A 44-year-old man is brought to the emergency department after he was found unresponsive at the scene of a high-speed motor vehicle collision. The paramedics report that that he was the unrestrained driver, and the passenger in his car was pronounced dead at the scene. The patient was intubated and rushed to the hospital. On arrival, his blood pressure is 78/40 mm Hg, pulse is 135/min, and pulse oximetry is 96% on mechanical ventilation with 40% oxygen. Rapid infusion of isotonic fluids is initiated. Trauma primary survey reveals an intubated man with appropriate spinal precautions. There is bruising and the imprint of the steering wheel across the anterior chest. The trachea is midline, and breath sounds are clear on the right but diminished on the left. Neck veins are collapsed bilaterally. Heart sounds are normal. All four extremities are pale and cool to the touch. There is no obvious external hemorrhage. Portable chest x-ray shows multiple rib fractures, opacification of the left hemithorax, and a widened mediastinum. ECG shows sinus tachycardia. Which of the following is the most likely diagnosis?

Question

A 44-year-old man is brought to the emergency department after he was found unresponsive at the scene of a high-speed motor vehicle collision.  The paramedics report that that he was the unrestrained driver, and the passenger in his car was pronounced dead at the scene.  The patient was intubated and rushed to the hospital.  On arrival, his blood pressure is 78/40 mm Hg, pulse is 135/min, and pulse oximetry is 96% on mechanical ventilation with 40% oxygen.  Rapid infusion of isotonic fluids is initiated.  Trauma primary survey reveals an intubated man with appropriate spinal precautions.  There is bruising and the imprint of the steering wheel across the anterior chest.  The trachea is midline, and breath sounds are clear on the right but diminished on the left.  Neck veins are collapsed bilaterally.  Heart sounds are normal.  All four extremities are pale and cool to the touch.  There is no obvious external hemorrhage.  Portable chest x-ray shows multiple rib fractures, opacification of the left hemithorax, and a widened mediastinum.  ECG shows sinus tachycardia.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec25c8_d93e_534c_bc81_8f124bcbf549_MD0003_00 Patients who undergo rapid deceleration (eg, motor vehicle collision, fall >3 m [10 ft]) are at risk for blunt thoracic aortic injury (BTAI). Complete aortic rupture (ie, full-thickness tearing through intimal, medial, and adventitial layers) typically results in rapid exsanguination and death prior to hospital arrival. However, incomplete rupture (ie, adventitia still intact) may allow patients to survive long enough to receive medical attention. Likewise, patients with a complete rupture contained by a hematoma or surrounding tissues (as likely occurred in this patient) may survive the initial injury but require expedient evaluation and management to prevent rebleeding. They will likely be in hemorrhagic shock (hypotension, collapsed neck veins, pale and cool extremities). Although external signs of blunt chest trauma (eg, bruising, steering wheel imprint) are concerning for BTAI, there are no clinical findings specific for aortic injury. Chest x-ray findings suggestive of BTAI include a widened mediastinum, abnormal (eg, enlarged) aortic contour, and/or left-sided effusion due to hemothorax (which explains this patient's diminished breath sounds on the left). Concomitant injuries (eg, rib fractures) may be present. Diagnosis of BTAI can be confirmed via CT angiography for hemodynamically stable patients or transesophageal echocardiography (likely in the operating room) for unstable patients. Although hemodynamic support (eg, fluids, blood products) is indicated in hypotensive patients, systolic blood pressure is generally kept at <100 mm Hg to prevent injury extension and rebleeding while awaiting emergent operative repair. (Choices A and B) Bronchial rupture causes rapid air leakage from the tracheobronchial tree, manifesting on chest x-ray as pneumothorax, pneumomediastinum, and/or subcutaneous emphysema. Diaphragmatic rupture presents on chest x-ray with loss of diaphragmatic contour and/or presence of abdominal organs within the thoracic cavity. (Choice C) Chest x-ray findings of esophageal rupture may include widened mediastinum and pleural effusion (from accumulation of leaked esophageal contents). However, sudden-onset shock shortly after the insult makes BTAI much more likely. Mediastinitis from untreated esophageal rupture can result in septic shock but typically develops over hours to days (rather than minutes). (Choice D) Myocardial contusion can cause hypotension and tachycardia but is classically accompanied by arrhythmia or new bundle branch block. (Choice E) Myocardial rupture usually results in immediate death. Cardiac tamponade may result if the rupture is contained by the pericardium but would cause muffled heart sounds and distended neck veins. (Choice F) Motor vehicle collisions may cause traumatic spinal cord injury. Associated disruption of the sympathetic nervous system can lead to neurogenic shock and hypotension; however, bradycardia would be expected rather than tachycardia. Educational objective: Rapid deceleration can cause blunt thoracic aortic injury (BTAI). Widened mediastinum on chest x-ray should increase suspicion for BTAI and left-sided pleural effusion (hemothorax) may be present from hemorrhage preceding containment (eg, hematoma). Strict blood pressure control and emergent surgical intervention are necessary to prevent rebleeding and death. References: Blunt trauma of the aorta, current guidelines. (http://www.ncbi.nlm.nih.gov/pubmed/28683912) Vascular injuries after blunt chest trauma: diagnosis and management. (http://www.ncbi.nlm.nih.gov/pubmed/19751511)

A 44-Year-Old Man Is Brought to the Emergency Department After