Chapter 24

• During one-lung ventilation, the mixing of unoxygenated blood from the collapsed upper lung with oxygenated blood from the still-ventilated dependent lung widens the Pa–a (alveolar-to-arterial) O2 gradient and often results in hypoxemia.
• Malpositioning of a double-lumen tube is usually indicated by poor lung compliance and low exhaled tidal volume.
• If epidural opioids are to be used postoperatively, their intravenous use should be limited during surgery to prevent excessive postoperative respiratory depression.
• Postoperative hemorrhage complicates about 3% of thoracotomies and may be associated with up to 20% mortality. Signs of hemorrhage include increased chest tube drainage (> 200 mL/h), hypotension, tachycardia, and a falling hematocrit.
• Bronchopleural fistula presents as a sudden large air leak from the chest tube that may be associated with an increasing pneumothorax and partial lung collapse.
• Acute herniation of the heart into the operative hemithorax can occur through the pericardial defect that is left following a radical pneumonectomy.
• Nitrous oxide is contraindicated in patients with cysts or bullae because it can expand the air space and cause rupture. The latter may be signaled by sudden hypotension, bronchospasm, or an abrupt rise in peak inflation pressure and requires immediate placement of a chest tube.
• Following transplantation, peak inspiratory pressures should be maintained at the minimum pressure compatible with good lung expansion, and the inspired oxygen concentration should be maintained at < 60%.
• Regardless of the procedure, the major anesthetic consideration for patients with esophageal disease is the risk of pulmonary aspiration.
• During the transhiatal approach to esophagectomy, substernal and diaphragmatic retractors can interfere with cardiac function.

Indications and techniques for thoracic surgery have continually evolved since its origins. Common indications are no longer restricted to complications of tuberculosis and suppurative pneumonitis but now include thoracic malignancies (mainly of the lungs and esophagus), chest trauma, esophageal disease, and mediastinal tumors. Diagnostic procedures such as bronchoscopy, mediastinoscopy, and open-lung biopsies are also common. Anesthetic techniques for separating the ventilation to each lung have allowed the refinement of surgical techniques to the point that many procedures are increasingly performed thoracoscopically. High-frequency jet ventilation and cardiopulmonary bypass (CPB) now allow complex procedures such as tracheal resection and lung transplantation, respectively, to be performed. Anesthetic management of cardiac surgery and anesthesia for thoracic aortic aneurysms are discussed in Chapter 21; anesthesia for thoracic trauma is reviewed in Chapter 41.

Thoracic surgery presents a unique set of physiological problems for the anesthesiologist that requires special consideration. These include physiological derangements caused by placing the patient with one side down (lateral decubitus position), opening the chest (open pneumothorax), and the frequent need for one-lung ventilation.

### The Lateral Decubitus Position

The lateral decubitus position provides optimal access for most operations on the lungs, pleura, esophagus, the great vessels, other mediastinal structures, and vertebrae. Unfortunately, this position may significantly alter the normal pulmonary ventilation/perfusion relationships (see Chapter 22). These derangements are further accentuated by induction of anesthesia, ...

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