Pulmonary contusions, defined as direct injury to the lung resulting in both hemorrhage and edema in the absence of a pulmonary laceration, are a source of severe morbidity and mortality following penetrating and blunt trauma. CT has shown this entity to be much more prevalent than previously recognized.4 The most common cause of pulmonary contusions is a compression-decompression injury to the chest, such as seen in high-speed motor vehicle crashes.
There are two stages in the pathophysiology of pulmonary contusions. First, there is direct injury to lung parenchyma. Second, resuscitative measures, particularly IV crystalloid fluid administration directed at restoring intravascular volume loss due to hemorrhage, can precipitate cardiopulmonary decompensation. Fluid resuscitation in the setting of unilateral pulmonary contusion can cause extravasation of fluid into the contralateral (uninjured) lung. Increased capillary hydrostatic pressures result in leakage of blood and fluid into the interstitium and alveoli. Unfortunately, the process is self-perpetuating; as each proximate segment of lung sees the full force of the right heart activity, it becomes functionally congested and contused, and the process continues to the next uninjured segment of lung. This process results in increased intrapulmonary shunting and resistance to airflow, decreased lung elasticity, and increased work of breathing, leading to hypoxia, hypercarbia, and respiratory acidosis. Cardiopulmonary decompensation may quickly ensue.
Chest pain, tachypnea, chest wall contusions, and hypoxia suggest underlying pulmonary contusion. Physical examination may reveal decreased or coarse breath sounds over the affected lung field. Chest radiograph and CT may show patchy, ground-glass opacities in mild or moderate contusion and widespread consolidation in severe contusion.5 Contusions are found in nonsegmental areas of the lung and across pleural fissures. Radiographic findings of pulmonary contusion may mimic those associated with aspiration pneumonia and fat embolism, but these entities are typically not seen for 12 to 24 hours and usually have a segmental distribution. Areas of lung opacification on chest imaging within 6 hours of blunt trauma are usually considered diagnostic of pulmonary contusion (Figure 261-7). CT is more sensitive for the detection of pulmonary contusions than plain radiographs, with as many as 70% of pulmonary contusions not visible on the initial radiograph.4 In addition to the high diagnostic rate of CT scan for pulmonary contusion, it may also be possible to anticipate complications such as acute lung injury (also known as acute respiratory distress syndrome or noncardiogenic pulmonary edema), depending on the extent of the pulmonary contusion. Patients who have a contusion >20% of lung volume have up to an 80% risk of developing acute lung injury.24
Pulmonary contusion. A. Chest radiograph shows pulmonary contusion from blunt chest trauma, along with 9th and 10th rib fractures. B. CT shows pulmonary contusions on the anterior part of the right lung and a sternal fracture with mediastinal hematoma.
Treatment primarily involves maintenance of adequate ventilation and pain control. Epidural analgesia is the preferred method of pain control; however, consider intercostal nerve blocks and paravertebral analgesia when an epidural is contraindicated.25 The volume of contused lung influences the need for mechanical ventilation. Patients with less than one fourth of total lung volume involvement (about one lobe) usually do not require such support. If ventilatory assistance is required, avoid overinflation of normal alveoli. Placing the noninjured lung dependent by turning the patient to the decubitus position may improve ventilation–perfusion matching. Patients with extensive pulmonary contusion may be candidates for high-frequency oscillatory ventilation, a technique that can improve oxygenation, although it may not improve survival.26 Guidelines for the management of pulmonary contusion and flail chest are listed in Table 261-4.25
TABLE 261-4Eastern Association for Surgery of Trauma Practice Management Guideline for Pulmonary Contusion—Flail Chest ||Download (.pdf) TABLE 261-4 Eastern Association for Surgery of Trauma Practice Management Guideline for Pulmonary Contusion—Flail Chest
|Level 1 recommendations (convincingly justifiable based on the available scientific information alone) ||None. |
|Level 2 recommendations (reasonably justifiable by available scientific evidence and strongly supported by expert opinion) || |
Unnecessary fluid administration should be meticulously avoided; a pulmonary artery catheter may be useful to avoid fluid overload.
Obligatory mechanical ventilation should be avoided.
The use of optimal analgesia and aggressive chest physiotherapy should be applied to minimize the likelihood of respiratory failure and ensuing ventilatory support.
Patients with pulmonary contusion requiring mechanical ventilation should be weaned from the ventilator at the earliest possible time.
Positive end-expiratory pressure/continuous positive airway pressures should be included in the ventilatory regimen.
Steroids should not be used in the therapy of pulmonary contusion.
|Level 3 recommendations (supported by available data but adequate scientific evidence is lacking) || |
A trial of mask continuous positive airway pressure should be considered in alert, compliant patients with marginal respiratory status.
Independent lung ventilation may be considered in severe unilateral pulmonary contusion.
Diuretics may be used in the setting of hydrostatic fluid overload as evidenced by elevated pulmonary capillary wedge pressures in hemodynamically stable patients or in the setting of known concurrent congestive heart failure.
Surgical repair may be considered in severe unilateral flail chest or in patients requiring mechanical ventilation when thoracotomy is otherwise required.
Patients with severe unilateral lung injury who are not responding to conventional mechanical ventilation may benefit from synchronous independent lung ventilation provided through a double-lumen endobronchial catheter. This technique helps prevent overinflation of the normal lung and underinflation of the damaged, poorly compliant lung.
Bleeding from direct lung injury is the most common cause of hemothorax. The compressing effect of the blood within the pleural space, high concentration of lung thromboplastin, and low pulmonary arterial pressure help limit bleeding as a result of torn lung parenchyma. Bleeding into the hemithorax may arise from mediastinal, diaphragmatic, pulmonary, pleural, chest wall, or even abdominal injuries. Bleeding of venous origin usually tamponades without intervention. Damage to intercostal or internal mammary arteries or pulmonary vessels causes more severe bleeding and almost always requires invasive management.
Evacuate hemothoraces of >300 to 500 mL expeditiously to avoid complications. Large clots in the pleural space can act as a local anticoagulant by releasing fibrinolysins from their surface. Bleeding from multiple small intrathoracic vessels often stops fairly rapidly after the hemothorax is completely evacuated.
Fluid collections >200 to 300 mL can usually be seen on upright or decubitus chest radiographs. However, if the patient is supine, >1000 mL of blood may be missed due to posterior layering of blood, producing only diffuse haziness on that side (Figure 261-8). Point-of-care US may be used in the critically ill patient to detect hemothorax (Figure 261-9), showing a fluid density between visceral and parietal pleura normally occupied by lung tissue. CT has the highest sensitivity and specificity for detecting hemothorax.
Hemothorax. A. Anteroposterior view of the chest in patient with penetrating knife injury to the posterior left thorax. The site of injury is marked by a paperclip. Hazy opacity on the left, with associated volume loss in the left lung, is indicative of posteriorly layering hemothorax and atelectatic change. B. CT image in the same patient showing large hemothorax layering dependently in the supine patient. [Reproduced with permission from Block J, Jordanov MI, Stack LB, Thurman RJ (eds): The Atlas of Emergency Radiology. McGraw-Hill, Inc., 2013. Fig 4.23 & 4.24.]
Hemothorax. US can evaluate for pleural fluid, which usually represents hemothorax. Pleural fluid (hemothorax) can be seen superior to the diaphragm.
If the hemothorax is judged large enough to drain (>200 to 300 mL), tube thoracostomy remains the standard of care.
INDICATIONS FOR OPERATIVE INTERVENTION
Most patients with intrathoracic bleeding can be treated adequately by IV administration of fluids and evacuation of the hemothorax with a chest tube. Fewer than 5% of patients will require operative management. Consider surgical exploration in the following circumstances: >1500 mL of blood is evacuated immediately after tube thoracostomy, chest tube drainage of blood occurs at 150 to 200 mL/h for 2 to 4 hours, or persistent blood transfusion is required to maintain hemodynamic stability.
To establish the diagnosis of a pneumothorax with upright plain chest radiography, identify a thin white pleural line usually seen best in the upper lateral aspect of the affected hemithorax in the upright patient (Figure 261-10). Avoid interpreting skinfolds or a scapular border as a pneumothorax. If the radiograph is obtained with the patient supine, small pneumothoraces may not be apparent as air migrates to the anterior chest, resulting in loss of the interface between the parietal pleura and the air-filled pleural space. Point-of-care US can also diagnose simple pneumothorax. Sonographic imaging of a normal lung with the high-frequency linear probe at the anterior superior aspect of the chest will reveal "marching ants" or the "sliding lung sign," a result of the movement of the pleural layers during the ventilatory phase. This movement is absent in the presence of pneumothorax.
Pneumothorax. A. The pleural line is seen in the left hemithorax, but lateral to the pleura, there is increased lucency (air density) and an absence of lung markings. These findings should prompt concern for a pneumothorax. B. Enlarged area of the same image to further illustrate the increased lucency and absent lung markings lateral to the pleural line.
Pneumothorax is found in approximately 20% of patients with significant chest trauma.26 Traumatic pneumothorax can be open, closed, or occult. In an individual without preexisting cardiopulmonary disease, an isolated pneumothorax usually does not cause severe symptoms unless it occupies >40% of the hemithorax. Occult pneumothoraces may complicate the management of patients who are emergently taken to the operating room because intubation and positive-pressure ventilation may convert a small occult pneumothorax into a tension pneumothorax.
A pressure differential across the pulmonary pleura results in airflow down the gradient. Therefore, positive pulmonary pressure or negative intrapleural pressure during inspiration increases the tendency for air or blood to leak into the pleural cavity through any wound in the lung or chest wall. Any collection of air or blood within the pleural cavity may reduce vital capacity, increase intrathoracic pressure, and decrease minute ventilation and venous return to the heart. Additional air may be forced into the pleural cavity during expiration in patients with outflow obstruction, such as in chronic obstructive lung disease or airway occlusion, thus increasing the likelihood of tension pneumothorax.
Maintain a high suspicion for occult pneumothoraces in patients with more subtle injuries. Although chest radiography remains the most common diagnostic tool for detecting pneumothorax in the ED (Figure 261-11), it will miss between 17% and 80% of pneumothoraces for upright and supine chest radiographs, respectively. US is more sensitive than a supine radiograph and is rapid and accurate for detecting pneumothorax.10,11,13 Occult pneumothoraces are usually detected by CT (Figure 261-12).26 Importantly, with the exception of patients who may require intubation and positive-pressure ventilation (which may convert a small occult pneumothorax into a tension pneumothorax), the detection of occult pneumothoraces using chest CT has minimal clinical significance and does not improve outcome.7,8
Pneumothorax. This right-sided pneumothorax can be diagnosed by the absence of lung markings and increased (air density) lucency lateral to the pleural line.
Pneumothorax. Pneumothorax of the right hemithorax, with small bilateral posterior pulmonary contusions.
If pneumothorax is suspected despite normal initial chest radiography, repeat films or performing US or CT may be helpful. Pneumothorax after a stab wound may be delayed for up to 6 hours. Consequently, repeat chest imaging in 4 to 6 hours is indicated in these patients or at any time when symptoms worsen. Patients with initially asymptomatic stab wounds to the chest have a reported 12% incidence of delayed hemothorax or pneumothorax that required tube thoracostomy.27 A common practice is to observe patients with asymptomatic thoracic stab wounds, repeat the chest radiograph in 4 to 6 hours, and discharge the patient if no delayed pneumothorax is seen in the absence of other concerns.
If the patient cannot be observed closely, requires intubation and mechanical ventilation, or will be transported by air or over a long distance, insert a chest tube or small pleural catheter. Small pneumothoraces (<1.0 cm wide, confined to the upper third of the chest) that are unchanged on two chest radiographs taken 4 to 6 hours apart in an otherwise healthy individual can usually be treated by observation alone.
Occult pneumothoraces (small pneumothoraces not apparent on conventional chest imaging, but seen on a CT scan of the chest or abdomen) usually do not require chest tube drainage unless the patient requires mechanical ventilation. Avoid unnecessary tube thoracostomy because there is a 22% risk of major insertional, positional, and infective complications.28
In general, small- or moderate-sized pneumothoraces, once treated, do not cause significant problems unless there is a continuing air leak or preexisting cardiopulmonary disease. Even a small air leak usually will not result in serious complications, provided the lung is completely expanded. However, the incidences of empyema and bronchopleural fistula are greatly increased in pneumothoraces with continued air leak persisting for >24 to 48 hours.
If the lung does not completely expand or the pneumothorax does not evacuate, then investigate potential causes (Table 261-5).
TABLE 261-5Causes for Failure of Complete Lung Expansion or Evacuation of a Pneumothorax ||Download (.pdf) TABLE 261-5 Causes for Failure of Complete Lung Expansion or Evacuation of a Pneumothorax
Improper connections or leaks in the external tubing or water-seal collection apparatus
Improper positioning of the chest tube
Occlusion of bronchi or bronchioles by secretions or foreign body
Tear of one of the large bronchi
Large tear of the lung parenchyma
If a pneumothorax persists or there is a large air leak, perform emergency bronchoscopy to examine and clear the bronchi or to identify and repair any damage to the tracheobronchial tree. Continued large air leakage or failure of the lung to adequately expand, despite these measures, is an indication for early thoracotomy.
Subcutaneous emphysema in the neck or the presence of a crunching sound (Hamman's sign) over the heart during systole suggests the presence of a pneumomediastinum. This diagnosis can usually be made on chest radiography (Figure 261-13A) and is readily apparent on CT images of the chest (Figure 261-13B). Pneumomediastinum in blunt chest trauma is most commonly the result of alveolar rupture, followed by dissection along the bronchoalveolar sheath and subsequent spread of air to the mediastinum, a process known as the Macklin effect. Traumatic pneumomediastinum may be asymptomatic or can cause mild to moderate chest pain, voice change, cough, or stridor. Pneumomediastinum alone does not require further diagnostic testing or intervention unless the patient is symptomatic, in which case a search for other serious injuries to the larynx, trachea, major bronchi, pharynx, or esophagus is essential.
Pneumomediastinum. A. Blunt trauma to the chest while playing basketball. Patient had sudden onset of chest pain and shortness of breath. Subcutaneous emphysema was evident in the neck. Chest radiograph reveals mediastinal and subcutaneous air. B. In this same patient, a CT scan shows pneumomediastinum.
Pulmonary hematomas are parenchymal tears filled with blood. Although these generally resolve spontaneously over a few weeks, they sometimes can become infected and progress to lung abscesses. Infection is more likely in patients on a ventilator, who require prolonged chest tube drainage or who are post-thoracotomy.
PULMONARY LACERATION WITH HEMOPNEUMOTHORAX
Hemorrhage from pulmonary lacerations is most commonly seen in the setting of displaced rib fractures due to direct trauma from the exposed ends of bone. Hemorrhage may also be due to the effect of shear forces on preexisting pleural adhesions during rapid deceleration injuries or from penetrating chest injuries.