Emergency Medicine

Thoracic Trauma: A Case-Based Review

A woman who has been in a motor vehicle crash, a young man who was stabbed in the chest, and an elderly man who fell in his bathtub serve to illustrate the diagnosis and management of three major types of thoracic trauma.

By Gigi Madore, MD, and Eric Legome, MD

Thoracic injuries account for more than 16,000 deaths annually in the United States—or up to a quarter of all trauma deaths. While sudden death often results from complete aortic transection or myocardial wall rupture, many other deaths from thoracic trauma are preventable if they are recognized and managed appropriately. This article will focus on the diagnostic tools available to emergency physicians in their approach to patients with suspected thoracic injuries. Using a case-based scenario, three specific problems will be considered: aortic rupture, pneumothorax, and rib fractures in the elderly. In each of these conditions, prompt diagnosis and treatment can be lifesaving.

AORTIC RUPTURE

A 36-year-old woman presents to the emergency department after a high-speed motor vehicle collision with a tree. She was the driver and was wearing a seat belt; the airbag deployed in the collision. She complains of severe anterior chest pain and has a large area of ecchymosis on her chest. Her vital signs are stable and her FAST (focused assessment by sonography for trauma) exam is negative for free intraperitoneal or pericardial fluid, but the possibility of an aortic injury is a grave concern.

Here are some key questions to consider:

What are the clinical findings with aortic rupture? The most common symptoms of traumatic aortic rupture include chest pain, dyspnea, back pain, hoarseness, dysphagia, and cough. Clinical signs of possible aortic injury include unexplained hypotension, upper limb hypertension, acute coarctation syndrome (decreased lower limb pulses with normal upper limb pulses), a systolic murmur audible over the base of the heart or between the scapulae, and a palpable supraclavicular hematoma.

How useful is chest radiography in the evaluation of suspected aortic rupture? Chest radiography remains a valuable tool in excluding the diagnosis of aortic rupture in some cases. Most patients with aortic injuries will exhibit radiographic signs of mediastinal hemorrhage, which is associated with aortic injury. This type of hemorrhage is not usually from the aortic injury itself but the result of mediastinal bleeding from blunt or deceleration injury to the mediastinal venous structures.

An upright posteroanterior (PA) chest x-ray is superior to a supine anteroposterior (AP) x-ray. Alternatively, an upright AP x-ray with 15 degrees of forward angulation is usually sufficient to evaluate the mediastinal contour. However, because these patients are invariably immobilized, the chest x-ray taken during the primary survey is most often with the patient supine. A PA x-ray should generally not be the only study used to exclude aortic rupture in the patient with significant chest trauma.

An abnormal chest radiograph has high sensitivity but low specificity for traumatic aortic injury. In fact, patients with mediastinal hemorrhage have no more than a 20% probability of aortic injury. Numerous factors account for this: supine radiographs that widen and distort the mediastinum; atelectasis, pleural effusions, and lung contusions and hematomas that obscure the mediastinal margins; limited technical quality, motion artifacts, and overlying support tubes and lines; mediastinal lipomatosis; vascular anomalies and thoracic scoliosis; and, most commonly, mediastinal hemorrhage without vascular injury.

Can a normal chest radiograph rule out an aortic injury? The utility of a negative chest x-ray remains controversial. A truly normal PA chest radiograph has a very high negative predictive value for aortic injury (approximately 99%). Some signs, however, are relatively obscure or occult and may be missed on the initial interpretation. Other injuries may make a PA chest radiograph difficult or imprudent to obtain. Therefore, when the suspicion for aortic rupture remains high due to a high-speed or significant deceleration injury, a normal chest x-ray warrants further diagnostic studies. Certainly any finding on the x-ray suggesting possible aortic rupture, no matter how nebulous, requires further evaluation for this potentially devastating injury.

Can computed tomography (CT) rule out aortic injuries? Chest CT is considered the standard diagnostic test for suspected aortic injury because it is widely available and has extremely high sensitivity and specificity. In most cases, a negative chest CT using intravenous (IV) contrast can exclude an aortic injury. The majority of patients with complete transection or active aortic bleeding die at the scene. Patients who survive to the hospital will not have these overt findings, but they will have evidence of pseudoaneurysm or luminal disruption on CT. Pseudoaneurysm is an incomplete and
highly unstable tear in the aortic wall, in which arterial blood is contained by only the adventitial layer of the aorta. Other CT signs of traumatic aortic injury include one or more of the features listed in the box below.

A patient with an isolated anterior mediastinal hematoma can usually be cleared of aortic injury, although there remains some controversy on this point. In general, if there is a reason for the hematoma, such as a sternal or thoracic fracture, then aortic injury can usually be ruled out radiographically. If there is no clear cause, however, some centers will consider the CT scan equivocal and follow up with an angiogram to rule out a subtle contained rupture.

Studies of patients who underwent CT followed by confirmatory aortography validated the accuracy of CT scanning, especially the newer helical and multidetector CT, in the evaluation of suspected aortic injuries. The sensitivity and negative predictive value of chest CT approaches 100%, supporting the use of CT to reliably exclude aortic injury. The sensitivity decreases slightly if only direct signs of aortic injury are used. The specificity of CT varies more, depending on how a positive finding on CT is defined. When a positive finding is defined as periaortic hematoma or direct signs of aortic injury, the specificity is approximately 95%. Specificity can be further increased to almost 100% when only direct signs of aortic injury define a positive finding.

Is an angiogram necessary if the CT is positive? Aortography is best reserved for patients with equivocal or indeterminate CT scan results. While an angiogram is the gold standard for diagnosing aortic rupture, chest CT has proved to be extremely valuable as a screening and diagnostic tool, with close to 100% sensitivity and negative predictive value for traumatic aortic injury. Chest CT is faster, less expensive, and less invasive than aortography. Computed tomography can avoid a significant number of aortograms, up to 90% in some studies. It also provides the opportunity for patients with unequivocal signs of aortic injury on CT to proceed directly to surgery. When the CT findings are equivocal, an angiogram may still be necessary. In general, however, an angiogram has little value in the setting of a CT scan that is diagnostic of traumatic aortic injury and it delays potentially lifesaving surgical intervention.

What about transesophageal echocardiography (TEE)? Transesophageal echocardiography is another highly accurate method of detecting blunt aortic injury. However, it cannot be used to exclude the diagnosis. Because TEE can be performed at the bedside or in the operating room, it may be particularly beneficial in patients who require immediate surgery or cannot safely endure a CT scan, either because of hemodynamic instability or because contrast dye is contraindicated.

Compared with chest radiography or CT scan, echocardiography is more operator-dependent. It is also contraindicated in patients with suspected cervical or esophageal injuries. It does not visualize the ascending aorta or aortic branches well and consequently may miss injuries to these vessels. Nevertheless, TEE compares favorably with angiography and CT scan in most cases and has even been shown to diagnose some intimal tears not seen on angiography (although the clinical significance of this is unclear). It also has utility in diagnosing valvular injuries and pericardial effusions. With a sensitivity of 100% (assuming an experienced operator) and a specificity of 98%, TEE can be used safely and quickly in critically injured patients with suspected traumatic aortic rupture. The box below provides an overview of diagnostic tests for aortic rupture.

Can aortic repair be delayed in the case of severe head trauma or other serious injuries? The high mortality rate of blunt aortic injury worsens with time. Nearly 80% of aortic ruptures are fatal at the scene. In survivors, the aortic adventitia and mediastinal structures contain the bleeding initially, but frank rupture commonly occurs within 24 hours if the injury goes undiagnosed and untreated. Once aortic injury has been diagnosed, prompt surgical repair is generally the best approach. However, immediate repair may not be possible in all patients, such as those with severe intra-abdominal or head injuries who require other operative procedures. In patients with severe comorbidities, medical management can be initiated immediately and delayed surgical repair should not adversely affect mortality.

Although prospective data are lacking, multiple case series have demonstrated similar or even improved mortality and morbidity rates with delayed repair of blunt aortic injury. Delayed repair, however, mandates strict medical control of aortic wall stress by lowering heart rate with a beta blocker (esmolol or metoprolol) and decreasing blood pressure with vasodilators (sodium nitroprusside, calcium channel blockers, or nitrates), often in combination, to maintain a heart rate of 60 and a systolic blood pressure of about 100 mm Hg. Alternatively, labetolol can be used for its combined alpha- and beta-blocker activity. If signs of actual or impending rupture exist—such as contrast extravasation, pseudocoarctation, rapid enlargement of a pseudoaneurysm, or repetitive large hemothorax—immediate surgical repair is required. If other considerations do not warrant delayed repair, no benefit is gained by postponing surgery.

What are the surgical treatment options? The main surgical options are graft replacement of the ruptured aortic segment or direct suturing of the aortic lesion. Recently, endovascular repair with an endoluminal stent graft has gained popularity; it offers a more rapid and less invasive approach with lower morbidity and mortality. The requirements for endovascular repair include a rupture distal to the left subclavian artery with the proximal neck of the healthy aorta 5 mm or more in length, absence of thrombus in the fixated regions, and vascular access. Many patients meet these requirements and are appropriate candidates for the procedure.

PNEUMOTHORAX

A 24-year-old man arrives in the emergency department after receiving a single stab wound to the left lateral chest at the fourth intercostal space. He is clinically stable and complains only of minor chest discomfort. On physical examination, however, he has decreased breath sounds in the left chest but no subcutaneous air.

Key questions to ask in this case:

What is the most efficient diagnostic test? The standard diagnostic test for pneumothorax remains an upright chest x-ray. While its specificity is extremely high, the negative predictive value is somewhat lower, leading to false negative results in patients who may require further management. The patient in the above scenario suffered penetrating trauma, but in the case of blunt trauma most chest x-rays are obtained with the patient in the supine position, which has an even lower sensitivity. Cadaveric studies demonstrate that up to 400 ml of air must be present in the pleural space to detect a pneumothorax on a supine chest radiograph. A pneumothorax in the supine position tends to accumulate in the anteroinferior aspect of the pleural space. Signs of pneumothorax on a supine radiograph include basal hyperlucency, a deep lateral costophrenic sulcus (see image below), or a “double-diaphragm” appearance.

Radiographic evidence of pneumothorax. This x-ray exhibits a deep lateral costophrenic sulcus, one of the signs of pneumothorax in a supine view.

An expiratory chest radiograph may have improved sensitivity; however, it has not been compared in any trial to the PA radiograph. With CT scanning commonly used now for abdominal and thoracic trauma, many pneumothoraces that were previously missed are now diagnosed on CT. In fact, in one study using CT as the gold standard, chest x-rays missed almost 40% of pneumothoraces. The clinical significance of these “occult pneumothoraces” is unclear, since these patients tend to do well if left untreated.

Standard management of asymptomatic patients with penetrating chest trauma without evidence of pneumothorax on initial chest radiographs is observation with follow-up x-rays 6 to 12 hours later. Such a lengthy interval between radiographs can lead to unnecessary admissions or exacerbate overcrowding in emergency departments and trauma centers. Reducing the interval between observation and follow-up chest x-rays to three hours has been shown to be equally efficacious, although larger studies are needed before adopting this standard of practice. Local cost and space considerations may make it more efficacious to obtain a chest CT rather than a repeat radiograph. Given its ability to detect subtle or occult pneumothoraces, a negative CT scan has a high enough negative predictive value to obviate a repeat plain radiograph or CT.

What is the gold standard for diagnosing pneumothorax? Computed tomography has been considered the gold standard for diagnosing pneumothorax, with a sensitivity and specificity approaching 100%. Also, in blunt trauma patients with a significant mechanism of injury, a CT scan can diagnose hemothorax (including active bleeding), aortic injury, rib fractures, spinal fractures, pulmonary contusions, scapular fractures, and pericardial effusions. Chest CT may have only minimal benefit in isolated lateral penetrating thoracic trauma.

Can ultrasound be used to detect pneumothorax? Multiple recent papers have described the use of ultrasound as a rapid diagnostic tool for traumatic pneumothorax. In several centers with experienced surgical or emergency physician sonographers, the sensitivity for diagnosing pneumothorax by ultrasound approaches 100%, which is much higher than supine AP chest radiographs (sensitivity 36% to 76%, with CT or rush of air as the gold standard). Although not yet the standard of care, ultrasound has proven to be a widely available, rapid, accurate, and inexpensive diagnostic test for the presence of pneumothorax. Unlike CT, it does not require that the patient be removed from the emergency department and its resuscitative resources. Furthermore, it allows for the differentiation between small, medium, and large pneumothoraces.

Ultrasound is potentially most useful in rapidly excluding the diagnosis of pneumothorax in unstable patients with multiple injuries. The major factor obscur-ing the diagnosis seems to be subcutaneous emphysema, although this is often diagnostic of pneumothorax in the right clinical setting.

The ultrasound technique is relatively simple. An ultrasound probe is applied to the anterior chest wall in the second, third, or fourth intercostal space on the mid-clavicular or anterior axillary line. While a high-frequency transducer is ideal, study protocols have included both 7.5- and 2.4- to 4-mHz probes.

Two distinct sonographic features have been identified—“lung sliding” and “comet-tail artifacts”—to diagnose or rule out pneumothorax. In a normal lung, the visceral and parietal pleurae will slide over each other in a to-and-fro movement in synchrony with respirations. This appears as a hyperechoic line between the chest wall and the lung. The absence of normal lung sliding is predictive of a pneumothorax. It may also be absent in patients with adult respiratory distress syndrome or acute lung fibrosis in the absence of pneumothorax (false positive finding), but its presence allows immediate exclusion of pneumothorax.

Likewise, comet-tail artifacts should be present in a normal lung. These are hyperechoic reverberation artifacts, or high-amplitude echoes, arising from the visceral pleura, which taper and diminish in brightness toward the bottom of the screen. Like lung sliding, comet-tail artifacts may be absent in normal lungs but their presence allows for the exclusion of pneumothorax.

What are the management options for pneumothorax? Does the size of the pneumothorax matter? Management options for pneumothorax can be divided into four possibilities: observation; aspiration; use of a Heimlich valve or pigtail catheter; or chest tube thoracostomy. Choosing the most appropriate option often depends on the specific type of pneumothorax present.

For an occult pneumothorax resulting from blunt trauma diagnosed on CT scan, urgent management is not required. The urgency in treating pneumothorax resulting from penetrating trauma is less clear. There are no large prospective studies that look at this issue; however, in retrospective studies of mixed (blunt and penetrating) trauma, there seems to be no significant difference. In general, progression of pneumothorax to a stage that requires chest tube thoracostomy occurs in fewer than 10% of patients. Anterolateral pneumothoraces may have a higher incidence of progression than anterior or lateral pneumothoraces alone.

In some studies, larger pneumothoraces (more than 5 x 80 mm) were more likely to progress. A small symptomatic pneumothorax often responds to simple aspiration or use of a Heimlich valve or pigtail catheter. There is limited research to recommend one particular method. Some centers tend to favor using thoracostomy tubes in all patients, although this may be overly aggressive in some cases. Small visible pneumothoraces can also be managed simply by observation and supplemental oxygen, with invasive measures reserved for failure to reabsorb.

Choice of treatment often depends on physician preference and institutional practice. In general, a large pneumothorax or a pneumohemothorax should be evacuated with tube thoracostomy. Chest tube thoracostomy, however, has been associated with an adverse event rate as high as 21%, including complications related directly to the tube, such as pain, improper positioning, and removal, as well as bleeding, infection or empyema, and length of stay.

What if positive pressure ventilation (PPV) is required? Current evidence is sparse in directing the proper management of ventilated trauma patients with an occult pneumothorax diagnosed by CT. Advanced Trauma Life Support protocols advocate tube thoracostomy for these patients. A few small prospective studies have focused specifically on this question but have come to different conclusions and recommendations. Enderson and colleagues randomized 40 patients with occult pneumothoraces to tube thoracostomy versus observation without regard for need for PPV. Eight of 21 patients observed (38%) had progression of their pneumothoraces on PPV, with three developing tension pneumothorax. None of the patients with tube thoracostomy suffered major complications as a result of the procedure, regardless of the initial size of the pneumothorax.

A more recent study by Brasel randomized 39 patients with 44 pneumothoraces to tube thoracostomy versus observation, with nine patients in each group requiring PPV. Only two of the nine patients receiving PPV treated with observation required tube thoracostomy, which was similar to those not on PPV, suggesting that observation is reasonably safe regardless of the need for PPV or the size of the pneumothorax. It is possible that differences in ventilatory management contributed to the lack of clinically significant pneumothorax progression in these patients compared with those in the Enderson trial. Nevertheless, it seems reasonable to observe small pneumothoraces under PPV in the intensive care unit if patients are able to tolerate brief episodes of hypotension should a tension pneumothorax develop. Any patient with significant underlying cardiac disease or pulmonary injury or disease would probably benefit from prophylactic tube thoracostomy, as would anyone undergoing surgery.

Are prophylactic antibiotics required after tube thoracostomy? While the evidence is weak, a meta-analysis and several prospective studies support the prophylactic use of a first-generation cephalosporin for up to 24 hours to decrease the incidence of pneumonia but not empyema in trauma patients receiving tube thoracostomy.

How can cardiac injury be excluded in the presence of stab wounds in the proximity of the heart? Among the most lethal of all forms of trauma, cardiac injuries can present variably with hemodynamic instability, cardiovascular collapse with shock, or frank cardiac arrest. Acutely, as little as 150 ml blood can lead to tamponade. Cardiac lacerations due to penetrating trauma are associated with high morbidity and mortality. In the right clinical setting, physical exam findings, especially decreased heart sounds, distended neck veins, and hypotension (Beck’s Triad), can be diagnostic. In reality, this rarely occurs and the diagnosis of pericardial or cardiac injury must be made by diagnostic testing or surgical exploration.

Surgical creation of a subxiphoid pericardial window is the gold standard for diagnosis of pericardial injury. However, because this is a highly invasive procedure with a high morbidity, it has essentially disappeared from emergency practice. While removal of 10 to 15 ml of blood can be lifesaving, it is unclear how well pericardiocentesis works in this setting, although it may be attempted as a lifesaving measure.

Limited bedside echocardiography that evaluates solely for evidence of pericardial fluid and tamponade can provide immediate and reliable information regarding the pericardium and the need for emergent surgery. Emergency physicians, surgeons, cardiologists, and cardiac sonographers are highly accurate at diagnosing or ruling out pericardial effusion by bedside ultrasound. Depending on the expertise of the sonographer, this may be the definitive modality, although if there is also a hemothorax, a confirmatory study should be considered. Chest CT, while not a first-line test, is reasonably accurate in diagnosing pericardial effusion (hemorrhage) and may also show secondary signs of tamponade, including venous distension (of the inferior or superior vena cava or hepatic veins), periportal lymphedema, or compression of the right ventricle.

RIB FRACTURES IN THE ELDERLY

An 80-year-old man presents to the emergency department after a fall in his bathtub. He complains of left anterior rib pain with point tenderness and bony crepitus, and he has mild difficulty with deep inspiration. His oxygen saturation level is normal. A chest radiograph reveals lateral fractures of the fourth through sixth ribs. The patient has a stable home environment.

Key questions to consider:

Why should we be concerned about thoracic trauma in the elderly? Elderly patients with thoracic trauma often have poor outcomes despite seemingly minor injuries, such as rib fractures and pulmonary contusions. Osteoporosis, decreased strength or conditioning, poor vision or balance, and chest wall rigidity increase susceptibility to chest wall trauma in this population. These age-related changes, coupled with decreased immunity, lead to a greater incidence of pulmonary complications. Underlying poor pulmonary reserve contributes to worsened outcomes with rib fractures and pulmonary contusions.

Rib fractures are very common injuries, accounting for up to 10% of admissions to trauma services. The mechanism of injury for more than half of patients 65 years of age or older admitted with rib fractures is a low-velocity fall, compared to less than 1% of patients younger than 65, underscoring the fact that less force is necessary to fracture ribs in the elderly.

Elderly patients with rib fractures who require admission have twice the mortality and thoracic morbidity of younger patients with similar injuries. The most frequent complications include pneumonia, late pulmonary effusion, acute respiratory distress syndrome, and lobar collapse. Pulmonary contusion is the most common associated finding.

The increased mortality in elderly patients who suffer rib fractures can be attributed not only to diminished physiologic reserve but also to the increased prevalence of comorbid conditions. However, even after comorbidities are controlled for, elderly patients admitted with rib fractures have a higher mortality than younger patients, despite a lower injury severity. For these reasons, when rib fractures are suspected, it is crucial to completely disrobe the patient. In addition to observing, palpating, auscultating, and measuring respiratory rate and pulse oxygenation, a chest radiograph should be taken. Rib films are often ordered, but there are no clear guidelines for their diagnostic role. They may be useful if there is suspicion for multiple fractures after a negative chest x-ray, but they should not be considered the standard of care.

What is the morbidity and mortality associated with rib fractures in the elderly? In one study, patients aged 65 years and older with three or four rib fractures experienced a 19% mortality rate and 31% rate of pneumonia. Mortality and pneumonia rates increase with the number of rib fractures. For elderly patients with more than six rib fractures, the mortality and pneumonia rates increase to 33% and 51%, respectively. The occurrence of pneumonia is an independent predictor of early death. The high complication rate and cost in caring for elderly patients with three to six rib fractures is demonstrated in the dramatic increase in the number of ventilator days, intensive care unit days, and length of stay compared with younger patients with a similar severity of injury.

While elderly patients are particularly vulnerable to the effects of blunt thoracic trauma, rib fracture morbidity begins to increase in patients as young as 45 years of age—significantly younger than generally appreciated. Holcomb and colleagues found that morbidity from rib fractures increases in patients older than 45 with more than four rib fractures, compared to similar patients with four or less fractures. In addition, patients with multiple pre-existing medical conditions, even if they have less than four rib fractures, have significantly increased mortality compared with younger healthy patients.

Can elderly patients with rib fractures be discharged safely? Patients with three rib fractures should be seriously considered for hospitalization; those with more than three rib fractures should be admitted. Physicians must maintain a low threshold for admitting any elderly patient with fewer than three rib fractures and multiple comorbidities.

Key factors in the care of elderly patients with thoracic trauma include early aggressive pain control and respiratory care to prevent pulmonary complications. Local rib blocks are an underused modality for controlling pain. Inpatient management often consists of blocks along with epidural anesthesia, which is preferable to IV opioid pain medications. Patients who are discharged should be given an incentive spirometer to prevent atelectasis and pneumonia, in addition to adequate pain control.