Author: Russell Cross, MD
A trauma evaluation requires a complete and thorough examination beyond the ABCs of resuscitation. Secondary assessment includes careful examination of distal pulses. Absent lower extremity pulses could indicate aortic injury, vascular trauma from an adjacent fracture, or extremity compartment syndrome.
Patients with blunt aortic injury may show signs such as upper extremity hypertension, diminished femoral pulses ("pseudocoarctation"), and an intrascapular murmur. The presence of all three are distinctly uncommon, and diminished femoral pulses in a patientwith history ofblunt chest trauma or motor vehicle accident should always alert one to think of hidden aortic injury. Dissection should be suspected in any patient with a widened mediastinum on chest radiograph although a normal x-ray does not rule out an injury. Further imaging for dissection includes computed tomography scan or transesophageal echocardiogram.
Blunt aortic injury as part of blunt chest trauma, is responsible for 10% to 15% of motor vehicle-related deaths. It is a lethal injury that provides the surgeon with a small window of opportunity for effective surgical intervention. This window is often missed because the injury may be asymptomatic initially, followed later by catastrophic bleeding or other complications. In morethanhalfthecases,theinvolvedaorticsegmentistheproximaldescending aorta just distal to the origin of the left subclavian artery. Less common is involvement of the aortic arch, the distal thoracic aorta at the diaphragm, or multiple sites.
The classic mechanism of blunt aortic injury is sudden deceleration duringafrontal-impactmotorvehiclecollisionorafallfromheight;however, the possibility of blunt aortic injury should be considered in all victims of motor vehicle collision, regardless of the point of impact. The dominant pathophysiologic event in blunt aortic injury is sudden deceleration with creation of a shear force between a relatively mobile part of the thoracic aorta and an adjacent fixed segment. The three major points of fixation are the atrial attachments of the pulmonary veins and vena cava, the ligamentum arteriosum, and the diaphragm. The resulting tear may involve either part of the aortic wall or may be a full-thickness disruption that is contained by periadventitial and surrounding tissues.
Careful serial physical examination along with a high degree of clinical suspicion is needed to diagnose acute compartment syndrome. Absence of distal pulse along with pain out of proportion usually is diagnostic, although the presence of distal pulses cannot exclude the diagnosis of compartment syndrome.
Compartment syndromes in the lower extremity are often caused by open and closed fractures associated with arterial injury, gunshot wounds, extravasation at venous and arterial access sites, limb compression, burns, constrictive dressings, and tight casts. The rapid diagnosis and management of compartment syndrome is paramount to achieving a successful clinical outcome.
Thecommon causeofcompartmentsyndrome in anextremity is muscle edema, resulting from direct trauma to the extremity that causes an increase in compartment pressure, preventing venous outflow, causing backflow congestion, and worsening the cycle of increasing pressure and muscle ischemia. When there is a long bone fracture, the situation is exacerbated by fracture bleeding, which produces a space-occupying hematoma. Reducing the fracture increases the compartment pressures secondary to a decrease in the volume of the osseofascial space. External compressive casts or bandages further reduce the ability of the compartment to expand.
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center Trial of the American Association for the Surgery of Trauma. J Trauma. 1997;42:
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Mattox KL. Red River anthology. J Trauma. 1997;42:353–368.
Whitesides TE, Heckman MM. Acute compartment syndrome: update on diagnosis and treat
ment. J Am Acad Orthop Surg. 1996;4:209–218.
Read excerpts from these other book chapters related to Paraesthesia of the lower extremity:
Copyright Details: Avoiding Common Pediatric Errors, Copyright © 2008 Williams & Wilkins.
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More About This Book:
Title: Avoiding Common Pediatric Errors Authors: Anthony D Slonim MD, DrPH; Lisa Marcucci MD Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7489-6 
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