 Lesson 18, Volume 15—Blunt Chest Trauma
By Edward Y. Sako, MD, PhD
Effective December 31, 2004, PCCU Volume 15 is available for review purposes only. CME credit for this volume is no longer being offered. Objectives
- Outline the morbidity and mortality associated with blunt chest
trauma.
- Discuss the initial approach to and assessment of a patient
with blunt chest trauma.
- Describe the pathophysiology of the major injuries incurred.
- Outline treatment methods.
- Discuss newer modalities in diagnosis and treatment.
Key words
airway disruption; aortic injury; cardiac injury;
chest trauma; lung injury; trauma resuscitation
Approximately 20% of trauma
cases per year in the United States include significant chest trauma
as a component. Two thirds of major chest trauma cases are related
to motor vehicle accidents. Twenty-five percent of injuries in
motor vehicle accidents involve the chest. A study by the North
American Major Trauma Outcome Study revealed that approximately
70% of trauma cases are blunt in nature. Approximately 50% of chest
trauma injuries are related to the chest wall.1
It is estimated that approximately 6,000 disability
days per 100,000 persons per year are related to chest trauma.
It is also noted that > 80% of patients with significant blunt
chest trauma also had extrathoracic injuries. The thrust of this
article, however, will focus on blunt chest injuries.
A key to the management of patients with blunt thoracic
trauma is a high index of suspicion for thoracic injury. This is
based on the history, including knowledge of the type and force
of injury, and sometimes subtle findings on clinical examination.
The majority of such injuries may be diagnosed with relatively
simple tests such as chest radiographs. Furthermore, treatment
is often straightforward, using such modalities as tube thoracostomy
or selective use of positive pressure ventilation. Emergency department
physicians and trauma surgeons generally carry out much of the
initial assessment and treatment. However, it is important for
critical care specialists to be aware of the spectrum of injury
in blunt thoracic trauma and know that such injuries may not be
immediately apparent in the initial phases of assessment.2,3
The pathophysiology of blunt thoracic trauma usually
involves alterations in respiration resulting in hypoxia and hypercarbia.
There may be hemodynamic consequences related to injuries to the
heart as well as blood loss from great vessel injury.
The following is largely based on a practical approach
to chest trauma as advocated by the American College of Surgeons
Committee on Trauma via their Advanced Trauma Life Support course.4
Initial Resuscitation
The initial resuscitation is focused on the "ABCs"—airway,
breathing, and circulation—applied in all major trauma resuscitation
cases. This is aimed at rapidly trying to stabilize the patient
while assessing and treating major life-threatening injuries. With
regards to blunt chest trauma, the major injuries discussed below
are those that involve the ABCs and may be fatal within minutes.
Airway Obstruction
Airway patency and air exchange can be assessed by
examining for air movement and watching chest excursion, listening
for stridor, and looking for obvious lower neck or upper chest
injuries that may compromise the airway. If airway patency or the
patient’s ability to protect the airway are in question, a
more secure airway is needed. Endotracheal intubation is the first
step, with care taken to protect against cervical injury. If an
airway injury is suspected, rapid evaluation by means of flexible
bronchoscopy may be necessary to identify the injury. Furthermore,
bronchoscopy may be an aid in obtaining a patent airway, particularly
in the patient who may have an unknown cervical spine injury. Emergency
airway maneuvers such as cricothyroidotomy may also be necessary
during this period.5
Open Pneumothorax
This refers to an opening in the chest wall large
enough to disrupt the negative intrathoracic pressure required
for spontaneous ventilation. Initial treatment may include positive
pressure ventilation and/or rapid covering of the open wound with
evacuation of the pleural space via tube thoracostomy.
The technique of tube thoracostomy has been described
well.3,5 For chest trauma cases, large-bore (> 32F)
tubes are recommended for better evacuation of blood and other
fluids. For related reasons, tubes are usually positioned posteriorly,
in a dependent position for the supine patient.
Flail Chest
This is the result of an injury of the chest wall
significant enough to include multiple ribs resulting in a "free-floating" portion
of the chest wall. Three major pathophysiologic events occur because
of this. The first is interruption of the normal negative intrathoracic
pressure needed to effect spontaneous ventilation as a result of
the paradoxical motion of the flail portion of the chest wall.
The more significant injury, however, is usually underlying pulmonary
contusion, which leads to hemorrhage and edema of the injured lung.
Finally, the amount of associated pain will often result in splinting
with subsequent hypoventilation. The immediate threat to life depends
on the amount of chest wall involved and the extent of the contusion.
Treatment is centered on an assessment of the degree of pulmonary
insufficiency with ventilator support as indicated. Rarely is physical
stabilization of the chest wall necessary.
Tension Pneumothorax
Injury to the visceral pleura of the lung or other
portions of the upper airway may result in a rapid, one-way accumulation
of air within the pleural space. Eventually, intrapleural pressure
increases and causes compression of the mediastinal structures.
The end result is depression of venous return to the heart, resulting
in significant hemodynamic instability. Hallmarks include decreased
breath sounds on the affected side, deviation of the trachea away
from the affected side, and marked hypotension. Diagnosis is generally
clinical, and not radiographic. Treatment consists of rapid evacuation
of the air within the pleural space. This may be done initially
with something as simple as a needle or intrevenous catheter. Tube
thoracostomy then follows. This situation is exacerbated by the
presence of positive pressure ventilation. More definitive treatment
generally depends on the nature of the injury.2,3,5
Massive Hemothorax
Large amounts of blood accumulated within the pleural
cavity will cause hypovolemia and hypotension. Sources of bleeding
may include lung parenchyma, great vessels, or chest wall vessels
such as the intercostal artery. The presentation is shock associated
with absent breath sounds on the affected side(s). Dullness to
percussion may also be present, although this finding is difficult
to elicit in most resuscitation settings. Treatment consists of
rapid evacuation with large pleural chest tubes. Once the initial
accumulation of blood is evacuated, continued blood output from
the chest tube is monitored. The most important treatment during
the resuscitative period is rapid volume replacement. Definitive
therapy requiring thoracotomy is usually undertaken if the rate
of chest tube output is > 100 mL every 30 min. Usually this
is performed by a trauma or thoracic surgeon under controlled conditions
in the operating room.
Cardiac Tamponade
While this injury is more common in penetrating trauma,
blunt chest trauma also may result in rupture of a cardiac structure.
It may be of a degree that does not result in rapid and fatal exsanguination
immediately, but rather causes so much blood to accumulate within
the pericardium that it begins to exert pressure on the heart.
The most susceptible areas are the vena cava and atria, resulting
in depressed venous return to the heart and subsequent hemodynamic
instability. Classically the diagnosis can be made by Beck’s
triad: increased jugular venous distention (or elevated central
venous pressure, if monitored), muffled heart sounds, and hypotension.
The heart sounds may be difficult to hear in the emergency department.
A globular appearance of the pericardium on a chest radiograph
also may be suggestive of this injury. Initial treatment usually
consists of some type of rapid evacuation of the pericardial space,
either via a pericardiocentesis or subxiphoid pericardial window.8,9
Emergent thoracotomy, also known as a resuscitative
thoracotomy or emergency room thoracotomy, is classically performed
through the left anterolateral approach in the intercostal region
in the lower half of the chest. This allows access to the pericardium
to relieve tamponade. It may also allow open massage of the heart
and clamping of the descending thoracic aorta to try to maintain
blood flow to the cerebral region. Although its benefit has been
described in penetrating chest injuries, multiple other reports
have shown its futility in blunt chest cases. Experiences to date
have found that victims who arrive pulseless and unresponsive to
all other measures have uniformly not responded to emergency thoracotomy.2,3,10
Subsequent Evaluation
Once the initial resuscitation and stabilization
have been completed, a repeat assessment is done. Typically this
is done in a more deliberate manner. In addition to a thorough
physical examination, multiple studies may be performed at this
time.11-13
A chest radiograph is the most common test performed
and should be mandatory in the evaluation of a patient with suspected
chest trauma. Most common injuries may be diagnosed by chest radiograph
alone. Ideally, an upright full inspiratory film is obtained to
avoid the potential creation of a wide mediastinum seen in patients
who are supine and may not be taking a full breath. In some cases,
the chest radiograph may suggest injuries to be diagnosed by other
methods.
Chest CT is becoming a common evaluation method as
CT equipment becomes more available in trauma centers. Some centers
now have dedicated CT scanners in the emergency department. In
addition, scanners have become faster, allowing CT to be used for
the more critically ill patients. The value of CT lies in its ability
to detect occult injuries such as mediastinal bleeding, pericardial
effusion, or other injuries that may not be evident on a standard
chest radiograph.14,15
MRI has not been utilized extensively in the evaluation
of acute trauma patients. The length of time needed to obtain images,
in addition to the concurrent isolation precludes its use in potentially
unstable patients who need close monitoring.
Percutaneous ultrasound has recently been advocated
for evaluation of patients with blunt truncal trauma. This involves
the use of ultrasound by emergency room personnel and trauma surgeons
very early in the evaluation process in a protocol known as Focused
Assessment for the Sonographic examination of the Trauma patient
(FAST). To date, however, its application to blunt chest trauma
has been much more limited, with the possible exception of the
assessment of potential cardiac injury, with the ability to also
rapidly detect significant pericardial effusions. One drawback
is that the acts of obtaining and interpreting the images are very
operator-dependent.16,17 The value of this modality
will lie in the familiarity and experience of a given institution
and its personnel.
Transesophageal echocardiography also may have a
role in the evaluation of blunt chest trauma. It is operator-dependent
but in selected instances, it has been found to be particularly
useful in assessing the descending thoracic aorta for injury and
also for evaluating cardiac structures and function. It does not
permit thorough examination of the aortic arch, however.18
Specific injuries that may be discovered during this
evaluation period are discussed below.
Airway Disruption
Fractures or tears of the upper airway may occur
without causing overt obstruction. However, they may impair ventilation
and oxygenation. The diagnosis starts with an index of suspicion
based on the mechanisms of injury and presenting problems such
as stridor. A pneumothorax with subsequent large air leak following
tube thoracostomy or the presence of mediastinal air are additional
clues. Evaluation is usually carried out with the aid of flexible
bronchoscopy. Definitive treatment will depend on the location
and severity of the injury as well as the resources available.
Temporizing measures include selective intubation and ventilation
beyond the area of injury.19-21
Simple Pneumothorax
Usually diagnosed with a chest radiograph, pneumothorax
represents injury to the visceral pleura of the lung resulting
in air accumulation within the pleura space. This is differentiated
from a tension pneumothorax as the air space is not under pressure
and generally has no hemodynamic significance. Treatment consists
of tube thoracostomy.3
Hemothorax
Blood from a variety of sources may accumulate in
the pleural space. In most cases, the volume is too small to be
hemodynamically significant in terms of volume loss or compression
of the lung or mediastinum. Still, evacuation via tube thoracostomy
is generally recommended. This allows the physician to detect any
persistent bleeding into the pleural space and prevents the organization
of the hemothorax, which can later progress to a fibrothorax with
resultant lung entrapment.
Myocardial Contusion
Myocardial contusion is usually a result of blunt
blows to the anterior portion of the chest, and there is potential
for injury to the underlying myocardium. The diagnosis of myocardial
contusion can often be problematic. The clinician should focus
on the clinical picture, which will depend largely on the type
and extent of injury. Major sequelae include regional wall motion
abnormalities and depressed cardiac function not unlike that seen
with myocardial infarction. Injured areas may also serve as a nidus
for rhythm disturbances. A pericardial effusion may occur, as can
early or late pericarditis. In more severe cases, intracardiac
injury such as ventricular or valvar rupture may be seen. Rather
than relying on rigid criteria, the diagnosis hinges on a strong
index of suspicion and specific tests for the potential sequelae:
monitoring the ECG for the presence of arrhythmias; measuring cardiac
enzymes, which may demonstrate myocardial injury; and using ultrasound
to detect any wall motion abnormalities or intracardiac injury.
Accumulation of pericardial fluid may also be assessed by echocardiography.22 Treatment
is based on the findings. In most cases, therapy is supportive
and is often analogous to management after myocardial infarction.
Pulmonary Contusion
Pulmonary contusion usually results from a severe
blow to the chest that typically causes one or more fractures.
As mentioned previously, most pulmonary contusions are related
to the finding of a flail chest. Even if not readily apparent enough
to be life-threatening on initial evaluation, the resultant hemorrhage,
edema, and inflammation of the affected lung may later result in
decreased oxygenation and impaired ventilation. Treatment is usually
individualized based on the respiratory needs of the patient. If
pulmonary contusion is noted during the initial resuscitation,
mechanical ventilation will usually be necessary. During the subsequent
evaluation, therapy directed at the pulmonary contusion may prevent
initiation of mechanical ventilation with its attendant risks.6,7 Therapy
includes limitation of crystalloid fluid administration, aggressive
pulmonary toilet, and regional pain control.23
Aortic Injury
This is a dramatic injury because of the potential
morbidity and mortality of the condition and its treatment. Typically
this is seen when the mechanism of injury is rapid deceleration,
resulting in differential forces on the proximal descending aorta
between fixed and more mobile portions. Thus, the most common site
of injury is just beyond the ligamentum arteriosum. In those patients
who survive to be evaluated, the injury consists of a tear of the
intima with containment of the blood by the adventitia and surrounding
tissue. A periaortic hematoma results but usually there is no active
bleeding. The hallmark sign is a widened mediastinum seen on chest
radiograph, related to the adventitial hematoma. Diagnosis begins
with a high index of suspicion based on the mechanism of injury,
and a chest radiograph is obtained to identify alterations in the
contour of the mediastinum and overall widening of the mediastinum.
CT scans of the chest may help to delineate the changes seen on
chest radiography, specifically hematoma around the affected portions
of the aorta.24,25 The gold standard for the diagnosis,
however, remains arterial angiography, usually directed at outlining
the entire ascending, transverse arch, and proximal descending
portions of the aorta.26 All of these areas are at risk
for blunt injury to the aorta.
Much has been written in recent years regarding alternative
methods of diagnosis including more sophisticated chest CT scan
techniques and the use of transesophageal echocardiography. In
general, the CT scan has not provided the resolution needed for
many surgeons to adequately localize the injury for subsequent
treatment. Transesophageal echocardiography results are very dependent
on the skill and experience of the operator. In addition, much
of the transverse arch of the aorta is not well visualized with
this modality. However, these tests can be valuable as screening
methods or adjunctive imaging in cases where angiography is delayed
or the findings are not definitive.
Treatment of blunt aortic injuries is usually performed
by qualified trauma or thoracic surgeons. While the threat of rupture
of the hematoma is always present, temporizing measures include
hemodynamic monitoring and aggressive BP control, often aided by
IV beta blockade. With such methods, definitive treatment can be
delayed for hours or days if deemed necessary because of the patient’s
condition or other injuries.
Recently, the use of endovascular techniques has
been expanded to include selective use for tears of the proximal
descending thoracic aorta.27 Briefly, these techniques
involve the percutaneous placement of intraluminal stents within
the region of aortic aneurysms and dissections as an alternative
to operative graft replacement. The morbidity of a transthoracic
approach and the need for aortic cross clamping is eliminated.
This treatment is still considered highly experimental but may
become a viable option for trauma patients.
Diaphragmatic Injury
Diaphragmatic injury typically results from the rapid
increase in intra-abdominal pressure related to an episode of blunt
trauma with subsequent rupture of the diaphragm. This is suspected
based on the mechanisms of injury and radiographic appearance.3,28 As
opposed to the defects seen with penetrating trauma, the defects
in blunt trauma usually are larger and more often result in immediate
herniation of abdominal contents. When the defect is small, herniation
may occur over a period of weeks to months. This gradual occurrence
is related in part to the differential between intrathoracic and
intra-abdominal pressures.
The diagnosis may be difficult in part because the
force of injury is likely to result in multiple organ damage, which
will command the resuscitation team’s attention. The chest
radiograph will often be abnormal, showing opacification within
the affected pleural cavity, air fluid levels, and mediastinal
shift. Compression of the lung may also occur. The findings may
be mistaken for primary lung collapse, pleural fluid, or hematoma.
While rupture of the right diaphragm occurs in about
one third of cases, the liver appears to protect against significant
organ herniation into the right pleural space. Therefore, most
cases seem to involve the left side, and the stomach is the most
common organ involved. Thus, nasogastric tube placement can be
helpful in making the diagnosis by chest radiography alone. Barium
studies of the GI tract are another important diagnostic modality.
It is important to keep diaphragmatic rupture in mind when performing
tube thoracostomy for a suspected hematoma. Digital exploration
of the pleural cavity prior to tube placement may be valuable.
Treatment for acute cases usually involves laparotomy for reduction
of the herniated contents, inspection for other intra-abdominal
injury, and diaphragm repair.
Esophageal Injury
Injury to the esophagus related to blunt external
trauma is usually quite rare. Injury may be the result of rapid
compression of the abdomen, which may raise pressures in the stomach
to such a degree that an intraluminal tear of the esophagus results.
Another mechanism is accelerated insufflation of pressured air
into the esophagus in an attempt to ventilate the patient. Given
the force of injury involved, other organs may be affected, particularly
the trachea, which may also be ruptured.
Clinically, the patient may complain of chest or
abdominal pain; later, signs of sepsis from contamination of the
mediastinum and pleura may be present. Chest radiographs may show
widening of the mediastinum, subcutaneous emphysema, pneumothorax,
hydrothorax, or a combination. Usually the lower esophagus is affected;
rupture is therefore into the left pleural cavity. Tube thoracostomy
for drainage is often performed. If the output is suggestive of
gastric contents or the injury is otherwise clinically suspected,
a contrast study or endoscopy of the upper GI tract is indicated
to evaluate the patient for esophageal injury. Treatment is usually
surgical and should be performed early to minimize contamination
of mediastinum and pleura. Primary repair vs diversion will depend
on the condition of the esophagus, degree of contamination present,
and, in some cases, the length of time from injury to surgery.29
Summary
Blunt chest injury represents a significant component
of the morbidity and mortality from trauma. Injuries range from
those that are an immediate threat to life to more occult lesions,
which will ultimately be just as morbid. Recognition and treatment
depend heavily on a high index of suspicion combined with the appropriate
diagnostic tests.
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- Trinkle JK, Furman RW, Hinshaw MA, et al. Pulmonary contusion:
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