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Thoracic trauma

Scott M. Moore, Frederic M. Pieracci and Gregory J. Jurkovich

HISTORY

Almost all historical accounts of chest trauma are within the context of war and conflict. The oldest surgical treatise on record is the Edwin Smith Surgical Papyrus from around 3000 BC, which predates Hippocrates by approximately 1000 years and is believed to have been a handbook for the treatment of injuries sustained during military campaigns. However, few if any of these ancient writings effectively address intrathoracic injuries, as they mainly deal with extremity and soft-tissue wounds. Hemothorax and pneumothorax were first described about 200 years ago, and evacuation by either incisional drainage or tube placement was standard practice by the 1870s, with the development of underwater-seal drainage devices coming not long after. Ludwig Rehn described the first cardiorrhaphy for a penetrating injury in 1896. However, most of the major operations that will be described in this chapter have been innovations of the twentieth century, with guidelines for the management of penetrating thoracic trauma not established until World War II.

PRINCIPLES AND JUSTIFICATION

Trauma is the leading cause of death in individuals aged 1 to 44 years old, making it the number-one cause for productive life-years lost. Thoracic trauma is second only to head injury as a cause of death in the injured patient, with an overall mortality of 8.4% among those who present to the hospital. However, the burden of disease is likely to be much higher if one takes into account prehospital deaths and inhospital deaths in patients with multiple injuries, in which case thoracic trauma contributes to an estimated 50% of trauma-related deaths. Reflecting the importance of promptly addressing thoracic wounds, the systematic approach to the thoracic trauma patient is well described in all nine editions of Advanced Trauma Life Support. ¹ While less than 10% of blunt and only 10%-15% of penetrating chest injuries will require an operation, the lifesaving maneuvers of tube decompression, flail chest and open pneumothorax management, and airway control are essential skills for any surgeon. This chapter will describe procedures that are essential to the management of the thoracic trauma patient.

PREOPERATIVE ASSESSMENT AND PREPARATION

As with all trauma patients, the initial approach to the patient with a suspected chest injury involves a primary survey in which immediately life-threatening problems are identified and corrected as they are found. Assessment of the patient proceeds in the systematic “ABC” fashion—beginning with airway, followed by breathing, and ultimately circulation. British military surgeons faced with the devastating problem of improvised explosive devices and exsanguinating extremity injuries have advocated revising the ABC of trauma care to the “CABC” with the first emphasis being on catastrophic hemorrhage control, often with an extremity tourniquet. ² Injuries that must be addressed at this stage include upper airway injuries, open and tension pneumothorax, massive hemothorax, flail chest, and cardiac tamponade. Diagnosing these conditions may only require physical exam (e.g., tension pneumothorax), but many will require more detailed evaluations such as bedside ultrasound or even thoracotomy (e.g., cardiac tamponade) to diagnose and adequately treat.

Following completion of the primary survey, and with the use of adjuncts to the physical exam such as radiography and ultrasound, a more detailed secondary evaluation is done to search for potentially life-threatening problems such as simple pneumothorax, hemothorax, pulmonary contusion, tracheobronchial injuries, aerodigestive injury, blunt cardiac injury, aortic injury, and diaphragmatic injury.

One of the more challenging aspects at this stage involves choosing only the essential examination maneuvers, radiologic studies, and laboratory measurements that will direct the necessary actions to stabilize the patient, while omitting time-consuming tests that are both unlikely to change management acutely and may place patients at risk by subjecting them to long periods remote from resources. To this end, an understanding of the value of the various exam maneuvers, imaging modalities, and laboratory studies will help in expediting the initial work-up of the thoracic trauma patient, and minimize delay should an operation be necessary.

We briefly mention the tertiary survey at this point, to emphasize the need to review the physical exam, laboratory and radiographic findings, and adequacy of therapeutic plans for all documented injuries at an early stage in the hospital course, preferably within 24 hours of admission, to ensure no injuries were missed during the initial evaluation and recovery is proceeding as expected.

Key examination findings

Evaluations for airway patency and presence of breath sounds are essential components of the primary survey. In a hypotensive patient with unilateral absence of breath sounds, especially if accompanied by hyperresonance, a tension pneumothorax should be strongly suspected and a tube thoracostomy immediately performed. Alternatively, decreased unilateral breath sounds but without hyper-resonance may represent hemothorax. The appearance of distended neck veins can signify one of four potentially life-threatening conditions: (1) tension pneumothorax, (2) pericardial tamponade, (3) coronary air embolism, or (4) cardiac contusion with pump failure. Beck’s triad describes the classic exam findings of cardiac tamponade: muffled heart sounds, hypotension, and distended neck veins. Unfortunately, only 50% of patients with cardiac tamponade will demonstrate just one of these findings, and muffled heart sounds are often difficult to discern in the noisy trauma bay. Kussmaul’s sign (increased venous pressure with inspiration) and pulsus paradoxus (>10 mmHg decrease in systolic pressure with inspiration) are also characteristic of cardiac tamponade, but neither exam finding is sensitive. Exam findings of flail chest include paradoxical movement of the involved chest wall segment during therespiratory cycle. The detection of crepitance by simple palpation may help determine if a patient has rib fractures with underlying parenchymal lung injury. Lateral and anteroposterior compression of the chest wall is a useful maneuver for evaluating chest wall injuries, and the absence of pain in this setting essentially rules out clinically significant rib fractures. Distinguishing tension pneumothorax from cardiac tamponade in a trauma patient with hypotension is an essential skill of the trauma surgeon, since most inexperienced evaluators will jump to the conclusion that the hypotension is caused by blood loss.

Imaging studies

The application of ultrasound in the initial trauma evaluation (i.e., focused assessment sonography in trauma—FAST) can circumvent many of the difficulties associated with diagnosing cardiac tamponade by physical exam alone, having 97% sensitivity and 100% specificity for the presence of hemopericardium. ³ Currently, the supine portable chest X-ray is a vital portion of the secondary survey, allowing a rapid assessment for pneumothorax, hemothorax, rib fractures, great vessel injuries (widened mediastinum), and diaphragmatic rupture (presence of nasogastric tube in the chest). For penetrating injuries, using radiopaque labels to mark the wounds can greatly facilitate determining the missile tract, and plain X-rays are very useful for identifying retained bullets and bullet fragments. The extended focused assessment sonography in trauma, or eFAST, includes a sonographic evaluation for pneumothorax and has reported sensitivities of 98%, compared with 75% for the traditional supine chest X-ray, and has the potential to further increase the efficiency of the initial trauma evaluation. ³ As with all ultrasound studies, FAST and eFAST are significantly operator dependent, and there is an inadequate literature honestly addressing the false-negative rate of ultrasound in the emergency trauma setting. Formal echocardiography may be required in cases of questionable cardiac function (e.g., cardiac contusion, acute coronary syndrome); however, these evaluations are time-consuming and often unnecessary in the initial surgical decision-making.

The initial work-up for blunt thoracic aortic injuries begins with the chest radiograph, which has a reported sensitivity of 81%-100% and specificity of 60% for blunt aortic injury. ⁴ The characteristic findings of blunt-traumatic aortic injury include widening of the mediastinum to greater than 8 cm at the level of the aortic knob, obscuring of the aortic knob, depression of the left mainstem bronchus, displacement of the trachea at the T4 level, and presence of an apical pleural cap. Aortography was the preferred method for detecting aortic injuries until advances in computed tomographic angiography (CTA) technology and training caused a relative shift in this practice. Modern computed tomography (CT) equipment can obtain thin-slice (3-5 mm) cross-sectional imaging from the base of the skull to the pubic symphysis in less than 1 minute with a sensitivity and specificity that rivals aortography, making CTA the initial screening modality of choice at most centers for patients at high risk for aortic injuries. Furthermore, the images obtained by CTA can be reconstructed and used to plan endovascular interventions should an aortic injury be identified. While the location for blunt aortic injury is at the level of the ligamentum arteriosum in the vast majority of cases, injuries can occur at any site where the aorta is relatively fixed, and can also occur in regions adjacent to severe spinal column injuries. ⁵

Penetrating wounds that traverse the mediastinum or are in the vicinity of the heart or great vessels require a methodologic work-up. These injuries should be suspected on any patient with a penetrating wound within the area bounded by the sternal notch uperiorly, nipples laterally, and costal margin inferiorly (known traditionally as “the box”). FAST exam should be performed in the trauma bay to detect hemopericardium, with the caveat that false negatives can result when there is communication between the pericardial and pleural spaces. ⁶ Assuming patient stability, CTA provides excellent evaluations of the thoracic vasculature and also anatomic detail regarding the path of the offending object. Bullet fragments can occasionally cause significant signal artifact, and, in these circumstances, it is sometimes necessary to perform traditional aortography. If injury to the aerodigestive tract is suspected based on the CT results, then laryngo-tracheo-bronchoscopy and esophagography should be performed. Combining endoscopy with contrast studies of the esophagus has a near 100% sensitivity for detecting esophageal injuries.

ANESTHESIA

The patient that presents with hemodynamic collapse in the trauma bay does not require any anesthetic agents, though placement of an endotracheal tube should occur concurrently with resuscitative maneuvers, if not already done by prehospital personnel. For urgent operations done for major hemorrhage, the patient should be completely prepped and draped and the surgical team ready to make an incision prior to administration of anesthetic agents, due to the relatively high chance of cardiovascular collapse on anesthetic induction.

OPERATION

Bedside procedures for pneumothorax and hemothorax

Pneumothorax occurs when air enters the pleural space, usually as a result of parenchymal lung injury in the setting of rib fractures or penetrating trauma. In this setting, simple pneumothorax seen on plain chest X-ray should be treated by tube thoracostomy. Pneumothorax not seen on chest X-ray but seen on subsequent chest CT (known as “occult” pneumothorax) does not require thoracostomy in a hemodynamically normal patient without respiratory embarrassment. Rather, it can be safely followed on serial chest X-ray. Importantly, a simple pneumothorax can quickly convert to a life-threatening tension pneumothorax, especially in the setting of general anesthesia and positivepressure ventilation. Hemothorax is characterized as either simple (<1500 mL) or massive (>1500 mL), and if evident n plain chest X-ray should be treated by tube thoracostomy. The utility of draining smaller volumes of uncomplicated hemothorax that are only visible on chest CT remains controversial. The risk of introducing infection and pain must be weighed against the benefit of lung expansion and retained fluid evacuation. In our practice, we generally recommend evacuation of those hemothoraces estimated to be greater than 500 mL.

NEEDLE THORACOSTOMY

Decompression of a tension pneumothorax can be accomplished rapidly by placement of a large bore angiocatheter in the second intercostal space at the midclavicular line. However, in some patients with particularly thick chest walls, the length of commonly available angiocatheters (5 cm) may not be adequate to reach the pleural space. ⁷ Furthermore, the midclavicular line may not be the ideal location in such individuals; instead, the midaxillary line may provide a shorter distance for intrapleural insertion. ⁸ Tube thoracostomy is always required following successful needle thoracostomy, which invariably results in a simple pneumothorax regardless of whether one existed prior to its placement. Percutaneous approaches using the Seldinger technique (i.e., needle, wire, tube) and pigtail catheters have been advocated by some for pneumothorax without blood; however, such tubes are prone to kinking and can become clogged with even small quantities of blood within the pleural space. Due to these limitations, most busy trauma centers favor formal tube thoracostomy as the primary treatment modality for pneumoand hemothorax.

TUBE THORACOSTOMY

Preparation for tube thoracostomy should include skin disinfection with an alcohol-based 2% chlorhexidine solution, and the field should be widely draped, with the surgeon wearing sterile gloves, cap, gown, and face mask. The patient in extremis (e.g., tension pneumothorax) may require abbreviated skin preparation and draping. The value of antibiotics prior to chest tube insertion for preventing pneumonia or empyema is debated. This is exemplified by guidelines from the Eastern Association for the Surgery of Trauma, which initially recommended presumptive antibiotics when first released in 2002, while the updated guidelines in 2012 retracted this recommendation based on poor quality and conflicting data. ⁹ The optimal site is typically at the fifth intercostal space nipple level in males) just anterior to the midaxillary line.Local anesthetic should be liberally infiltrated into the skin subcutaneous tissues, intercostal muscles, and pleura. A 2-3 cm horizontal incision is made and a Kelly clamp is used to dissect through the tissues in the direction of the intended interspace, taking care to dissect just over the top of the lower rib. Once the pleura is reached, it should be bluntly punctured forcefully, ideally with a finger, but in a controlled fashion so as to avoid injury to underlying lung. Generous spreading of the tract with the Kelly clamp at this point will greatly facilitate tube placement. A gloved finger should then be inserted into the pleural space. This maneuver may provide several pieces of useful information including confirmation of intrapleural placement, diagnosis of cardiac tamponade (left side), diagnosis of diaphragmatic rupture, and sweeping away of any adhesions. The chest tube is then clamped at its tip and directed through the tract and into the pleural space. As trauma patients often have a combination of both fluid and air in the pleural space (i.e., hemopneumothorax), the tube should be directed along the posterior chest wall toward the apex. Spinning the tube during advancement helps prevent lodgment into the fissure, and fogging of the tube confirms intrapleural placement. The tube is then secured with heavy suture, attached to a water-seal drainage device, and covered with an occlusive and sterile dressing. Authorities have historically recommended large bore chest tubes (36-40 Fr) for treatment of hemothorax, though no studies have supported this assertion, and studies have shown no difference between small (28-32 Fr) and large (36-40 Fr) tubes for successful evacuation of hemothorax. ¹⁰ The need for emergent operative exploration is based on both initial output (>1000 mL for penetrating and >1500 mL for blunt) and subsequent output (>300 mL per hour for 2 consecutive hours for both blunt and penetrating). Finally, emergent operative exploration is indicated for lower outputs in the setting of hemodynamic instability.

Temporizing measures for cardiac tamponade

Adjunctive procedures such as pericardiocentesis and subxiphoid pericardiotomy (see “Subxiphoid pericardiotomy” subsection) were historically used mostly for the diagnosis of hemopericardium, although these procedures have been supplanted in this role by pericardial ultrasound due to the latter’s high sensitivity and noninvasiveness. Effective treatment for cardiac tamponade mandates immediate ecompression and repair of the underlying cardiac injury, which requires either a sternotomy or thoracotomy incision. Though transfer to the operating room is preferred, some patients will require immediate intervention in the trauma bay (i.e., emergency department thoracotomy [EDT]—see “ED thoracotomy” subsection). The role of pericardiocentesis as a therapeutic procedure is less clear, but most centers have abandoned therapeutic pericardiocentesis due to concerns over delays in definitive operative intervention. Occasionally, experienced surgical personnel are not immediately available or ultrasound results are equivocal, and decompression of cardiac tamponade by pericardiocentesis is necessary. Furthermore, a single-center experience recently reported that performance of pericardiocentesis in the emergency department (ED) does not delay definitive therapy and that early relief of cardiac tamponade leads to improvements in patient hemodynamics. ¹¹

PERICARDIOCENTESIS

This procedure is performed using sterile technique and a long (at least 15 cm) 16to 18-gauge angiocatheter, with continuous electrocardiographic monitoring throughout the procedure. The skin is entered at a 45-degree angle and 1-2 cm inferior and to the left side of the xiphocondral junction. The needle is advanced slowly in the direction of the left shoulder until blood is withdrawn, signifying entry into the pericardial sac. As much blood should be removed as possible, and then a catheter attached to a three-way stopcock left in place. The Seldinger technique may be used for placement of the pericardial catheter, or it may be inserted directly over the needle. Inadvertent injury to the myocardium during needle advancement or during aspiration will be detected by ST-T wave changes on the electrocardiogram monitor, which should prompt immediate withdrawal of the needle. The utility of pericardiocentesis for both diagnostic and therapeutic purposes can be limited by the difficulty in aspirating clotted blood within the pericardial sac. Furthermore, although temporary relief of symptoms may occur, all trauma patients with acute cardiac tamponade ultimately require complete examination of the heart and cardiorrhaphy of any injuries.

OPERATION

Major procedures for thoracic trauma

POSITIONING

The choice of incision influences positioning; however, unstable patients should remain in the supine position, as lateral positioning limits access to the superior mediastinum and opposite hemithorax, compromises ventilation of the dependent lung, results in pooling of blood within the contralateral bronchial tree, and limits exploration of other body cavities. For stable patients undergoing planned thoracotomy, lateral positioning facilitates posterolateral exposure, but flexion of the bed should only be performed if spinal injury has been excluded. All patients undergoing exploratory surgery following trauma should be prepped fromthe neck to the knees to permit full access to incidentally discovered injuries and, if needed, exposure for saphenous vein harvesting.

INCISIONS

Injury mechanism, patient stability, anticipated intrathoracic pathology, and associated nonthoracic injuries will dictate the most appropriate incision:

• Left anterolateral thoracotomy provides the most options for immediate resuscitative maneuvers in the pulseless trauma patient, regardless of the underlying pathology, and is especially useful for penetrating cardiac wounds leading to cardiovascular collapse. With the exception of diagnosis of cardiac tamponade, this is the “workhouse” incision for the unstable trauma patient with suspected intrathoracic trauma. This incision is easily extended to a transsternal bilateral anterolateral (aka “clamshell”) thoracotomy if needed, as described next.
  
• Transsternal bilateral anterolateral thoracotomy (i.e., “clamshell thoracotomy”) is useful in the salvaged patient undergoing EDT, as it allows the surgeon to address right thoracic injuries and improves overall exposure to the left chest and mediastinum. The sternum is transected with a Lebsche knife followed by suture ligation of the internalmammary arteries and veins, and the incision is carried through the fifth intercostal space on the right side. The main limitation of the clamshell thoracotomy is the limited exposure of the aortic arch vessels. This exposure can be improved by a superior ternotomy extension.
  
• Median sternotomy is versatile for addressing thoracic trauma due to its excellent exposure of the right heart, ascending aorta and arch, and arch vessels, and the relative ease of opening and closing. It may also be extended into the neck or supraclavicular fossa or exposure of the innominate artery, and proximal subclavian and common carotid arteries. However, exposure of posterior mediastinal structures is very limited, and cross-clamping of the descending thoracic aorta is not possible.
  
• Right posterolateral thoracotomy provides the best exposure of the right lung, trachea, carina, right and proximal left mainstem bronchi, and proximal and middle esophagus. The right heart is also easily accessible, though the left lung, distal left airways, descending thoracic aorta, aortic arch, arch vessels, and left heart are not accessible through this incision.
  
• Left posterolateral thoracotomy provides ideal exposure of the left lung and hilum, descending thoracic aorta, distal esophagus, and distal left mainstem bronchus. As mentioned, left thoracotomy does not afford access to the right chest, and the posterolateral incision further limits exposure to the right heart, though the left heart chambers are accessible.
  
• Left trapdoor thoracotomy combines a left anterolateral thoracotomy incision and partial sternotomy with left supraclavicular extension. Though controversial due to its associated morbidity, this incision can prove useful in the specific circumstance where a resuscitative thoracotomy has been performed and an injury is encountered in the proximal left subclavian artery. The sternocleidomastoid and strap muscles are transected during the supraclavicular extension to provide full exposure, and care must be taken to avoid injury to the left phrenic nerve that runs along the surface of the anterior scalene muscle.

ED (RESUSCITATIVE) THORACOTOMY

The development of well-organized prehospital trauma systems has led to increased survival among individuals sustaining major penetrating and blunt injuries. This has increased the proportion of trauma patients suffering a witnessed cardiac arrest during their ED evaluation or minutes prior to their arrival. EDT is a resuscitative maneuver with the goal of stabilizing the patient for transport to the operating room, where either definitive repair or damage control of thoracic injuries can be accomplished. The goals of EDT vary based on the mechanism of injury and can include a combination of the following: release of cardiac tamponade; control of hemorrhage from cardiac wounds; internal cardiac compression; cross-clamping of the pulmonary hilum in the setting of major lung hemorrhage, air embolism, or massive bronchopleural fistula; and cross-clamping of the descending thoracic aorta to maximize coronary and cerebral perfusion and limit hemorrhage from the lower torso and extremities. The best outcomes occur in those sustaining penetrating stab wounds to the heart where cardiac tamponade is the principle cause of cardiovascular collapse, whereas the most dismal outcomes occur in blunt-trauma patients whose pulses were lost prior to arrival to the ED. Though indications for EDT vary between trauma centers, most would agree that EDT should not be performed if prehospital personnel were required to perform cardiopulmonary resuscitation for more than 10 minutes for blunt trauma, and for more than 15 minutes for penetrating mechanisms. The essential instruments for EDT include a No. 10-blade scalpel, Finochietto retractor, toothed forceps, Mayo scissors, Satinsky (or DeBakey) vascular clamps (at least two), long needle holder and 2-0 polypropylene sutures, and a Lebsche knife and mallet. Other materials that may be needed include silk ties, Teflon pledgets, and a skin stapler

1. EDT is performed through a left anterolateral thoracotomy through the fifth intercostal space, which is just below the nipple in males and in the inframammary crease in females. The incision should start just to the right side of the sternum and be carried horizontally across the left chest until just beyond the nipple, at which point the incision is angled gently toward the left axilla. (See Figure 3.1.)
   
2. Once the intercostal muscles are reached, either the scalpel or scissors can be used to complete the incision (see Figure 3.2).
   
3. If a penetrating cardiac wound is suspected, attention should be immediately directed toward release of cardiac tamponade and repair of cardiac wounds. A low threshold for extension to a bilateral anterior thoracotomy should be maintained if a cardiac wound is suspected. This will allow for maximal exposure of the injured area. The pericardium can be quite tense and may require a scalpel to incise. The pericardiotomy is then extended vertically in a direction parallel and anterior to the phrenic nerve. (See Figure 3.3.)
   
4. Complete delivery of the heart from the pericardial sac not only allows for more thorough examination and control of cardiac injuries but also facilitates open cardiac massage in the setting of cardiac arrest. Intracardiac injection of epinephrine (1 mg) may also be employed, as well as cardiac defibrillation (20-50 J) using internal paddles positioned on the anterior and posterior aspects of the heart. Finally, intraatrial infusion of blood products may be achieved via cannulation of either atrial appendage around a pursestring stitch and using a Foley catheter. (See Figure 3.4.)

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