What are the anesthetic considerations for a patient with a potential for respiratory or cardiac complications undergoing sternotomy for an anterior mediastinal mass?

Anesthetic Management for Sternotomy in Anterior Mediastinal Mass

Preoperative Risk Assessment and Imaging

The most critical preoperative step is CT imaging of the chest to identify the relationship and proximity of the right ventricle, right atrium, aorta, pulmonary artery, or extracardiac conduit to the sternum or anterior chest wall, as repeat sternotomy may be associated with cardiac injury when these structures are closely adherent to the sternum. 1

• Obtain comprehensive chest CT angiography to document the exact anatomical relationship between the mass, great vessels, heart chambers, and the sternum 1
• Assess for tracheal compression >50%, which predicts postoperative complications 2
• Evaluate for pericardial effusion, as its presence is associated with intraoperative complications 2
• Perform pulmonary function testing looking specifically for a mixed obstructive-restrictive pattern, which predicts postoperative complications 2
• Assess for severe preoperative symptoms (orthopnea, stridor, cyanosis, jugular vein distension, superior vena cava syndrome), which predict postoperative complications 2

Preoperative Multidisciplinary Planning

A comprehensive surgical and anesthetic plan must be formulated preoperatively with the surgical team, as cardiopulmonary bypass requires time for implementation and should be considered early with appropriate preparations made prior to anesthesia initiation. 2

• Review prior operative notes when repeat sternotomy is planned, as this provides critical insight into previous adhesions and vascular anatomy 1
• Identify peripheral vascular status (femoral, axillary vessels) via ultrasound, CT, or MRI, as cannulation for cardiopulmonary bypass via these vessels may be necessary 1
• Ensure immediate availability of cardiopulmonary bypass equipment and personnel if the patient has severe symptoms, tracheal compression >50%, or pericardial effusion 2

Airway Management Strategy

For patients at intermediate or high risk (severe symptoms, tracheal compression >50%, pericardial effusion), maintenance of spontaneous ventilation is essential, at least initially, as positive pressure ventilation can precipitate cardiovascular collapse. 2

• Low-risk patients (asymptomatic, no tracheal compression, no pericardial effusion) tolerate conventional general anesthesia with neuromuscular blockade and positive pressure ventilation 2
• For high-risk patients, consider awake nasotracheal intubation with maintenance of spontaneous ventilation 3, 4
• Have equipment immediately available for rigid bronchoscopy and emergency femoral vessel cannulation 4, 2
• Avoid general anesthesia entirely when possible for patients with severe positional symptoms from the anterior mediastinal mass 5

Induction and Maintenance of Anesthesia

Titrate induction agents slowly with multiple small doses, allowing 3-5 minutes between doses to achieve peak CNS effect and minimize oversedation, as rapid administration can precipitate cardiovascular collapse. 6

• Administer midazolam no faster than 1 mg over 2 minutes in patients >60 years or with comorbidities, waiting an additional 2 minutes between each increment 6
• Maintain continuous monitoring with pulse oximetry and electrocardiogram throughout induction and maintenance 6
• Have flumazenil immediately available for reversal of benzodiazepine-induced respiratory depression 6
• Use volatile anesthetic agents (desflurane or sevoflurane) for maintenance of general anesthesia in hemodynamically stable patients at risk for myocardial ischemia 1
• Avoid concomitant use of opioids and benzodiazepines when possible, as this combination results in profound sedation and respiratory depression 6

Positioning and Surgical Access Considerations

Position the patient to optimize surgical access while minimizing compression of cardiovascular structures, recognizing that right-sided heart structures may be enlarged or hypertensive, increasing the potential for injury during sternotomy. 1

• Maintain the patient in a semi-upright position during induction if positional dyspnea is present 3, 4
• Ensure peripheral vascular access is established prior to sternotomy, as femoral cannulation may be required emergently 1
• Have defibrillator pads applied outside the operative field but positioned to allow emergency sternotomy if needed 1

Monitoring Requirements

Continuous monitoring of respiratory and cardiac function with pulse oximetry is mandatory, as hypoventilation, airway obstruction, and apnea can lead to hypoxia and cardiac arrest unless effective countermeasures are taken immediately. 6

• Use transesophageal echocardiography intraoperatively to determine the cause of acute, persistent, and life-threatening hemodynamic abnormalities 1
• Monitor for signs of superior vena cava obstruction or cardiac compression throughout the procedure 4, 2
• Maintain body temperature in a normothermic range throughout the procedure 1

Emergency Preparedness

Have resuscitative drugs, age- and size-appropriate equipment for bag/valve/mask ventilation and intubation, and skilled personnel for airway maintenance immediately available prior to induction. 6

• Ensure cardiopulmonary bypass capability is immediately available for patients with severe symptoms, tracheal compression >50%, or pericardial effusion 4, 2
• Have rigid bronchoscopy equipment immediately available for emergency airway management 4
• Prepare for emergency femoral vessel cannulation if cardiovascular collapse occurs 1, 4

Common Pitfalls to Avoid

• Do not proceed with general anesthesia in patients with severe positional symptoms without first establishing cardiopulmonary bypass capability 5, 2
• Do not administer neuromuscular blocking agents to high-risk patients until the airway is secured and adequate ventilation is confirmed 4, 2
• Do not rely on preoperative flow-volume loops to predict intraoperative risk, as they are not useful in management of these patients 5
• Do not assume cardiopulmonary bypass on "standby" is adequate—it must be fully prepared and ready for immediate implementation before induction 5, 2
• Avoid rapid injection of midazolam in patients with cardiovascular instability, as this precipitates severe hypotension 6