A 37-year-old man is brought to the emergency department after being involved in a high-speed motor vehicle collision. The patient’s vehicle crashed into a tree when he fell asleep at the wheel. The patient was restrained, his vehicle sustained severe front-end damage, and the air bags deployed in the vehicle. In the emergency center, his vital signs were blood pressure 110/80 mm Hg, pulse 110 beats/min, respiration rate 28 breaths/min, and Glasgow Coma Score (GCS) 14. The primary survey revealed a patent airway, diminished breath sounds on the left with exquisite chest wall tenderness, and subcutaneous emphysema. The heart sounds are normal and there is no jugular venous distension. The secondary survey revealed no abdominal tenderness, a stable pelvis, and no extremity abnormalities. A chest radiograph revealed several rib fractures on the left, a large pulmonary contusion, a left pneumothorax, and widening of the mediastinal structures.
What are the most likely diagnoses?
How would you confirm the diagnosis?
ANSWERS TO CASE 16: Chest Trauma (Blunt)
Summary: A 37-year-old man presents with multiple blunt chest injuries following a high-speed motor vehicle collision. In addition to injuries that have already been demonstrated by chest radiography, a major concern at this point is the possibility of thoracic aortic disruption.
• Most likely diagnoses: Blunt chest trauma with pulmonary contusion, pneumothorax, rib fractures, and possible thoracic aortic disruption.
• Confirmation of diagnosis: All of the diagnoses except for the aortic injury have been confirmed by chest radiography. The aortic injury can be diagnosed by angiography, CT angiography, or transesophageal echocardiography.
1. Know the priorities in the treatment of patients with multiple blunt traumas.
2. Learn the diagnosis and treatment of pneumothorax, pulmonary contusion, and thoracic aortic injury following blunt trauma.
The initial assessment of the patient should begin with the airway, breathing, and circulation (ABCs), followed by the secondary survey. Simultaneously, intravenous lines should be placed, blood collected, and vital signs monitored. With the presence of diminished breath sounds, chest wall tenderness, and left-sided soft tissue crepitation, it would have been appropriate to place a left chest tube even without radiographic confirmation of left pneumothorax. Reassessment of the patient’s respiratory status should be made and repeated chest radiographs obtained immediately following chest tube placement. If the patient’s respiratory status worsens or fails to improve dramatically, intubation should be considered to help improve cardiopulmonary stability while efforts are made to identify other potential life-threatening injuries. Once all the injuries have been identified (Table 16–1), they can be addressed according to their urgency.
Table 16–1 • CAUSES OF INSTABILITY AFTER BLUNT CHEST TRAUMA
APPROACH TO: Blunt Chest Trauma
In the evaluation and treatment of patients with blunt chest trauma, it is critical to assess the magnitude of energy transfer that the accident has delivered to the injured victim. For instance, patients involved in a frontal impact collision with the deployment of air bags should be presumed to have absorbed a tremendous amount of kinetic energy to the chest wall and underlying structures. After the ABCs have been assessed, a secondary survey accomplished, and intravenous lines and blood studies performed, the patient should be examined for any change in clinical status (ie, mental status, vital signs, respiratory status). Often, subtle changes forebode a looming catastrophe and require prompt reevaluation. As the assessment continues and injuries are identified, prioritizing attention depends on the severity and type of injury. A simple question to ask is “What will kill the patient first?” and address these issues first (Table 16–2).
Table 16–2 • ASSESSMENT OF CASE NO. 16’s INJURIES, DIAGNOSIS, AND TREATMENT
The identification of rib fractures, especially fractures of the upper ribs (first and second), may indicate the presence of more severe associated injuries such as vascular injuries. The treatment of rib fractures is focused on management of the associated pain and the chest wall splinting that may lead to hypoventilation, atelectasis, and pneumonia. Therefore, adequate pain control may require the use of epidural anesthetic.
Pneumothorax as identified by the chest radiograph results from disruption of the pleural surface. In general, simple traumatic pneumothorax may have been caused by a fractured rib penetrating the pleura or by direct injury to the pulmonary parenchyma. Proper insertion of a chest tube (tube thoracostomy) into the pleural space generally results in reexpansion of the lung parenchyma. If the lung fails to reexpand after chest tube placement and significant air leakage is noted, one should consider the possibility of a major tracheobronchial injury.
Blunt cardiac injury may range from myocardial contusion to cardiac rupture. When this occurs, 40% present with arrhythmia, 45% with cardiogenic shock, and 15% with anatomic defects; most patients with cardiac defects die before reaching the hospital.
Figure 16–1. Diagnostic strategy for patients suspected of traumatic rupture of the aorta. NG, nasogastric.
Pulmonary contusion results from hemorrhage into the alveolar and interstitial spaces. The clinical condition is determined by the severity of the injury and the extent of lung parenchyma involved. Severe pulmonary contusions may result in significant shunting and hypoxia. In general, supportive measures should be undertaken and the decision for ventilatory support made on clinical grounds. Because of capillary leakage, fluid restriction is usually advised but does not take precedence over adequate fluid resuscitation and oxygen delivery. This injury occurs most commonly from direct compression of the heart between the thoracic wall and the spine.
In the case of blunt chest trauma, a widened mediastinum as revealed by a screening chest radiograph should raise a suspicion for traumatic rupture of the aorta (TRA) (Figure 16–2). Although TRA is classically considered in the case of frontal impact (acceleration-deceleration) injuries, 25% of TRAs occur as a result of side impact collisions. The outcome with TRA is determined by whether the rupture is contained by the mediastinal pleura. Most patients with a free rupture into the pleural space die at the scene of the accident and never arrive at a hospital to receive medical attention. Thus, those who arrive for medical attention may need immediate diagnosis and treatment to prevent impending rupture. Debate exists as to the best tool for diagnosis. CT angiography has become the most commonly applied diagnostic study for the identification of TRA. Transesophageal echocardiography, not mentioned in the algorithm, can be used for diagnosis but remains operator dependent and is relatively invasive.
Figure 16–2. Traumatic rupture of the aorta. A widened mediastinum (open arrow) on the chest radiograph of a patient who had blunt trauma to the descending aorta. The left mainstem bronchus is depressed (solid arrow). (Reproduced, with permission, from Mattox KL, Feliciano DV, Moore E. Trauma. 4th ed. New York, NY: McGraw-Hill; 2000:562.)
The management of patients with TRA includes immediate medical management that includes the initiation of pharmacological agents to keep systolic BP approximately 100 until definitive repair. The definitive approach to TRA includes open repair, endovascular repair, and nonoperative management depending on the injury type, resource availability, and patient conditions and comorbidities. The outcomes related to these treatment options have never been evaluated by randomized controlled studies, and treatment outcomes have only been compared retrospectively. Endovascular repair has a number of advantages in comparison to open repairs. Most endovascular repairs are performed without the need for systemic anticoagulation. Endovascular repairs are also advantageous over open repairs in that they do not require thoracotomy or single-lung ventilation. In a recently published collective review, the mortality rates reported were 9%, 19%, and 46% for endovascular repair, open repair, and nonoperative management, respectively. The comparison of open and endovascular repairs has shown endovascular repairs to be associated with significantly lower rates of spinal cord ischemia, renal injuries, and graft infections.
16.1 A 16-year-old adolescent boy is brought into the intensive care unit (ICU) for multiple blunt trauma approximately 12 hours previously. His injuries included a femur fracture. He is noted to have a Po2 of 60 mm Hg, despite the use of 100% oxygen by rebreather mask, and has become confused. The chest radiograph reveals clear lung fields and a normal cardiac size. Which of the following is the most likely diagnosis?
A. Pulmonary contusion
B. Fat embolism
D. ICU psychosis
E. Occult pneumothorax
16.2 A 43-year-old man is involved in a motorcycle accident in which his bike slipped on wet pavement. He is brought into the hospital and noted to have multiple rib fractures, a tibial fracture, and significant contusions. The cardiac monitor reveals multiple premature atrial contractions. Which of the following is the most likely etiology for the cardiac arrhythmias?
B. Lower extremity fractures
C. Rib fractures
D. Blunt cardiac injury
E. Caffeine-induced arrhythmias
16.3 A radiologist evaluates a chest radiograph of a 19-year-old woman who was upended while riding her bicycle by a pickup truck. Which of the following findings is most likely to suggest a diagnosis of ruptured thoracic aorta?
A. A loss of aortic knob contour
C. Thoracic transverse process fracture
D. Fracture of the sternum
E. Markedly enlarged cardiac silhouette
16.4 Which of the following remains the gold standard in diagnosing TRA?
A. CT angiography
B. Magnetic resonance imaging
C. Chest radiograph
E. Transthoracic echocardiography
16.1 B. Fat embolism syndrome is an exceedingly uncommon problem that may occur with major long bone fracture, and it can cause hypoxemia and central nervous system effects such as confusion or coma. Other findings include petechiae and retinal lesions. Pulmonary contusion is a possibility in patients with blunt chest injuries; however, patients with pulmonary contusions generally have chest x-ray findings of nonanatomic opacification. Pulmonary atelectasis generally has chest x-ray finding as well. Occult pneumothoraces are pneumothoraces that are small and not seen by chest x-ray; such a finding should not contribute to the clinical findings that are described.
16.2 D. Blunt cardiac injuries may result in tachyarrhythmias or cardiac (pump) failure. Rib fractures are associated with pain, atelectasis, and pneumonia but rarely with atrial arrhythmias. Caffeine is a stimulant that could produce arrhythmias, but in a patient with these findings following severe blunt chest injuries, we should not be too quick to assume that this is the cause.
16.3 A. Chest radiographic findings consistent with thoracic aortic rupture include apical cap, deviated nasogastric tube, obliteration of the aortic knob, and hemomediastinum (not pneumomediastinum).
16.4 D. Aortography is considered the gold standard for diagnosis of TRA, although at most centers CT angiography is used as the initial diagnostic study. Transesophageal echocardiography is also used at some centers. Transthoracic echocardiography is less useful, because this approach provides excellent views of the heart but does not provide visualization of the descending thoracic aorta.
Understanding the amount of energy absorbed by the injured victim is important in treating blunt trauma victims.
The approach to chest trauma is to prioritize by identifying the injury that will kill the patient first (after the ABCs are assessed): tension pneumothorax, pericardial tamponade, hypovolemia from exsanguination.
Identification of rib fractures, especially fractures of the upper ribs (first and second), may indicate the presence of more severe associated injuries (ie, vascular injuries).
A widened mediastinum on a chest radiograph in a patient who has undergone blunt chest trauma, including injury in a deceleration accident, strongly suggests TRA.
CT angiography and aortography are both effective tests to confirm TRA.
Endovascular repair of TRA has emerged as the preferred repair for many of the critically ill patients with this injury.
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