Lung, Trachea, and Esophagus
INTRODUCTION
Injuries to the chest are common after both blunt and penetrating trauma. Blunt thoracic injuries are responsible for approximately 8% of all trauma admissions in the United States, with motor vehicle crashes being the most common mechanism.1,2 In one recent report from the Los Angeles County Hospital, penetrating chest trauma accounted for 7% of all trauma admissions and 16% of all penetrating trauma admissions overall.3 A 1961 study described a 28% mortality with blunt chest injuries as compared to a 7% mortality following penetrating injury.4 Associated injures were common and were associated with a 42% mortality. These figures have not changed, as a more recent study described approximately a 25% fatality rate as a direct result of thoracic injury with chest trauma playing a contributing role in 50% of nonpenetrating injuries overall.5
Despite the prevalence of thoracic injury following trauma, the majority of patients can be managed nonoperatively. Between 18% and 40% of patients sustaining thoracic trauma can be treated with tube thoracostomy alone. A thoracotomy will be required for between 3% and 9% of patients. Even among those with penetrating trauma, only 14% of stab wounds and between 15% and 20% of gunshot wounds to the chest require thoracotomy.3
Operative mortality varies between 5% and 45%, with approximately 30% of patients requiring lung resection at the time of thoracotomy.4,5 This wide variability is almost certainly related to differences in mechanism of injury, inclusion of cardiac and major thoracic injury in some of the datasets, the extent of pulmonary resection needed, and concomitant extrathoracic injuries.4–13 The influence of thoracic trauma on mortality is particularly striking among patients who die within 1 hour of arriving to a trauma center. In those patients, thoracic trauma, especially thoracic vascular injury, is second only to central nervous system injury as the most common cause of death after hospital admission.
The determination of the optimal treatment for patients with thoracic injuries remains a challenge. Technological advances, particularly the evolution of sophisticated imaging, have allowed clinicians to make the diagnosis of major thoracic injury more quickly. Advances in critical care have made postoperative management more sophisticated. Improved approaches for nonoperative management may make the need for operative exploration even less frequent. Despite these advances, however, a modest number of patients still require thoracotomy. Thus, clinicians caring for injury must adequately appreciate the indications for operation and understand the treatment options in the emergency department as well as in the operating room. Thoughtful decision making based on a comprehensive appreciation of the anatomic relationships of the thoracic cavity and the physiologic principles that govern trauma is necessary to insure the highest survival and optimize functional recovery.
INJURY TO THE LUNGS
The lungs sit in each hemithorax. While physiologically quite complicated, in fact, the lungs are anatomically simple, consisting of primarily alveoli and blood vessels. The lungs have a dual blood supply, with a relatively large pulmonary artery and vein delivering significant volumes of blood at low pressure. While the bronchial vascular bed is characterized by a more substantial systemic pressure, the vessels of this vascular tree are quite small. The intercostal vessels in the chest wall also have systemic pressure, but possess larger-diameter vessels than their bronchial counterparts.
The bony thorax protects the lungs from injury. Thus, in adults, injury to the chest wall is a good marker for pulmonary injury following blunt trauma. The greater elasticity to the chest wall in children means that pulmonary injury can occur without evidence of injury to the chest wall.
The anatomic simplicity of the lungs means that a response to injury is relatively limited regardless of the severity and mechanism. The alveoli can rupture, causing a pneumothorax, or the lungs and parenchyma can bleed causing a hemothorax. The chest wall also bleeds when injured. Any of these can range from relatively trivial to life-threatening.
Very large pneumothoraces produce tension by shifting the mediastinal structures toward the contralateral side. In these situations, the anatomic distortion combined with the increase in intrathoracic pressure decreases cardiac output. If untreated, this can cause cardiac arrest. In contrast, large hemothoraces generally produce symptoms through the effects of hypovolemia. Very large hemothoraces, however, can also cause some degree of mediastinal anatomic distortion.
Injury to the lung can also cause intraparenchymal damage, usually pulmonary contusions or lacerations. These often cause symptoms such as shortness of breath or hypoxia. Following blunt trauma, these are often associated with rib fractures. Penetrating injury causes direct parenchymal damage. Radiographic findings often lag behind the clinical presentation. The increased use of CT scanning following most penetrating trauma allows the clinician to make the diagnosis earlier. As with many other entities, CT scanning may be overly sensitive and identify pulmonary pathology that is clinically unimportant.
Systemic air embolization, while rare, can also occur following direct pulmonary injury. This most often happens when patients are placed on positive pressure ventilation. If there is an injured bronchus adjacent to an injured blood vessel, air can be forced into the systemic circulation. This should be suspected when patients have sudden decompensation immediately after intubation.
Presentation and Evaluation
Any patient with blunt chest trauma or penetrating injury around the thoracic cavity is at risk for injury to the lung. The history may be provided by the patient, but often it is given by prehospital personnel. The mechanism of injury, time from injury, vital signs, and neurologic status at the scene and any changes during transport are critical components of an adequate history. With blunt injury specifics such as prolonged extrication, the location and degree of occupant compartment vehicle deformation may also provide useful information. With penetrating trauma, the specific details are usually vague and often unreliable.
Physical exam can often help make the diagnosis of intrathoracic injury. The presence of distended neck veins, tracheal deviation, subcutaneous emphysema, chest wall instability, absent breath sounds, or muffled heart sounds may all provide crucial information. Likewise, the absence of an upper extremity pulse suggests a proximal arterial injury. Vital signs should be frequently monitored with careful observation of the work of breathing and arterial saturation. Findings of subcutaneous air or decreased breath sounds should alert the clinician to the possibility of pneumothorax and/or hemothorax. Prompt placement of a tube thoracostomy in an unstable patient is wise, particularly as radiographic confirmation takes too long.
Penetrating thoracic trauma in a hemodynamically unstable patient warrants operative exploration. The decision regarding surgical exposure may be problematic especially if there is concomitant abdominal injury. The hemodynamically stable patient with penetrating thoracic injury may benefit from additional imaging, especially chest computed tomography which provides more detailed and organ-specific information as well as information about vascular anatomy.14–17
Following blunt trauma, stable patients require timely determination of the studies required to identify and characterize potential thoracic injuries. An arterial blood gas should be sent with the initial laboratory studies, and an electrocardiogram performed as indicated. A Focused Abdominal Sonography for Trauma (FAST) including the precordium should be performed. A portable chest radiograph (CXR) is routinely obtained, although some authors question the utility of this study in stable patients with a normal chest examination.16 We believe a CXR can rapidly yield critical information such as the identification of pleural space abnormalities including pneumothorax and hemothorax. If indicated, additional imaging studies such as thoracic ultrasound, a CT scan, esophagoscopy, bronchoscopy, and echocardiography should be obtained.
A CXR should make the diagnosis of any large hemothorax or pneumothorax. Since screening CXRs are usually performed supine, a hemothorax can be somewhat difficult to adequately diagnose. Haziness of one hemithorax when compared to the other may be the only real radiographic sign of blood in the pleural space. If this is of any substance, a chest tube should be placed. In addition, pure anterior or posterior pneumothoraces, even if they are large, may not be well seen on a CXR (Fig. 25-1). The CXR should be examined for a deep sulcus sign, displacement of the diaphragm inferiorly, which may be the only radiographic sign of a pneumothorax. A CXR will also allow the clinician to evaluate the mediastinum for the possibility of a traumatic aortic injury.
FIGURE 25-1 Sizeable anterior pneumothorax not visible on initial trauma chest x-ray. A substantial amount of air can be present either anterior or posterior to the lung and not be appreciated by initial plain film.
In the days of liberal CT scanning, particularly in patients with blunt trauma, many more patients are undergoing either CT scan of the chest or a total-body CT screening. This allows for more precise evaluation of the aorta and also gives a three-dimensional evaluation of the thorax.14,16,17 Pneumothoraces or hemothoraces not seen on chest x-ray are often seen on CT. If they are small and patients are asymptomatic, prudent practice is to simply observe these patients. Even if they require operations for an associated injury or intubation for positive pressure ventilation, the chances that these very small pneumothoraces will become clinically significant is relatively small. A follow-up CXR may be useful, particularly in patients with small pneumothoraces.
In general, patients found to have large pneumothoraces not seen on CXR are treated with tube thoracotomy, particularly in patients who are multiply injured. While it is possible that these can be treated without drainage, our belief has been that these patients may well become symptomatic and we prefer to treat these patients preemptively.
In general, hemothoraces are treated similarly to pneumothoraces. If they are small, observation is generally successful. However, any moderate-sized or large hemothorax should be drained with a tube thoracostomy. Blood left within the pleural cavity will clot and will not be able to be evacuated with a chest tube. The lung will become trapped and this will produce a fibrothorax. Small hemothoraces should be followed with serial exams and a repeat CXR as they occasionally slowly expand. Early recognition and triage is the best idea in these cases. When placed, tube thoracotomies are generally connected to a pleurevac and the pleurevac is connected to suction. Repeat chest x-rays should be obtained to demonstrate good tube placement and to evaluate the possibility of either retained blood or air.
Patients with significant lacerations to the lung will often have large air leaks or hemoptysis. Bronchoscopy can be helpful in such patients to evaluate the possibility of major airway injury, as well as to attempt to localize the injured lobe or segment; this can be especially important if there is significant injury to both hemithoraces. In these cases, bronchoscopy should be performed by a senior clinician. Blood within the airway must be suctioned clear to allow for good visualization of all of the lobar airway structures. Patients with large volumes of hemoptysis or significant air leaks who do not have major airway injury should be considered for thoracotomy and lung repair or lung resection.
If the patient is stable, CT scanning can also be quite helpful in patients with hemoptysis (Fig. 25-2). CT scanning should be able to demonstrate the anatomy of the lung injury and help localize the lobe or lobes most likely to be producing the air leak or hemoptysis. CT may also be able to demonstrate intraparenchymal vascular injuries. The pulmonary vascular tree is a low-pressure system and radiographic vascular injuries do not carry the same prognosis as do arterial vascular injuries identified within solid viscera in the abdomen. If symptomatic, operative exploration is generally the best idea. In a very selective group of patients who are a poor operative risk, transcatheter embolization offers an alternative to thoracotomy.
FIGURE 25-2 CXR and corresponding CT demonstrating right-sided pulmonary contusion. This patient had some minimal associate hemoptysis on presentation, which resolved.
The majority of patients with injury to the lung can be managed nonoperatively. Simple tube thoracostomy evacuates accumulated air and blood, and the lung should be reexpanded up against the chest wall. Peripheral lung injuries generally seal once the lung is reexpanded. As pressures in pulmonary circulation are relatively low, coapting the lung up against the chest wall generally stops bleeding as well.
A number of patients, however, will require thoracotomy for pulmonary and/or chest wall injury. Intercostal hemorrhage, particularly after penetrating trauma, usually continues even after evacuation of the associated hemothorax and/or pneumothorax. This may also be true for major chest wall injuries after blunt trauma where a number of intercostal vessels may be injured. Bleeding can be impressive from injured chest wall musculature as well. Major lung lacerations can produce symptoms by either a continued air leak or hemorrhage.
Indications for Operation
While indications for thoracotomy will be covered in a different chapter, some brief comments here may be helpful. Massive hemothorax, generally defined as 1,500 cm3 of blood in the chest cavity or persistent chest tube output of 200–250 cm3/h for 3 consecutive hours, is generally considered an indication for thoracotomy. In addition, a 24-hour chest tube output >1,500 cm3 is generally considered an indication for thoracic exploration. Hemodynamic instability that is thought to be referable to thoracic injury should virtually always prompt emergent thoracic exploration. As there is a linear relationship between total amount of thoracic hemorrhage and mortality, the surgeon should not delay thoracotomy when indicated.
Care must be exercised when measuring chest tube output. Chest tubes routinely become clotted and if poorly positioned, may not completely evacuate blood or air. Blood will then continue to accumulate within the thoracic cavity. A repeat CXR can be helpful in detecting a retained hemothorax. While a second chest tube may be helpful, patients with a large retained hemothorax should generally be explored and drained.
A number of patients may not need emergent thoracotomy, but may require thoracic operation at a later date. Examples of this include retained hemothorax, persistent air leak, missed injury, and pleural space infections. Many of these nonemergent procedures can be performed using a thorascopic technique.18,19 In general, air leak >7 days should be treated with an operation. Early evacuation of retained hemothorax prevents the clot from becoming fibrotic and trapping the lungs. Proven empyema is almost always best treated with operation.
Surgical Exposure
There are a number of ways to approach thoracic injury, each with advantages and disadvantages. It is imperative that the trauma surgeon be familiar with all of them. The clinical situation generally dictates which incision will be the best. Many patients have thoracotomy for a diagnosed condition such as a nonsealing air leak or a diagnosed tracheal or esophageal injury. In those cases, the incisions can be tailored to provide optimal exposure of the anatomic injury. However, many patients have true explorations for undiagnosed injuries such as in patients with a massive hemothorax or a large lung laceration that has not been localized. In those cases, the thoracic incision must be versatile and allow extension to provide greater exposure if that is necessary.
Hemodynamically unstable patients may not tolerate being put up in the lateral position, as it will exacerbate hypotension. In addition, patients with significant hemoptysis often do not tolerate being up in the lateral position. This puts them at risk for aspirating blood into the uninjured lung, which is now in the dependent position. In addition, there is sometimes the possibility of injury to an adjacent body cavity such as the abdomen and neck that requires operative care. This is especially true with penetrating thoracic trauma. The incision should be able to be modified in order to provide adequate exposure.
Commonly employed approaches are anterolateral, posterolateral, bilateral anterior thoracotomies (“clamshell”), and median sternotomy. The anterolateral approach is rapid and extending it across the midline affords excellent exposure to both pleural spaces and the anterior mediastinum. Likewise, the incision can be continued as a celiotomy for abdominal exploration, and is preferred over the posterolateral approach in the patient in shock. The main disadvantage of the anterolateral approach is the inability to provide optimal exposure of posterior thoracic structures. By extending the ipsilateral arm and placing a bump to elevate the thorax approximately 20°, the incision can be carried to the axilla improving posterior exposure (Fig. 25-3).
FIGURE 25-3 Anterolateral thoracotomy incision. Placing a bump to elevate the chest and extending the arm provides improved thoracic exposure.
The posterolateral thoracotomy affords optimal exposure of the hemithorax, especially the posterior structures, and is the standard incision for most elective thorax operations. Its lack of versatility limits the usefulness in trauma but is the preferred approach to repair intrathoracic tracheal and esophageal injuries. Median sternotomy provides excellent access to the heart, great vessels, and anterior mediastinum. It is versatile and can be extended as an abdominal, periclavicular, or neck incision (Fig. 25-4). Opening the pleura after sternotomy provides good access to either hemithorax. Depending on the surgeon’s experience, a lung resection can be performed. The “trapdoor” incision is rarely used since left-sided thoracic vessels can be approached via sternotomy with extension.20
FIGURE 25-4 Tracheal intubation on the operative field. Partial sternotomy was chosen to obtain control of the great vessels.
Operative Techniques
Regardless of the incision choice, patients who undergo emergency thoracic operations should first have a complete exploration. Once entering the chest, blood should be evacuated to allow the surgeons good visualization of the entire contents of the thoracic cavity. The lung should be mobilized by taking down the inferior pulmonary ligament. In patients with serious injury to the lung, temporary inflow occlusion can be obtained by compressing the hilum.
There are a number of techniques for hilar compression. Simple finger occlusion will temporarily occlude both the pulmonary artery and vein. A vascular clamp can be placed across the hilum if a longer period of occlusion is necessary. In addition, the lung can simply be twisted on itself at the level of the hilum. This occludes both the pulmonary artery and vein as well as the main stem bronchus. Patients with very tenuous hemodynamics may decompensate when the hilum is occluded. This is associated with a rapid rise in pulmonary artery pressure, which can cause acute right heart dysfunction or failure.
While a double-lumen endotracheal tube is often used in elective thoracic operations, it is virtually never used in trauma, especially for emergency thoracotomies. Use of a single-lumen endotracheal tube can make visualizing the organs within the thorax more difficult and perpetuates any air leak that may be coming from the injured lung. Holding ventilation while localizing an air leak and/or repairing or resecting the lung can be a useful technique. However, if the patient’s respiratory status is tenuous, any extended interruption of ventilation will precipitate decompensation. Manual compression of the adjacent lung may sufficiently consolidate the tissue to facilitate surgery on the lung.
There are a number of techniques for lung repair. Pneumonorrhaphy is the simplest technique and is generally used to treat superficial pulmonary lacerations. The laceration is simply closed with a running simple suture or mattress sutures. Between 20% and 30% of patients requiring emergency thoracic exploration will need a pulmonary resection. This can range from simple wedge resection to major anatomic resections. The widespread adoption of a variety of surgical staplers has increased the options for lung surgery following trauma. Peripheral lacerations not amenable to simple repair can be treated with a small wedge resection using any of the commercially available staplers. The lung parenchyma is generally retracted up to view using a lung clamp and the stapler is fired to excise the injured lung tissue.
More significant lung injuries, particularly those from gunshot wounds, are often best treated with tractotomy21–24 (Fig. 25-5). This is performed by placing the jaws of the stapler through the tract of the injury and firing it. This opens the lung and exposes the bleeding vessels and injured airways. These can then be individually ligated. Tissue thickness will determine whether tractotomy is appropriate and the appropriate-sized staples to use. At times, the staple line may need to be oversewn with a running suture. In general, relatively peripheral tracts are best treated with tractotomy, if more simple maneuvers are not appropriate. Long central missile tracts are usually not amenable to tracheotomy.
FIGURE 25-5 Pulmonary tractotomy with ligation of exposed hemorrhage sources. (Reproduced with permission from Petrone P, Asensio JA. Surgical management of penetrating pulmonary injuries. Scand J Trauma Resusc Emerg Med. 2009 23;17(1):8.)
Serious lobar injuries that are not amenable to tractotomy are often best treated with formal lobectomy. The lungs should be fully mobilized and the extent of injury absolutely determined before making a decision to do a lobectomy. The hilar blood vessels must be dissected free and the blood supply to the injured lobe identified. These can then be stapled or ligated, generally using heavy nonabsorbable ties. The bronchus is generally divided using a stapler and the injured lobe then removed.
Hilar injuries are a special problem and pose significant challenges. There are usually injuries to the major blood vessels as well as the proximal airways. Hemorrhagic shock is almost always present. In very proximal hilar injuries, inflow occlusion is virtually always necessary in order to gauge the extent of injury. Opening the pericardium and controlling the pulmonary artery and vein within the pericardium can be quite helpful in some patients.
Often, after good exposure, and delineation of injuries, many hilar injuries can be treated with either lobectomy or bilobectomy. However, certain injuries require pneumonectomy. Mortality after pneumonectomy for patients in shock approaches 100%.25 Patients die of either uncontrolled hemorrhage or acute right heart failure. It is imperative to make the decision to proceed with pneumonectomy as early as possible. If a number of attempts are made at lung salvage, and the patient is in profound shock, survival after pneumonectomy is rare.
The postoperative care after pneumonectomy is as important as early decision making. Virtually all short-term survivors develop right heart dysfunction and/or acute respiratory failure. Liberal use of transesophageal echocardiography can be very helpful in estimating volume status as well as function of both ventricles. Selective pulmonary artery vasodilation such as nitric oxide26 and sildenafil also improves cardiac function. Virtually all short-term survivors require inotropic support. Finally, use of sophisticated modes of ventilation support such as prone positioning and extracorporeal membrane oxygenation (ECMO) is often needed in the postoperative period.
As bronchial stump leak is a devastating complication following either lobectomy or pneumonectomy, we prefer to cover the bronchial stump with some live tissue. Rotating an intercostal muscle preserving the blood supply to cover the bronchial stump is attractive. Other options include mobilizing a tongue of pericardium. If a bronchial stump leak occurs later in the postoperative period, covering the stump leak with a local muscle flap such as latissimus dorsi or the omentum is another option.
The concept of damage control was originally described for abdominal trauma but is applicable in the chest as well. As in any damage control operation, control of hemorrhage is the primary concern. Thoracic packing to control nonmechanical bleeding can be quite helpful.27–30 It is important to be sure that the packs do not interfere with cardiac or pulmonary function. The chest is then temporarily closed and the patient is brought to the intensive care unit. We generally employ a suction dressing similar to what we use in the abdomen when doing thoracic damage control. When the patient is physiologically improved, the chest can be reexplored and closed. Very rarely, the chest cannot be closed at the time of the first operation and the chest retractor is left in place until the patient is more stable. Thoracic damage control has a 17% mortality, which is admirable, as nearly 70% of patients are acidotic, hypothermic, or coagulopathic.29,30
Video-Assisted Thoracoscopic Surgery
Increasing experience with thoracoscopy has contributed to enthusiasm for the use of video-assisted thoracoscopic surgery (VATS) techniques for a variety of sequela of trauma.18,19 As a diagnostic tool, VATS remains an acceptable alternative to laparoscopy in the identification of isolated diaphragmatic injuries particularly after penetrating trauma. It can also potentially be utilized to diagnose other minor injuries of the thoracic cavity not well visualized with traditional imaging, although these indications have not been well elucidated.
Therapeutically, there are several promising potential applications for VATS. While significant thoracic hemorrhage, pulmonary trauma, and other more severe injuries of the thoracic cavity and mediastinum remain matters best addressed with traditional open techniques, described indications for VATS include: surgical resection of persistent pleural air leak sources in the peripheral lung, ligation of isolated intercostal artery injury, rib fracture reduction, and evacuation of empyema or persistent retained hemothoraces.
The latter two indications remain among the most commonly described, with early operation proving to have the greatest success among published case series. Early VATS for retained hemothorax has proven to be the most successful utilization of the modality. There is, however, a relative paucity of literature on the topic, with the definition of “early” varying between described experiences. However, beyond 72 hours the degree of fibrotic change occurring within the thoracic cavity may preclude the safe conduct of VATS for the evacuation of blood or infectious collections. When treating retained hemothorax and/or empyema, the procedure consists of evacuation of fluid collections and clot followed by decortication of the parietal pleura as necessary. Air leaks are repaired or treated with small wedge resections.
VATS is performed in the operating room under general anesthesia. Double-lumen endotracheal intubation or other lung isolation techniques should be utilized to collapse the lung in the operative hemithorax to permit better utilization of the chest and its contents. The procedure is ideally done with the patient in the full lateral decubitus position with the affected side up. The field should be appropriately draped to facilitate conversion to an open posteriolateral thoracotomy if VATS is not sufficient.
The first port is placed along the fourth or fifth intercostal space in the midaxillary or anterior axillary line. The tip of the scapula serves as a nice landmark to facilitate appropriate positioning (Fig. 25-6). The lung is desufflated by anesthesia as the chest is entered and port placement completed. An angled thoracoscope is preferred for initial use, as it improves visualization of the pleural space recesses. An aspiration catheter can be placed coaxially to the optical port to facilitate the lavage and evacuation required for initial visualization. Additional ports can then be developed under direct visualization to address the pathology encountered.
FIGURE 25-6 Port placement for video-assisted thoracoscopic surgery (VATS) of the left hemithorax. The scapula and edge of the latissimus dorsi anteriorly are marked for reference.
The instruments used for VATS are the same as used for laparoscopic procedures. Conventional open surgery forceps can also be used. Cautery, however, should be utilized cautiously and in close coordination with anesthesia, as oxygen-rich air leaks and cautery may interact to create a fire hazard within the patient’s thorax. On completion the chest is irrigated with normal saline or sterile water. Thoracostomy tubes can then be placed and positioned under direct visualization, utilizing the developed port sites, and the lung reexpanded prior to wound closure. Following the procedure a chest x-ray should be obtained and the thoracostomy tubes can be managed using the same principles utilized following open thoracic surgery.
Outcomes
There is wide variably in reported mortality after thoracic injury. Blunt trauma results in mortality as high as 68%.1,2 This is probably related to higher ISS, lower GSC, and more associated nonthoracic injuries than those with penetrating injuries.4,6 There is also variation in the reported mortality with penetrating trauma. Cardiac and major vascular injuries and the percentage of major pulmonary resections all contribute to poorer outcomes.4,8 In a high-risk group of patients with penetrating injury requiring urgent lobectomy or pneumonectomy, the mortality was 38% and 66%, respectively, with pulmonary complications occurring in over half of the survivors.31
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