22 PENETRATING THORACIC TRAUMA
Jeffrey L. Johnson M.D., Ernest E. Moore M.D.

1. How often do patients with penetrating chest wounds need an operation?

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Surprisingly rarely. Most civilian penetrating injuries are from knives and low-energy handguns. Consequently, although injuries to the chest wall and lung are common, the majority of patients can be treated with tube thoracostomy alone. Formal thoracotomy or median sternotomy is required in < 15% of isolated penetrating chest injuries.

2. What are the indications for emergency department thoracotomy (EDT) after penetrating chest wounds?

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Patients who arrive at the emergency department with cardiac activity and have suffered circulatory collapse either en route or in the resuscitation area can benefit from EDT. Unlike blunt injury, a treatable cause is more commonly found after penetrating injury (e.g., pericardial tamponade). EDT results in a survival (and walk out of the hospital) of about 20%.

3. What is the “6-hour rule” for penetrating chest injuries?

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In a patient with a penetrating chest injury, an upright chest radiograph with no evidence of pneumothorax after 6 hours makes the likelihood of delayed pneumothorax or occult injury to an intrathoracic organ vanishingly small. The “6-hour rule” identifies patients who can be safely discharged.

4. How much blood in the pleural space can be reliably detected by chest radiograph?

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250 mL, but the patient must be fully upright in order for 250 mL to blunt the costophrenic angle on radiograph.

5. What are the indications for operation in a stable patient with hemothorax after penetrating chest injury?

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Immediate return of > 1500 mL of blood from the pleural space or ongoing bleeding in excess of 250 mL/h for 3 consecutive hours. Obviously, this also depends on the size of the patient; for example, a football lineman can safely lose more blood than a piccolo player.

6. What is a “clam shell” thoracotomy?

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Bilateral anterolateral thoracotomies with extension across the sternum. This procedure allows rapid access to both pleural spaces, pulmonary hilae, and the mediastinum.

7. What is an open pneumothorax?

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A defect in the chest wall that connects the pleural space with the outside world. A close-range shotgun blast would cause an open pneumothorax.

8. How is an open pneumothorax treated?

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The defect in the chest wall should be covered with an occlusive dressing that is fixed on only three sides. This temporary fix prevents entry of air into the pleural space while allowing egress of air under pressure. A chest tube is then inserted. Formal repair of the chest wall can wait until other significant injuries are excluded.

9. Where is “the box”?

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It is located on the anterior chest between the midclavicular lines from clavicle to costal margin. Penetrating wounds are likely to cause cardiac injury in this region. A typical penetrating cardiac injury has a wound in the box; the heart also can be reached from the root of the neck, axilla, and epigastrium.

10. What is Beck’s triad? How often is it present in patients with tamponade caused by penetrating chest injuries?

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Beck’s triad is hypotension, distended neck veins, and muffled heart tones. These signs are difficult to appreciate in trauma patients (especially muffled heart sounds in a busy and noisy resuscitation room) and are present in only 40% of patients with tamponade from penetrating injuries. The absence of distended neck veins can be explained because most patients have concomitant hypovolemia.
KEY POINTS: INDICATIONS FOR THORACOTOMY WITH PENETRATING CHEST INJURY

1. Unstable patients proceed directly to the operating room after trauma survey, tube thoracostomy placement, and resuscitation.
2. Stable patients receive a tube thoracostomy and observant management; 85% of patients respond to this therapy alone.
3. 15% of patients require operative management, which is indicated if immediate pleurovac output is 1500 mL or if output remains > 250 mL/h for 4 consecutive hours.

11. In a stable patient with suspected penetrating cardiac injury, what is the most important initial study?

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After completion of the primary survey (i.e., airway, breathing, circulation), bedside ultrasonography should be performed. This rapid, sensitive method for detecting pericardial fluid indicates cardiac injury. Initial study results may be negative with only a small effusion; therefore, serial examinations are very important.

12. What is the initial therapeutic maneuver in a patient with a penetrating cardiac wound who is not yet hypotensive?

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Percutaneous pericardial drainage. Early pericardial tamponade does not appear immediately life threatening; however, one of the early effects of tamponade is subendocardial ischemia, which puts the patient at risk for refractory arrhythmias. Immediate decompression of the pericardium ensures safer transport to the operating room for definitive repair.

13. In a penetrating chest wound, how is injury to the diaphragm evaluated?

At end expiration, the dome of the diaphragm reaches the level of the nipples (surprisingly high). Any penetrating injury below the level of the nipples may have an injury to the diaphragm. Diagnostic peritoneal lavage is the preferred initial procedure. Red blood cell counts < 1000/mm3 are negative for injury. Counts > 10,000 are positive for injury; for counts of 1000-10,000, thoracoscopy is indicated to visualize completely the hemidiaphragm at risk.

14. Why is it important to detect a small diaphragmatic laceration?

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Abdominal viscera herniate from the positive-pressure abdominal cavity into the negative-pressure pleural space. The morbidity of a strangulated (dead bowel) diaphragmatic hernia is not trivial, often because of delay in diagnosis.

15. Does a patient with a gunshot wound traversing the mediastinum need an operation?

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No. Surprisingly, not all wounds that pass completely through the mediastinum injure a critical structure. In fact, only one third of patients have an injury that requires exploration. Stable patients should be evaluated with history (odynophagia, hoarseness?), physical examination (deep cervical emphysema, expanding hematoma, pulseless extremity?), angiography, bronchoscopy, and esophagoscopy.

16. Are prophylactic antibiotics warranted to prevent empyema after tube thoracostomy?

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A meta-analysis of currently published randomized studies on prophylactic antibiotics for tube thoracostomy suggests a benefit. The number of doses required is unclear; furthermore, the utility in blunt multisystem injury patients may be questioned because of the risk of emergence of resistance.

17. What is the most important risk factor for posttraumatic empyema?

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Persistent hemothorax. Blood incubated at 37° is an excellent culture medium for bacteria; therefore, expedient evacuation of blood from the pleural space via tube thoracostomy or video-assisted thoracoscopic surgery is central in the management of traumatic hemothorax.

18. What is a bronchovenous air embolism?

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The classic presentation of bronchovenous air embolism is a patient with a penetrating chest injury who arrests after intubation and application of positive-pressure ventilation. The underlying pathophysiology is passage of air under pressure from a lacerated bronchus to an adjacent lacerated pulmonary vein. Air then travels across the lungs to the left side of the heart and into the coronary arteries.

19. How is bronchovenous air embolism diagnosed and treated?

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Diagnosis is based only on the typical history (see question 18). Therapy is directed toward removal of air from the left ventricle and coronary arteries. The procedure includes the Trendelenberg (head down) position with the right side down and immediate thoracotomy and aspiration of the apex of the left ventricle, the aortic root, and occasionally the coronary arteries.

20. What is Hamman’s sign?

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A crunching sound on auscultation of the chest that indicates air in the mediastinum.

21. In a penetrating esophageal injury, where may air be evident on physical examination?

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It may be evident in the deep subcutaneous tissues of the neck. In the upright position, air in the mediastinum dissects into a plane continuous with the deep cervical fascia.

22. How do patients with penetrating tracheobronchial injuries present?

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Patients with lacerations of the trachea and major bronchi present with subcutaneous emphysema, hemoptysis, and dyspnea. Chest radiographs reveal a pneumothorax, pneumomediastinum, or both. After tube thoracostomy, continuous air leak and failure of the lung to reexpand (”dropped lung”) should prompt suspicion of a major bronchial injury.

23. What does a blurry bullet on a chest radiograph indicate?

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It indicates a bullet lodged in the myocardium. Movement of the heart causes the bullet’s image to be blurry on x-ray. Beware the blurry bullet.

References
WEB SITE
http://www.acssurgery.com/abstracts/acs/acs0505.htm

BIBLIOGRAPHY
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