is not a major problem. This can be considered a surface procedure and short-acting opiates are typically used intraoperatively with local infiltration anesthesia and analgesia with NSAIDs (including acetaminophen) sufficient for postoperative analgesia. Oral formulations of opiates and NSAIDs can be provided for use following discharge.

What level bed acuity is appropriate?

Discharge home after 2-4 hours postoperative recovery is appropriate.

What are common postoperative complications, and ways to prevent and treat them?

Postoperative CXR is required to exclude pneumothorax or pneumomediastinum from tracheobronchial or esophageal injuries, which may present as difficulty breathing, oxygen desaturation, chest pain, or cervical subcutaneous emphysema. Evaluation of these complications may be performed under local anesthesia with sedation but it may be more appropriate to offer general anesthesia to protect the airway and facilitate definitive repair, with the exception of ensuring chest thoracostomy to evacuate a pneumothorax prior to re-inducing general anesthesia.

What's the Evidence?

Albage, A, Henriksson, G, Lindblom, D. "Repair of acute mediastinoscopic injury to the pulmonary artery using an intravascular approach and deep hypothermic circulatory arrest". Interact Cardiovasc Thorac Surg. vol. 3. 2004. pp. 368-9.

De Leyn, P, Lardinois, D, Van Schil, PE, Rami-Porta, R, Passlick, B, Zielinski, M, Waller, DA, Lerut, T, Weder, W. "Ests guidelines for preoperative lymph node staging for non-small cell lung cancer". Eur J Cardiothorac Surg. vol. 32. 2007. pp. 1-8.

Karaiskos, T, Karfis, EA, Tsagaropoulou, I, Drossos, GE. "Total circulatory arrest: A life-saving procedure for mediastinoscopic major hemorrhage". Gen Thorac Cardiovasc Surg. vol. 58. 2010. pp. 577-9.

Karfis, EA, Roustanis, E, Beis, J, Kakadellis, J. "Video-assisted cervical mediastinoscopy: Our seven-year experience". Interact Cardiovasc Thorac Surg. vol. 7. 2008. pp. 1015-8.

Park, BJ, Flores, R, Downey, RJ, Bains, MS, Rusch, VW. "Management of major hemorrhage during mediastinoscopy". J Thorac Cardiovasc Surg. vol. 126. 2003. pp. 726-31.

Peltz, M, Douglass, DS, Meyer, DM, Wait, MA, DiMaio, JM, Ring, WS, Jessen, ME. "Hypothermic circulatory arrest for repair of injuries of the thoracic aorta and great vessels". Interact Cardiovasc Thorac Surg. vol. 5. 2006. pp. 560-5.

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