Anesthesia for Thoracic Surgery

Establishing One-Lung Ventilation

• A left-sided DLT can be used for most procedures, with the exception of left main bronchus distortion by intra- or extrabronchial mass, compression of left main bronchus by aortic aneurysm, left-sided pneumonectomy, and left sleeve resection.

• DLT placement is facilitated by a Mac laryngoscope with the tip of the DLT anterior until after the vocal cords are passed, at which point a 90-degree rotation is performed and the DLT is inserted until resistance is met (average, 29 cm at teeth). Placement should be confirmed by a fiberoptic bronchoscope.

• DLT complications include hypoxia from malposition, traumatic laryngitis, tracheobronchial rupture from placement trauma or overinflation of bronchial cuff, and inadvertent suturing of DLT to a bronchus.

• Single-lumen tubes can be used with bronchial blockers to achieve OLV. Bronchial blockers are placed with a fiberoptic bronchoscope. The main advantages compared with DLTs are lack of need for reintubation for postoperative ventilation and ability to place in already intubated patients without need for reintubation. The main disadvantage is that the blocked lung deflates slowly.

• Single-lumen bronchial tubes are now rarely used.

• In an emergency, a regular single-lumen endotracheal tube (ETT) can be used as a bronchial blocker by blind advancement into the right mainstem bronchus. Reliable placement into the left mainstem bronchus requires bronchoscopic guidance.

Intraoperative Management of One-Lung Ventilation

• FiO₂ should be titrated down from 100% with a goal of maintaining SpO₂ above 90%.

• Pressure-control ventilation may reduce risk of barotraumas by limiting peak airway pressure.

Hypoxemia During OLV:

1. Verify appropriate placement of DLT using fiberoptic bronchoscopy and clear secretions.

2. Increase FiO₂ to 100%.

3. Recruitment of dependent lung may decrease atelectasis and improve shunt.

4. Optimize positive end-expiratory pressure (PEEP) of dependent lung.

5. Verify adequate cardiac output and oxygen carrying capacity.

6. Apply continuous positive airway pressure (CPAP) or blow-by O₂ to operative lung while in communication with surgical team.

7. Reestablish two-lung ventilation. During pneumonectomy, consider pulmonary artery clamp placement.

8. Evaluate for the possibility of pneumothorax on the dependent side.

Alternatives to OLV:

1. Intermittent apnea after establishing 100% oxygen insufflation.

2. High-frequency jet ventilation.

Pulmonary Tumors

• These tumors present with cough, hemoptysis, dyspnea, wheezing, weight loss, fever, pleuritic chest pain (pleural extension), postobstructive pneumonias, hoarseness (mediastinal involvement), pericardial effusion (cardiac involvement), Horner syndrome (sympathetic chain involvement), dysphagia (esophagus compression), or superior vena cava (SVC) syndrome (SVC compression).

• Paraneoplastic syndromes from lung carcinoma have variable presentation, including Lambert-Eaton syndrome, Cushing syndrome, and hypertrophic osteoarthropathy, among others.

• Benign tumors are most commonly hamartomas but also include bronchial adenomas and pulmonary carcinoids (carcinoid syndrome is uncommon). Malignant tumors are divided to small cell and non–small cell carcinomas (squamous cell, adenocarcinomas, large cell carcinomas). All of these types occur in smokers; adenocarcinomas also occur in nonsmokers.

• Treatment includes surgery, radiation, and chemotherapy.

• Resectability is determined by the anatomic stage of the tumor, but operability depends on the extent of the procedure and the physiological status of the patient.

• Staging is performed by bronchoscopy, computed tomography (CT), and mediastinoscopy. Surgical options include wedge resection, lobectomy, sleeve resection, and pneumonectomy. The goal of surgery is for cure while maintaining sufficient residual pulmonary function.

Workup and Indications for Lung Resection

• Operative criteria for lung resection are based on respiratory mechanics, gas exchange, and cardiopulmo-nary interaction.

• V/Q scanning can determine the relative contribution of each lobe to lung function. This information is used with pulmonary function tests (PFTs) and the following calculations:

Postoperative FEV₁ (forced expiratory volume in 1 second) = preoperative FEV₁ × (1 − % Functional lung tissue removed/100)

Postoperative FEV₁ < 40% = Significant morbidity or mortality Postoperative FEV₁ <30% = May need postoperative mechanical ventilation

Postoperative DLCO (diffusing capacity of the lung for carbon monoxide) <40% = Increased postoperative respiratory and cardiac complications

• High-risk patients receive cardiopulmonary evaluation. Patients unable to climb more than two flights of stairs have increased perioperative risk. VO₂ below 10 mL/kg is also associated with an increased risk.

• Infections refractory to antibiotic treatment (cavitary lesions, empyemas) can be treated by lung resection.

• Bronchiectasis resulting in massive hemoptysis can also be treated by lung resection when the disease is localized.

Preoperative Evaluation and Planning

Normal Airway Anatomy:

• Adult trachea length: 11 to 13 cm from cricoid (C6) to bifurcation at carina (T5).

• Right bronchus: Relatively vertical angle from trachea; divides into upper, middle, and lower lobe branches.

• Left bronchus: Relatively horizontal angle; divides into upper and lower lobe branches.

Abnormal airway anatomy can result from thoracic tumors. Tracheal or bronchial deviation can complicate intubation and DLT placement; airway compression can cause difficulty with ventilation after induction.

Review of CT and magnetic resonance imaging (MRI) anatomy can highlight potential problems.

Preoperative preparation includes a plan for airway difficulties and includes DLTs of multiple sizes, a working fiberoptic bronchoscope, an ETT exchanger, and a CPAP circuit.

A large-bore (14- or 16-gauge) intravenous (IV) line is mandatory for thoracic surgery, and an arterial line is indicated for OLV, resection of large tumors, and patients with significant comorbidities. Central venous pressure (CVP) monitoring is desirable for pneumonectomies. Placement of an epidural catheter may be indicated for postoperative analgesia.

Induction of anesthesia is frequently followed by placement of a single-lumen ETT to facilitate bronchos-copy by the surgical team, after which a DLT may be placed for OLV. After the DLT is placed, proper positioning must be confirmed before positioning for surgery.

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