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The trachea is encircled by 18–22 cartilaginous rings. The cricoid cartilage is the only complete tracheal ring. The remaining rings are incomplete and have a membranous portion posteriorly.

The trachea is vertically mobile. When the neck is extended, one half of the trachea is in the neck; when the neck is flexed, the entire trachea is behind the sternum.

Relationship to other organs

The thyroid isthmus is at the second or third tracheal ring.

The innominate artery crosses the trachea in its midportion.

The aorta arches over the trachea in its distal portion.

The esophagus is posterior to the trachea throughout its course.

Blood supply is segmental and is shared with the esophagus. Blood is supplied by the inferior thyroid artery, the subclavian artery, the superior intercostal artery, the internal mammary artery, the innominate artery, and the bronchial circulation.

B Congenital lesions

Types

Stenosis. The three types of tracheal stenosis are generalized, funnel, and segmental. The bronchi may be small in congenital tracheal stenosis, and an associated pulmonary artery sling, in which the artery tethers the trachea, may be present. Webs may also be present.

Congenital tracheomalacia. Cartilaginous softening is caused by compression of the trachea by vascular rings, which are anomalies of the aortic arch. These anomalies include a double aortic arch, a right arch with a left ligamentum arteriosum, an aberrant subclavian artery, or an aberrant innominate artery. The diameter of the trachea is normal, but the wall is collapsible.

Diagnosis

Signs and symptoms

Inspiratory and expiratory wheezing, or stridor, which may be paroxysmal

Feeding problems

Frequent infections

Diagnostic studies

Air tracheography (tomography)

Bronchoscopy

Angiography to assess vascular anomalies

Treatment

Stenosis and webs are usually treated conservatively because of the difficulty in performing tracheal reconstruction in infants.

A web may be removed endoscopically.

Tracheostomy may be helpful and should be performed in a narrow area to avoid injury to normal parts of the trachea.

Chondromalacia is treated by aortopexy and is performed under bronchoscopic guidance to maximize the tracheal lumen. The patient may still have some airway problems for a period of time postoperatively.

C Neoplasms of the trachea

Types

Primary neoplasms are rare.

Squamous cell carcinomas are the most common neoplasms of the trachea. They may be exophytic, may cause superficial ulceration, or may be multiple lesions with interposed

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areas of normal trachea. The tumor spreads through the regional lymph nodes and by direct extension to mediastinal structures.

Adenoid carcinoma grows slowly and has a prolonged course.

Other primary tracheal neoplasms include carcinosarcomas, pseudosarcomas, mucoepidermoid carcinomas, squamous papillomas, chondromas, and chondrosarcomas.

Secondary tumors to the trachea are usually from the lung, the esophagus, or the thyroid gland.

Diagnosis

Radiographic studies include a chest radiograph, tracheal tomogram, and fluoroscopy for evaluation of the larynx. Instillation of contrast medium is rarely necessary for the evaluation of tracheal tumors.

Bronchoscopy is deferred until the final operation because the biopsy may be hazardous due to bleeding or obstruction of the airway. Frozen section examination is adequate for assessment of the tracheal tumor.

Pulmonary function testing is mandatory if carinal or pulmonary resection is contemplated.

Treatment is by tracheal resection.

Overview

Preoperative antibiotics are selected on the basis of preoperative tracheal cultures.

When there is an airway obstruction, anesthesia should be induced with halothane.

High-frequency ventilation may be helpful, and it may be possible to pass a small tube beside the tumor.

Seminoma

Embryonal cell carcinoma

Teratocarcinoma

Choriocarcinoma

Endodermal sinus tumor

Symptoms include chest pain, cough, and hoarseness caused by invasion of the vagus nerves.

Diagnosis. These tumors are diagnosed by a combination of radiographs and serum tumor markers

(β-human chorionic gonadotropin and α-fetoprotein)

Treatment

Seminomas are treated by complete surgical resection followed by postoperative radiotherapy.

Nonseminomas are treated by combination chemotherapy.

Adjuvant therapy. Seminomas are very radiosensitive, and the other cell types may benefit from chemotherapeutic agents.

B

Visceral compartment lesions are usually cystic. The two most common types are pericardial cysts and bronchogenic cysts.

Pericardial cysts are usually asymptomatic and are seen on a chest radiograph. They are smooth walled and occur most commonly in the cardiodiaphragmatic angle. Surgery is usually done as a diagnostic procedure to identify the lesion.

Bronchogenic cysts generally arise posterior to the carina. They may be asymptomatic, or they may cause pulmonary compression, which can be life threatening, particularly in infancy. The usual treatment is surgical excision.

Ascending aortic aneurysms are also included as middle mediastinal masses due to the location of the great vessels in this compartment.

C

Paravertebral sulcus lesions are neurogenic tumors located in the paravertebral gutter. Approximately 10%–20% are malignant.

Incidence. Seventy -five percent of these neurogenic tumors occur in children younger than 4 years of age. A malignancy is most likely to occur if the tumor begins during childhood.

Histologic types

Neurilemomas, which arise from the Schwann cells of the nerve sheath

Neurofibromas, which can degenerate into neurosarcomas

Neurosarcomas

Ganglioneuromas, which originate from sympathetic ganglia

Neuroblastomas, which also arise from the sympathetic chain. Neuroblastomas may have metastasized to bone, liver, and regional lymph nodes by the time that the diagnosis is made. Also, direct extension to the spinal cord may occur.

Pheochromocytomas occur in the mediastinum, although rarely; they behave similarly to the usual intra - adrenal pheochromocytomas.

Symptoms

Symptoms include chest pain secondary to compression of an intercostal nerve. If the tumor grows intraspinally, it may cause symptoms of spinal cord compression. Rarely, these tumors have an endocrine function and can secrete catecholamines.

The symptoms of neuroblastoma include fever, vomiting, diarrhea, and cough.

Diagnosis is by chest radiograph and CT scan.

Treatment is by surgical excision. Postoperative radiation is helpful in the treatment of malignant tumors.

Chapter 6

Heart

D. Bruce Panasuk

William R. Alex

Richard N. Edie

James S. Gammie

I Acquired Heart Disease

A Overview

Epidemiology

Heart disease is the leading cause of death in North America, responsible for 38% of all deaths. Three million myocardial infarctions are recorded annually in the United States, with an accompanying mortality rate of 10%–15%.

Heart valve disease is less frequent than coronary artery disease but still accounts for significant morbidity and mortality. Surgical interventions for heart valve disease are growing 5% per year, primarily due to the ageing of the population and an increased incidence of aortic stenosis.

Signs and symptoms

Dyspnea is caused by pulmonary congestion, which is the result of increased left atrial pressure.

Peripheral edema may be the result of significant right -sided congestive heart failure.

Chest pain may be caused by angina pectoris, myocardial infarction, pericarditis, aortic dissection, pulmonary infarction, or aortic stenosis.

Palpitations may indicate a serious cardiac arrhythmia.

Hemoptysis may be associated with mitral stenosis or pulmonary infarction.

Syncope may result from mitral stenosis, aortic stenosis, or heart block.

Fatigue is the result of decreased cardiac output.

Physical examination should include:

Blood pressure, which should be measured in both arms and legs

Peripheral pulses. The quality and regularity of pulses are important.

Pulsus parvus et tardus may be seen with aortic stenosis.

A wide pulse pressure with a “water -hammer pulse” is seen with aortic insufficiency

Neck veins. Central venous pressure may be indirectly inferred from the height of the internal jugular vein filling. Jugular venous distention may be caused by cardiac tamponade, tricuspid regurgitation, or right heart failure.

Heart

Inspection and palpation of the precordium

Normally, the apical impulse is appreciated at the midclavicular line, fifth intercostal space. In left ventricular hypertrophy, the apical impulse is increased and displaced laterally.

With right ventricular hypertrophy, a parasternal heave is appreciated.

Thrills from valvular disease may be felt.

Auscultation. The quality of heart tones, type of rhythm, murmurs, rales, and gallops are all important.

Preoperative management

A baseline chest radiograph and electrocardiogram should be obtained.

Echocardiography can define ventricular ejection performance. Color doppler echocardiography can demonstrate valvular stenosis or insufficiency.

Cardiac catheterization remains the gold standard for defining coronary artery anatomy and assessing the presence of coronary artery disease. Right heart catheterization is used to

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determine pulmonary artery pressure, cardiac output, pulmonary capillary wedge pressure, and the presence of left to right shunts (“step up”). Left heart catheterization includes coronary artery angiography and ventriculography (to determine ejection fraction).

Pulmonary function studies are important in patients with known pulmonary disease.

Cardiac arrest

Causes of cardiac arrest include:

Anoxia

Coronary thrombosis

Electrolyte disturbances

Myocardial depressants: anesthetic agents, antiarrhythmic drugs, or digitalis

Conduction disturbances

Vagotonic maneuvers

Immediate cardiopulmonary resuscitation is critical, as brain injury results after 3–4 minutes of diminished perfusion.

Treatment should include the following measures:

Airway: best accomplished by endotracheal intubation

Breathing: ventilatory support with an Ambu -bag or a ventilator

Circulation:

Cardiac massage. Closed -chest cardiac massage is usually appropriate. In the patient with cardiac tamponade, acute volume loss, an unstable sternum, or an open pericardium, open-chest massage is usually required.

Electrical defibrillation should be performed if cardiac arrest is the result of ventricular fibrillation.

Drug therapy. Commonly used agents include:

Epinephrine, for its cardiotonic effect

Calcium, also for its cardiotonic effect

Sodium bicarbonate, to treat associated acidosis

Vasopressor agents, to support blood pressure

Atropine, to reverse bradycardia

Replacement of blood volume , if necessary

Extracorporeal circulation (cardiopulmonary bypass). The rationale for using extracorporeal circulation is to provide the surgeon with a motionless heart and a bloodless field in which to work while simultaneously perfusing the different organ systems with oxygenated blood.

Technique. Blood is drained from the right atrium, passed through an oxygenator and a heat exchanger, and pumped back to the aorta.

Protection of the myocardium during the ischemia induced by the procedure is accomplished by hypothermia and cardioplegia.

Pathophysiologic effects of extracorporeal circulation include:

Widespread total body inflammatory response with initiation of humoral amplification systems, including:

Coagulation cascade

Fibrinolytic system

Complement activation

Kallikrein-kinin system

Release of vasoactive substances