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in 1896. Hill performed the first cardiorrhaphy in the United States in
1902 and initiated the modern treatment of the wounded heart.
Penetrating trauma to the thoracic vessels was not extensively reported
until the 20th century because of the absence of survivors. In 1934,
Alfred Blalock was the first American surgeon to successfully repair
an aortic injury. Guidelines for treating thoracic trauma were not
established until World War II.
Additional experience in the treatment of penetrating trauma to the
thorax was gained in later military experiences in different wars.
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.
By far, the most important cause of significant blunt chest trauma is
motor vehicle accidents (MVAs). 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.
Anatomy of chest cavity.
The anatomy of the thoracic cage encompasses the area beneath the
clavicles and superior to the diaphragm, bound laterally by the rib
cage, anteriorly by the sternum and ribs, and posteriorly by the rib and
vertebral bodies. Entry into the thorax may be made by sternotomy;
thoracotomy (incising between selected ribs, most commonly the
fourth and fifth) on either the right or left side; or a clamshell incision,
consisting of left and right thoracotomy incisions traversing the
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sternum to join the two. Particular care must be exercised laterally
near the sternum, where the internal thoracic (mammary) artery lies 24 cm on either side. Similarly, remember that immediately inferior to
each rib body are the intercostal artery, vein, and nerve, from which
voluminous bleeding can occur. Patients have required reexploration
for injuries to these various vessels and have exsanguinated as a result
of missed injuries to these vessels.
Anteriorly, injuries to the heart should be presumed to have occurred
if entry points are present anywhere between the 2 midclavicular lines.
On occasion, significant injury to the heart has occurred from entry
points lateral to these margins, as in gunshot or missile injuries.
Exceptionally long penetrating instruments and weapons (e.g., arrows,
swords, lances) can also directly penetrate the heart from a distant
entry point. Similarly, injuries to any of the intrathoracic structures
can be effected with long penetrating devices; consider the possibility
of injuries to the diaphragm, great vessels, or posterior mediastinal
structures in these cases. The right atrium and right ventricle are the
anterior portions of the heart; these areas are the primary sites
involved in penetrating injuries of the heart.
Mechanism of injury
The mechanism of injury may be categorized as low, medium, or high
velocity. Low-velocity injuries include impalement (e.g., knife wounds),
which disrupts only the structures penetrated. Medium-velocity
injuries include bullet wounds from most types of handguns and airpowered pellet guns and are characterized by much less primary tissue
destruction than wounds caused by high-velocity forces. High-velocity
injuries include bullet wounds caused by rifles and wounds resulting
from military weapons.
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Shotgun injuries, despite being caused by medium-velocity projectiles,
are sometimes included within high-velocity projectile injuries. The
amount of tissue damage is directly related to the amount of energy
exchange between the penetrating object and the body part.. The
expansion of the tissue particles away from the pathway of the bullet
creates a temporary cavity. Because this cavity is temporary, one must
realize that it was once present in order to understand the full extent of
injury. Penetrations from blast fragments or from fragmentation weapons
can be particularly destructive because of their extremely high velocities.
The clinical consequences depend on the mechanism of the injury, the
location of the injury, associated injuries, and underlying illnesses.
Organs at risk, in addition to the intrathoracic contents, include the
intraperitoneal viscera, the retroperitoneal space, and the neck.
Any entry wound below the nipples (front) and the inferior scapular
angles (dorsum) should be considered an entry point for a course that
may have carried the missile into the abdominal cavity. Missiles from
gunshot wounds (GSWs) can penetrate all body regions regardless of
the point of entry. Any patient with a gunshot entry wound for which a
corresponding exit wound cannot be identified should be considered
to have a retained projectile, which could embolize to the central or
distal vasculature. A patient with combined intrathoracic and intraabdominal wounds has a markedly greater chance of dying.
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.
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Blunt trauma commonly results in chest wall injuries (e.g., rib
fractures). The pain associated with these injuries can make breathing
difficult, and this may compromise ventilation. Direct lung injuries,
such as pulmonary contusions, 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.
Blunt trauma that causes significant cardiac injuries (e.g., chamber
rupture) or severe great vessel injuries (e.g., 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.
Sternal fractures are rarely of any consequence, except when they
result in blunt cardiac injuries. 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.
Blunt thoracic injuries are devided into 3 broad categories:
I. Chest wall fractures, dislocations, and barotrauma (including
diaphragmatic injuries).
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II. Blunt injuries of the pleurae, lungs, and aerodigestive tracts.
III. Blunt injuries of the heart, great arteries, veins, and lymphatics.
Initial management
As always in trauma, management begins with establishing ABCDE.
Indications for emergency endotracheal intubation include apnea,
profound shock, and inadequate ventilation. Patients with clinical
signs of a tension pneumothorax, immediate chest decompression is
accomplished with either a large-bore needle at the second intercostal
space or, more definitively, with a tube thoracostomy. A sucking chest
wound must be appropriately covered to permit adequate ventilation
and to prevent the iatrogenic development of a tension pneumothorax.
Volume replenishment is the cornerstone of treating hemorrhagic
shock. Continuous infusions of even blood or normotonic fluids cause
significant peripheral tissue edema, frank acute respiratory distress
syndrome (ARDS) or a tremendous increase in lung water ("soggy
lungs"), and cardiac compromise. Newer approaches, described in
literature, are emphasizing the use of hypertonic solutions in an effort
to minimize these complications.
Alternatively, several groups have championed the concept of "scoop
and run" when treating injuries at the site of trauma in the field. With
the development of modern emergency medical services, the field care
of injured patients has improved. Rapid assessment to identify lifethreatening injuries along with key interventions, namely management
of the airway and control of hemorrhage, and avoidance of massive
volume increases before rapid transport to the closest appropriate
facility is the current standard of care.
This is in contrast to the concept of "stay and play," during which
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trained personnel make major triage and treatment decisions in the
field. If the patient has persistently low systemic pressure, a source of
ongoing blood loss or some other mechanisms to explain the
hypotension (e.g., cardiac tamponade, tension pneumothorax) should
be preferentially sought. Additionally, some data suggest that continued
volume resuscitation before surgical control of bleeding may worsen
both the bleeding process and final outcome. Fluid collections in
either hemothorax should be treated with percutaneous thoracostomy
tubes.
The workup includes the following:
Laboratory Studies
Complete blood cell count
A complete blood cell (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 (ABG).
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
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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 chlorideresponsive metabolic alkalosis or hyperchloremic metabolic acidosis.
Coagulation profile
The coagulation profile, including prothrombin time/activated partial
thromboplastin time, fibrinogen, fibrin degradation product, and Ddimer 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 creatine kinase isoenzyme levels
Measurement of serum myocardial muscle creatine kinase isoenzyme
(creatine kinase-MB) levels is frequently performed in patients with
possible blunt myocardial injuries. The test is rapid and poorly sensitive.
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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 cross match 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.
Imaging Studies
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, hyperresonant
hemithorax, and signs of hemodynamic compromise (i.e., 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
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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.
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.
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
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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.
Diagnostic Tests and Procedures
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.
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