Blunt Chest Trauma Seflucr. Dr. Cristina Grigorescu Clinic of Thoracic Surgery
Chest trauma is a significant source of morbidity and mortality in the United States. • Blunt injury to the chest can affect any one or all components of the chest wall and thoracic cavity. These components include the bony skeleton (ribs, clavicles, scapulae, sternum), lungs and pleurae, tracheobronchial tree, esophagus, heart, great vessels of the chest, and the diaphragm.
Records describing chest trauma and its treatment date to antiquity. An ancient Egyptian treatise (the Edwin Smith Surgical Papyrus [circa 3000-1600 BC]) and Hippocrates' writings in the 5th century contain a series of trauma case reports, including thoracic injuries
Morbidity and mortality • Trauma is the leading cause of death, morbidity, hospitalization, and disability in Americans aged 1 year to the middle of the fifth decade of life. As such, it constitutes a major health care problem. According to the Centers for Disease Control and Prevention, approximately 118,000 accidental deaths occurred in the United States in 2005.
Frequency • Trauma is responsible for more than 100,000 deaths annually in the United States.1 Estimates of thoracic trauma frequency indicate that injuries occur in 12 persons per million population per day. Approximately 33% of these injuries require hospital admission. Overall, blunt thoracic injuries are directly responsible for 20-25% of all deaths, and chest trauma is a major contributor in another 50% of deaths.
Etiology • By far, the most important cause of significant blunt chest trauma is motor vehicle accidents (MVAs). MVAs account for 70-80% of such injuries. As a result, preventive strategies to reduce MVAs have been instituted in the form of speed limit restriction and the use of restraints. Pedestrians struck by vehicles, falls, and acts of violence are other causative mechanisms. Blast injuries can also result in significant blunt thoracic trauma.
Pathophisiology • The major pathophysiologies encountered in blunt chest trauma involve derangements in the flow of air, blood, or both in combination. Sepsis due to leakage of alimentary tract contents, as in esophageal perforations, also must be considered. • Blunt trauma commonly results in chest wall injuries (eg, rib fractures). The pain associated with these injuries can make breathing difficult, and this may compromise ventilation
Direct lung injuries, such as pulmonary contusions (see the image below), are frequently associated with major chest trauma and may impair ventilation by a similar mechanism. • Shunting and dead space ventilation produced by these injuries can also impair oxygenation.
Space-occupying lesions, such as pneumothoraces, hemothoraces, and hemopneumothoraces, interfere with oxygenation and ventilation by compressing otherwise healthy lung parenchyma. A situation of special concern is tension pneumothorax in which pressure continues to build in the affected hemithorax as air leaks from the pulmonary parenchyma into the pleural space. This can push mediastinal contents toward the opposite hemithorax. Distortion of the superior vena cava by this mediastinal shift can result in decreased blood return to the heart, circulatory compromise, and shock.
At the molecular level, animal experimentation supports a mediator-driven inflammatory process further leading to respiratory insult after chest trauma. Following blunt chest trauma, several blood-borne mediators are released, including interleukin-6, tumor necrosis factor, and prostanoids. These mediators are thought to induce secondary cardiopulmonary changes. Blunt trauma that causes significant cardiac injuries (eg, chamber rupture) or severe great vessel injuries (eg, thoracic aortic disruption) frequently results in death before adequate treatment can be instituted. This is due to immediate and devastating exsanguination or loss of cardiac pump function. This causes hypovolemic or cardiogenic shock and death.
Clinical • The clinical presentation of patients with blunt chest trauma varies widely and ranges from minor reports of pain to florid shock. The presentation depends on the mechanism of injury and the organ systems injured. • Obtaining as detailed a clinical history as possible is extremely important in the assessment of a patient with a blunt thoracic trauma. The time of injury, mechanism of injury, estimates of MVA velocity and deceleration, and evidence of associated injury to other systems (eg, loss of consciousness) are all salient features of an adequate clinical history. Information should be obtained directly from the patient whenever possible and from other witnesses to the accident if available.
For the purposes of this discussion, the authors divide blunt thoracic injuries into 3 broad categories as follows: (1) chest wall fractures, dislocations, and barotrauma (including diaphragmatic injuries); (2) blunt injuries of the pleurae, lungs, and aerodigestive tracts; and (3) blunt injuries of the heart, great arteries, veins, and lymphatics. A concise exegesis of the clinical features of each condition in these categories is presented. This classification is used in subsequent sections to outline indications for medical and surgical therapy for each condition.
Relevant Anatomy • The thorax is bordered superiorly by the thoracic inlet, just cephalad to the clavicles. The major arterial blood supply to and venous drainage from the head and neck pass through the thoracic inlet. • The thoracic outlets form the superolateral borders of the thorax and transmit branches of the thoracic great vessels that supply blood to the upper extremities. The nerves that comprise the brachial plexus also access the upper extremities via the thoracic outlet. The veins that drain the arm, most importantly the axillary vein, empty into the subclavian vein, which returns to the chest via the thoracic outlet.
Inferiorly, the pleural cavities are separated from the peritoneal cavity by the hemidiaphragms. Communication routes between the thorax and abdomen are supplied by the diaphragmatic hiatuses, which allow egress of the aorta, esophagus, and vagal nerves into the abdomen and ingress of the vena cava and thoracic duct into the chest. • The chest wall is composed of layers of muscle, bony ribs, costal cartilages, sternum, clavicles, and scapulae. In addition, important neurovascular bundles course along each rib, containing an intercostal nerve, artery, and vein. The inner lining of the chest wall is the parietal pleura. The visceral pleura invests the lungs. Between the visceral and parietal pleurae is a potential space, which, under normal conditions, contains a small amount of fluid that serves mainly as a lubricant.
The lungs occupy most of the volume of each hemithorax. Each is divided into lobes. The right lung has 3 lobes, and the left lung has 2 lobes. Each lobe is further divided into segments. • The trachea enters through the thoracic inlet and descends to the carina at thoracic vertebral level 4, where it divides into the right and left mainstem bronchi. Each mainstem bronchus divides into lobar bronchi. The bronchi continue to arborize to supply the pulmonary segments and subsegments
The heart is a mediastinal structure contained within the pericardium. The right atrium receives blood from the superior vena cava and inferior vena cava. Right atrial blood passes through the tricuspid valve into the right ventricle. Right ventricular contraction forces blood through the pulmonary valve and into the pulmonary arteries. Blood circulates through the lungs, where it acquires oxygen and releases carbon dioxide. Oxygenated blood courses through the pulmonary veins to the left atrium. The left heart receives small amounts of nonoxygenated blood via the thebesian veins, which drain the heart, and the bronchial veins. Left atrial blood proceeds through the mitral valve into the left ventricle.
Left ventricular contraction propels blood through the aortic valve into the coronary circulation and the thoracic aorta, which exits the chest through the diaphragmatic hiatus into the abdomen. A ligamentous attachment (remnant of ductusarteriosus) exists between the descending thoracic aorta and pulmonary artery just beyond the take-off of the left subclavian artery.
The esophagus exits the neck to enter the posterior mediastinum. Through much of its course, it lies posterior to the trachea. In the upper thorax, it lies slightly to the right with the aortic arch and descending thoracic aorta to its left. Inferiorly, the esophagus turns leftward and enters the abdomen through the esophageal diaphragmatic hiatus. The thoracic duct arises primarily from the cisternachyli in the abdomen. It traverses the diaphragm and runs cephalad through the posterior mediastinum in proximity to the spinal column. It enters the neck and veers to the left to empty into the left subclavian vein.
Approach Considerations • Initial emergency workup of a patient with multiple injuries should begin with the ABCs of trauma, with appropriate intervention taken for each step.
Laboratory studies • CBC count • A CBC count is a routine laboratory test for most trauma patients. The CBC count helps gauge blood loss, although the accuracy of findings to help determine acute blood loss is not entirely reliable. Other important information provided includes platelet and white blood cell counts, with or without differential
Arterial blood gas • Arterial blood gas (ABG) analysis, though not as important in the initial assessment of trauma victims, is important in their subsequent management. ABG determinations are an objective measure of ventilation, oxygenation, and acid-base status, and their results help guide therapeutic decisions such as the need for endotracheal intubation and subsequent extubation.
Serum chemistry profile • Patients who are seriously injured and require fluid resuscitation should have periodic monitoring of their electrolyte status. This can help to avoid problems such as hyponatremia or hypernatremia. The etiology of certain acid-base abnormalities can also be identified, eg, a chloride-responsive metabolic alkalosis or hyperchloremic metabolic acidosis.
Coagulation profile • The coagulation profile, including prothrombin time/activated partial thromboplastin time, fibrinogen, fibrin degradation product, and D-dimer analyses, can be helpful in the management of patients who receive massive transfusions (eg, >10 U packed RBCs). Patients who manifest hemorrhage that cannot be explained by surgical causes should also have their profile monitored.
Serum troponin levels • The rate of cardiac injury in patients with blunt chest trauma varies widely depending upon the diagnostic criteria. Troponin is a protein specific to cardiac cells. While elevated serum troponin I levels correlate with the presence of echocardiographic or electrocardiographic abnormalities in patients with significant blunt cardiac injuries, these levels have low sensitivity and predictive values in diagnosing myocardial contusion in those without. As such, troponin I level determination does not, by itself, help predict the occurrence of complications that may require admission to the hospital. Accordingly, their routine use in this clinical situation is not well supported.
Serum myocardial muscle creatinekinaseisoenzyme levels • Measurement of serum myocardial muscle creatinekinaseisoenzyme (creatinekinase-MB) levels is frequently performed in patients with possible blunt myocardial injuries. The test is rapid and inexpensive. This diagnostic modality has recently been criticized because of poor sensitivity, specificity, and positive predictive value in relation to clinically significant blunt myocardial injuries.
Serum lactate levels • Lactate is an end product of anaerobic glycolysis and, as such, can be used as a measure of tissue perfusion. Well-perfused tissues mainly use aerobic glycolytic pathways. Persistently elevated lactate levels have been associated with poorer outcomes. Patients whose initial lactate levels are high but are rapidly cleared to normal have been resuscitated well and have better outcomes.
Blood type and crossmatch • Type and crossmatch are some of the most important blood tests in the evaluation and management of a seriously injured trauma patient, especially one who is predicted to require major operative intervention.
Chest radiographs • The chest radiograph (CXR) is the initial radiographic study of choice in patients with thoracic blunt trauma. A chest radiograph is an important adjunct in the diagnosis of many conditions, including chest wall fractures, pneumothorax, hemothorax, and injuries to the heart and great vessels (eg, enlarged cardiac silhouette, widened mediastinum). • In contrast, certain cases arise in which physicians should not wait for a chest radiograph to confirm clinical suspicion. The classic example is a patient presenting with decreased breath sounds, hyperresonanthemithorax, and signs of hemodynamic compromise (ie, tension pneumothorax). This should be immediately decompressed before obtaining a chest radiograph.
Chest CT scan • Due to lack of sensitivity of chest radiography to identify significant injuries, computed tomography (CT) scan of the chest is frequently performed in the trauma bay in the hemodynamically stable patient. In one study, 50% of patients with normal chest radiographs were found to have multiple injuries on chest CT scan. As a result, obtaining a chest CT scan in a supposedly stable patient with significant mechanism of injury is becoming routine practice. • .
Helical CT scanning and CT angiography (CTA) are being used more commonly in the diagnosis of patients with possible blunt aortic injuries. Most authors advocate that positive findings or findings suggestive of an aortic injury (eg, mediastinal hematoma) be augmented by aortography to more precisely define the location and extent of the injury.
Aortogram • Aortography has been the criterion standard for diagnosing traumatic thoracic aortic injuries. However, its limited availability and the logistics of moving a relatively critical patient to a remote location make it less desirable. In addition, with the new generation spiral CT scanners, which have 100% sensitivity and greater than 99% specificity, the role of aortography in the evaluation of trauma patients is declining. However, where spiral CT is equivocal, aortography can provide a more exact delineation of the location and extent of aortic injuries. Aortography is much better at demonstrating injuries of the ascending aorta. In addition, it is superior at imaging injuries of the thoracic great vessels
Thoracic ultrasound • Ultrasound examinations of the pericardium, heart, and thoracic cavities can be expeditiously performed by surgeons and emergency department (ED) physicians within the ED. Pericardial effusions or tamponade can be reliably recognized, as can hemothoraces associated with trauma. The sensitivity, specificity, and overall accuracy of ultrasound in these settings are all more than 90%
Contrast esophagogram • Contrast esophagograms are indicated for patients with possible esophageal injuries in whom esophagoscopy results are negative. The esophagogram is first performed with water-soluble contrast media. If this provides a negative result, a barium esophagogram is completed. If these results are also negative, esophageal injury is reliably excluded. • Esophagoscopy and esophagography are each approximately 80-90% sensitive for esophageal injuries. These studies are complementary and, when performed in sequence, identify nearly 100% of esophageal injuries
Focused Assessment for the Sonographic Examination of the Trauma Patient • The Focused Assessment for the Sonographic Examination of the Trauma Patient (FAST) is routinely conducted in many trauma centers. Although mainly dealing with abdominal trauma, the first step in the examination is to obtain an image of the heart and pericardium to assess for evidence of intrapericardial bleeding
Twelve-lead electrocardiogram • The 12-lead electrocardiogram (ECG) is a standard test performed on all thoracic trauma victims. ECG findings can help identify new cardiac abnormalities and help discover underlying problems that may impact treatment decisions. Furthermore, it is the most important discriminator to help identify patients with clinically significant blunt cardiac injuries. • Patients with possible blunt cardiac injuries and normal ECG findings require no further treatment or investigation for this injury. The most common ECG abnormalities found in patients with blunt cardiac injuries are tachyarrhythmias and conduction disturbances, such as first-degree heart block and bundle-branch blocks.
Transesophageal echocardiography • Transesophageal echocardiography (TEE) has been extensively studied for use in the workup of possible blunt rupture of the thoracic aorta. Its sensitivity, specificity, and accuracy in the diagnosis of this injury are each approximately 93-96%. Its advantages include the easy portability, no requisite contrast, minimal invasiveness, and short time required to perform. TEE can also be used intraoperatively to help identify cardiac abnormalities and monitor cardiac function. • The disadvantages include operator expertise, long learning curve, and the fact that it is relatively weak at helping identify injuries of the descending aorta.
Transthoracic echocardiography • Transthoracic echocardiography (TTE) can help identify pericardial effusions and tamponade, valvular abnormalities, and disturbances in cardiac wall motion. TTEs are also performed in cases of patients with possible blunt myocardial injuries and abnormal ECG findings.
Flexible or rigid esophagoscopy • Esophagoscopy is the initial diagnostic procedure of choice in patients with possible esophageal injuries. Either flexible or rigid esophagoscopy is appropriate, and the choice depends on the experience of the clinician. Some authors prefer rigid esophagoscopy to evaluate the cervical esophagus and flexible esophagoscopy for possible injuries of the thoracic and abdominal esophagus. If esophagoscopy findings are negative, esophagography should be performed as outlined above
Fiberoptic or rigid bronchoscopy • Fiberoptic or rigid bronchoscopy is performed in patients with possible tracheobronchial injuries. Both techniques are extremely sensitive for the diagnosis of these injuries. Fiberopticbronchoscopy offers the advantage of allowing an endotracheal tube to be loaded onto the scope and the endotracheal intubation to be performed under direct visualization if necessary.
Indications and Contraindications • Indications • Operative intervention is rarely necessary in blunt thoracic injuries. In one report, only 8% of cases with blunt thoracic injuries required an operation. Most can be treated with supportive measures and simple interventional procedures such as tube thoracostomy.
The following section reviews indications for surgical intervention in blunt traumatic injuries according to the previously presented classification system. Surgical indications are further stratified into conditions requiring an immediate operation and those in which surgery is needed for delayed manifestations or complications of trauma
Chest wall fractures, dislocations, and barotrauma (including diaphragmatic injuries) • Indications for immediate surgery include (1) traumatic disruption with loss of chest wall integrity and (2) blunt diaphragmatic injuries. • Relatively immediate and long-term indications for surgery include (1) delayed recognition of blunt diaphragmatic injury and (2) the development of a traumatic diaphragmatic hernia
Blunt injuries of the pleurae, lungs, and aerodigestive tracts • Indications for immediate surgery include (1) a massive air leak following chest tube insertion; (2) a massive hemothorax or continued high rate of blood loss via the chest tube (ie, 1500 mL of blood upon chest tube insertion or continued loss of 250 mL/h for 3 consecutive hours); (3) radiographically or endoscopically confirmed tracheal, major bronchial, or esophageal injury; and (3) the recovery of gastrointestinal tract contents via the chest tube.
Relatively immediate and long-term indications for surgery include (1) a chronic clotted hemothorax or fibrothorax, especially when associated with a trapped or nonexpanding lung; (2) empyema; (3) traumatic lung abscess; (4) delayed recognition of tracheobronchial or esophageal injury; (5) tracheoesophageal fistula; and (6) a persistent thoracic duct fistula/chylothorax.
Blunt injuries of the heart, great arteries, veins, and lymphatics • Indications for immediate surgery include (1) cardiac tamponade, (2) radiographic confirmation of a great vessel injury, and (3) an embolism into the pulmonary artery or heart. • Relatively immediate and long-term indications for surgery include the late recognition of a great vessel injury (eg, development of traumatic pseudoaneurysm).
Contraindications • No distinct, absolute contraindications exist for surgery in blunt thoracic trauma. Rather, guidelines have been instituted to define which patients have clear indications for surgery (eg, massive hemothorax, continued high rates of blood loss via chest tube). • A controversial area has been the use of ED thoracotomy in patients with blunt trauma presenting without vital signs. The results of this approach in this particular patient population have been dismal and have led many authors to condemn it.
Rib fractures Rib fractures are the most common blunt thoracic injuries. Ribs 4-10 are most frequently involved. Patients usually report inspiratory chest pain and discomfort over the fractured rib or ribs. Physical findings include local tenderness and crepitus over the site of the fracture. If a pneumothorax is present, breath sounds may be decreased and resonance to percussion may be increased. Rib fractures may also be a marker for other associated significant injury, both intrathoracic and extrathoracic. In one report, 50% of patients with blunt cardiac injury have rib fractures. Fractures of ribs 8-12 should raise the suggestion of associated abdominal injuries. Lee and colleagues reported a 1.4- and 1.7-fold increase in the incidence of splenic and hepatic injury, respectively, in those with rib fractures
Elderly patients with 3 or more rib fractures have been shown to have a 5-fold increased mortality rate and a 4-fold increased incidence of pneumonia. Effective pain control is the cornerstone of medical therapy for patients with rib fractures. For most patients, this consists of oral or parenteral analgesic agents. Intercostal nerve blocks may be feasible for those with severe pain who do not have numerous rib fractures. A local anesthetic with a relatively long duration of action (eg, bupivacaine) can be used. Patients with multiple rib fractures whose pain is difficult to control can be treated with epidural analgesia.
Adjunctive measures in the care of these patients include early mobilization and aggressive pulmonary toilet. Rib fractures do not require surgery. Pain relief and the establishment of adequate ventilation are the therapeutic goals for this injury. Rarely, a fractured rib lacerates an intercostal artery or other vessel, which requires surgical control to achieve hemostasis acutely. In the chronic phase, nonunion and persistent pain may also require an operation.
Flail chest • A flail chest, by definition, involves 3 or more consecutive rib fractures in 2 or more places, which produces a free-floating, unstable segment of chest wall. Separation of the bony ribs from their cartilaginous attachments, termed costochondral separation, can also cause flail chest. Patients report pain at the fracture sites, pain upon inspiration, and, frequently, dyspnea. Physical examination reveals paradoxical motion of the flail segment. The chest wall moves inward with inspiration and outward with expiration. Tenderness at the fracture sites is the rule. Dyspnea, tachypnea, and tachycardia may be present. The patient may overtly exhibit labored respiration due to the increased work of breathing induced by the paradoxical motion of the flail segment.