Approach to the Mediastinum in Trauma: Density vs. Width Tammy Washut MS4

Traumatic Injuries to Worry About Mediastinal hematoma Aorta/great vessel injury Spinal hematoma

Mechanism Rapid deceleration injury Blunt chest trauma- MVA, falls The sudden stop causes the blood filled descending aorta to “snap”. The aortic arch is fixed in position by branches from the arch. Mechanism Rapid deceleration injury Blunt chest trauma- MVA, falls Sudden deceleration as sternum hits steering wheel. As the aortic tube “snaps”, the intima is torn just distal to left sub- clavian artery.

External signs “Seat belt sign” Chest ecchymosis Sternal/Rib fractures

Chest X-ray Classically taught to look for widened mediastinum Wide mediastinum = 8 cm What is the problem with this??? Wide mediastinum has a broader differential than paratracheal density

Causes of Wide Mediastinum Magnification Rotation Mediastinal hematoma Spinal hematoma Lymphadenopathy Long intravascular volume Obese patients

Magnification

Magnification Film placed directly behind the patient Initially used to determine the 8 cm criteria for wide mediastinum

Magnification Film placed under the backboard 17% enlargement

Magnification Film placed in trauma bed 25% enlargement

Rotation 4 cm 7 cm Rotated Right Rotated Left For example, when the patient is rotated to the right, the mediastinum is artificially widened by laterally displacing the SVC and aorta. When rotated to the left, the mediastinum is artifically narrrowed by overlapping the SVC and aorta. Rotated Right Rotated Left

Intravascular Volume 7 cm 4 cm Pre-Dialysis Post-Dialysis Intravascular volume status can also affect the width of the mediastinum as shown in this dialysis patient pre and post dialysis Pre-Dialysis Post-Dialysis

Lymphadenopathy Lymphadenopathy can widen the mediastinum as demonstrated in this patient with sarcoidosis

Right Paratracheal Density Composed of azygous vein and SVC Density normally less than aortic arch Increased = hematoma Why? Not affected by technical factors Simple Right paratracheal region composed of the azygos vein and SVC --Right paratracheal region should be less dense than the aortic arch --As density of right paratracheal region equals or exceeds that of the aortic arch – increased suspicion for mediastinal hematoma --This sign is different than the previously published signs as…Density is not affected as much by technical factors and we felt it was a simple and reproducible sign

Right Paratracheal Density This example demonstrates what the right paratracheal region looks like in a patient with a normal PT density and in a patient with increased PT density and proven mediastinal hematoma… Normal Increased Density

Mediastinal Hematoma Other Signs: PT stripe Apical cap Aortic Arch NG deviation Tracheal deviation --Additional signs that have been utilized for detection of mediastinal hematoma include…all of which are present in this patient…

Mediastinal Hematoma Other Signs: PT stripe Apical cap Aortic Arch NG deviation Tracheal deviation

Mediastinal Hematoma Other Signs: PT stripe Apical cap Aortic Arch NG deviation Tracheal deviation

Mediastinal Hematoma Other Signs: PT stripe Apical cap Aortic Arch NG deviation Tracheal deviation

Mediastinal Hematoma Other Signs: PT stripe Apical cap Aortic Arch NG deviation Tracheal deviation

OHSU DATA Hypothesis: Right paratracheal density is discriminatory sign in trauma patients with widened mediastinum So, our hypothesis was that the R PT density is a discriminatory sign for the presence of mediastinal hematoma in trauma patients with widened mediastinum…

Methods 122 Trauma patients (2001-2003) Screening Trauma chest radiograph Mediastinal width > 8.0 cm CT Chest w/contrast within 24 hours Four readers of different levels of training R paratracheal region evaluated We evaluated 122 trauma patients presenting to OHSU ED from 2001 to 2003 whom underwent screening chest radiograph, found to have a mediastinal width > 8.0 cm and whom underwent CT chest within 24 hours of presentation… --Four readers of different training levels evaluated the R PT density as being normal or increased (defined as equal or greater than density of aortic arch)

Methods Patients categorized by ISS AIS by body region Chest: 1-6 Low risk: 0-2 (80 patients) High risk: >2 (42 patients) Patients were divided into low and high risk categories based on their Chest ISS

Results 19 mediastinal hematomas (15.6%) 5 aortic injuries (4.1%) 13 high-risk 6 low-risk 5 aortic injuries (4.1%) 4 deceased (3.3%) There were…

Results

Results

Results

Results Interestingly, the mediastinal width was greater in those without hematoma than those with, again demonstrating the inconsistency of this commonly used sign…

Results The overall average of all 4 readers seen herre demonstrates very high sensitivity, NPV, and quite high specificity in the low-risk population

Results Compared to the other commonly used signs for detecting mediastinal hematoma, the sensitivity of the R PT density sign is significantly better Sensitivity

Limitations Single institution Presented to readers in artificial setting Relatively few hematomas AIS/ISS scoring not useful as triage tool

Strengths Trauma patients with widened mediastinum Confirmed by CT w/in 24 hours Blinded analysis Clinical information available on all patients

Conclusions Screening chest radiograph valuable in low/moderate risk trauma patients Right paratracheal density valuable Avoid CT in low-risk patients 7.3% normal mediastinum High risk patients should have CT --It is important to remember, however, that many high risk chest trauma patients will have a normal mediastinum on chest radiograph and therefore, high risk patients should have CT regardless of the chest radiograph findings

Recommendations Low risk patients with or without a wide mediastinum but no paratracheal density do not need to have CT of the chest High risk patients with mechanism of injury (i.e. seatbelt sign) should go to CT regardless Paratracheal density, not width, should direct further management

Examples

Possible Hematoma? Yes- aortic rupture Paratracheal density on right and loss of aortic arch definition

Possible Hematoma? Yes, but in this case it is lymphadenopathy in a high risk trauma patient This patient should get a chest CT

Possible Hematoma? No- mediastinum is wide, but no paratracheal density Patient is rotated to right

Examples

Examples

Examples

References Melton SM et al., J Trauma 2004; 56:243-250 Mirvis SE et al., Radiology 1987; 13:487-493 Baker SP et al., J Trauma 1974; 14:187-196 Woodring JH et al., Radiology 1984; 151:15-21 Parmley LF et al., Circulation 1953; 17:1086-1101 Woodring JH et al., J Emerg Med 1990; 8:467-476 Woodring D et al., Ann Thor Surg 1984; 37:171-178 Blackmore CC et al., Emerg Radiology 2000; 7:142-148 Patel NH et al., Radiology 1998; 209:335-348 Milne EN et al., Radiology 1984; 153:25-31 Demetriades D et al., Arch Surg 1998; 133:1084-1088 O’Connor CE et al., Emerg Med J 2004; 21:414-419 Special thanks to Dr. Marc Gosselin and Dr Peter Verhey for references, images and study data and slides.