Thoracic surgery

After studying this chapter, the learner will be able to:

• Identify the pertinent anatomy of the thoracic cavity.

• Describe patient positioning for each type of thoracic incision.

• Discuss the setup of water-seal chest drainage.

Long tapered flexible dilator. Some are lighted to be used for transillumination of a tubular anatomic structure such as the esophagus.

Decortication

Stripping adhesions from the surface of the pleura.

Fundus

Domelike top of stomach near where the esophagus inserts.

Lobectomy

Removal of a lobe of the lung.

Mediastinum

Cavity within the chest between the pleura that contains the esophagus, trachea, pericardium, and great vessels.

Pleurodesis

Introduction of a chemical sclerosing agent into the chest. A powdered antibiotic, talc, or caustic chemical is instilled between the parietal and visceral layers of the pleura to fuse them by creating fibrous adhesions. The procedure can utilize dry chemicals or wet paste.

Plication

Systematic rows of sutures that stabilize and secure a muscular region such as the diaphragm.

Pneumonectomy

Removal of a lung.

Poudrage

Full-strength dry powder is placed between pleural tissue layers to create adhesions.

Slurry

A loose, moist paste made of fluid and powdered agent used to intentionally create adhesions between two serous surfaces inside a cavity.

Thoracoscopy

Rigid endoscopic procedure performed by percutaneous puncture of the thorax.

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Anatomy and physiology of the thorax

An essential balance must be maintained between atmospheric pressure outside the chest and internal pressures within the thoracic cavity to sustain the vital function of respiration. Knowledge of the anatomy and physiology of the chest and thoracic cavity is necessary for an understanding of thoracic surgery.

Thoracic cavity

The thorax, or chest, is the portion of the trunk between the neck and the abdomen. The thoracic cavity is divided into right and left pleural compartments separated by the mediastinum, which is a separate enclosed space located centrally. Alterations in pressure affecting one side of the thoracic cavity or the mediastinum cause a positional shift of the other compartments.

The bony framework of the thoracic cavity consists of the sternum and costal cartilage anteriorly, 12 pairs of ribs laterally, and 12 thoracic vertebrae posteriorly, all encased within soft tissue. The framework is bounded superiorly by structures of the lower part of the neck and inferiorly by the diaphragm. Eleven external and internal intercostal muscles, which lie between the ribs, have a corresponding artery, vein, and nerve, which require meticulous dissection to avoid inadvertent injury. The arterial blood supply is derived from the internal thoracic artery and the thoracic aorta. Venous drainage is through the mammary veins anteriorly and the azygos and hemiazygos veins posteriorly.

The first seven ribs articulate anteriorly in the midline with the sternum, which is composed of three parts: the manubrium (superiorly), the gladiolus (medially), and the xiphoid process (inferiorly). Ribs one and two articulate with the clavicle and the manubrium. The manubrium and gladiolus join in a projection referred to as the angle of Lewis, a surgical landmark (Fig. 42-1).

FIG. 42-1 Surgical landmarks of the bony ribcage.

Ribs three through seven articulate with the gladiolus (the main sternal body) via the costal cartilage. The eighth, ninth, and tenth ribs are joined anteriorly to the cartilage of the rib above each; the eleventh and twelfth ribs have no anterior fixation. The surgical incisional lines of direction in Figure 42-2 bilaterally overlie the lobes of the lungs on a vertical axis, with the sternum (gladiolus) as the thoracic reference point.

FIG. 42-2 Surgical landmarks: lines of direction.

The ribs articulate posteriorly with the thoracic vertebrae. The esophagus, trachea, and great vessels leading to and from the neck and arms pass through the small space between the manubrium and the vertebrae. Any structure pushing into this narrow opening (e.g., a mediastinal tumor) may obstruct breathing, venous return from the neck and arms, and swallowing.

Lungs

The lungs lie in the right and left pleural cavities (Fig. 42-3). The main function of these porous, spongy, conical organs is oxygenation of the blood with inspired air and expiration of carbon dioxide. The apex of each extends to the neck; the base rests on the superior surface of the diaphragm.

FIG. 42-3 Respiratory system within thoracic cavity.

The right lung, which has three lobes and an oblique fissure and a straighter bronchus, is larger than the left lung, which has two lobes and a more angled bronchus. Blood supply is derived from the two pulmonary arteries and drains into the four pulmonary veins. Lymphatics drain into the bronchopulmonary nodes and into the thoracic duct. Innervation is through the pulmonary plexuses.

The lungs are enveloped by a serous membrane, referred to as the pleura. The pleura has two layers. The external parietal layer lines the inner surface of the thorax. The inner visceral layer covers the surface of the lung. Small amounts of serous fluid (transudate) are secreted between these layers to allow for smooth interface without friction. Excess inflammation or fluid accumulation causes pain and impaired respiratory effort. If infected, the transudate becomes exudate containing increased numbers of white blood cells. Severe inflammation causes fibrosis and adhesions of the pleural tissues.

The trachea divides at the carina into two main branches—the bronchi—leading to the right and left lungs. The right lung, with three lobes, is wider and broader than the left lung because the liver is positioned beneath the diaphragm directly below the base. The left lung has only two lobes and is thinner, longer, and narrower in shape. It shares space in the left side of the chest with the heart, which rests in an area of the left lung referred to as the cardiac notch (Fig. 42-4).

FIG. 42-4 Location of the lobes of the right and left lungs. Patient positioning will be determined for optimal access of the affected lobes or entire lung.

The bronchopulmonary segments within each lung are wedges of tissue separated by veins and thin connective membrane. Although configuration of the segments differs, and variations in the bronchi and blood vessels exist between the right and left lungs, it is generally accepted that both lungs normally have 10 bronchopulmonary segments. Although not demarcated by surface fissures, these segments represent zones of distribution of the secondary bronchi and may be excised individually when the segment contains a small lesion, thus preserving the uninvolved portion.

Each segmental bronchus subdivides into numerous, increasingly smaller branches that eventually end in terminal bronchioles. These fine tubules invested by smooth muscles can constrict to close off the air passage, as in asthma. The terminal bronchioles give rise to respiratory bronchioles from which arise the alveoli. The approximately 300 million alveoli are the functional units wherein oxygenation takes place at the capillary level.

The hilus of the lung, on the mediastinal surface, is the point of entry for the primary bronchus, nerves, and blood vessels. The right primary bronchus is straighter and is a more direct continuation of the trachea. Arterial supply to the lung tissue is derived from the bronchial arteries. Venous drainage is through the bronchial veins, which empty into the azygos system. The pulmonary veins and arteries to and from the heart provide systemic pulmonary circulation. Innervation of the breathing mechanism is by the autonomic nervous system.

Alterations of intrapleural pressure are of major concern because an uncontrolled opening in the thoracic wall and pressure change can be fatal.⁷ Uncontrolled increased positive pressure in one side causes a collapse of the lung on the other side. Referred to as a mediastinal shift, this reaction occurs with entrance of either air or fluid into the pleural cavity, compressing the opposite lung and causing dyspnea. When the mediastinum has moved its limit, it can no longer accommodate a great pressure change; the lung on the affected side collapses. Air in the pleural space between the parietal and visceral pleurae constitutes pneumothorax. Blood in the pleural space constitutes hemothorax.

A mediastinal shift disturbs heart action and circulation. Changes in pressure balance within the thorax reduce vital capacity—the greatest amount of air that can be exchanged in one breath. Many diseases and conditions alter vital capacity (e.g., anesthesia, thoracic tumors, chest trauma).

Special features of thoracic surgery

Entry into the thoracic cavity can be accompanied by pulmonary distress. Team members especially skilled in meeting emergency situations are essential. Patients require close observation and monitoring because changes may occur rapidly. A pulmonary artery catheter is inserted to monitor pulmonary capillary wedge pressures and arterial blood gases. Equipment for bronchoscopy, esophagoscopy, and mediastinoscopy must be readily available. Other preparations are routinely completed for entry into the chest for intrathoracic procedures:

1. Endotracheal anesthesia permits the lungs to expand and function even when subjected to atmospheric pressure. Administration of anesthesia under controlled positive pressure prevents physiologic imbalance and lung collapse in the presence of controlled pneumothorax. Use of a double-lumen endotracheal tube permits expansion of the unaffected lung and collapse of the lung on the surgical side (Fig. 42-6).

FIG. 42-6 Double-lumen endotracheal tube.

At the conclusion of the surgical procedure, the affected lung is reexpanded by the anesthesia provider, and negative pressure in the chest is restored. Portable chest x-rays may be taken immediately to assess the status of the surgical area, pleural cavities, and lung reexpansion.

2. Instrumentation includes a basic laparotomy setup with the addition of thoracic instruments. These include bone instruments and a power saw (Fig. 42-7 shows rib strippers/rasps, shears, and an approximator/contractor); a large self-retaining chest retractor/rib spreader (Fig. 42-8); bronchus clamps and lung forceps (Fig. 42-9); and long instruments for work in a deep incision. Specialty retractors are used to hold lung tissue and displace the bones of the shoulder girdle (Fig. 42-10).