TRAUMA / BLEEDING

Trauma US Pearls & Pitfalls

• Blood appears anechoic (black) when acute and free flowing, but hypoechoic (gray) when subacute or clotted. When it is gray it is much easier to miss, especially if you are not looking for it. Blood in the pericardial space that is related to trauma is gray in my experience (N=2. Go to the Ultrasound Library at www.EDinsight.com to see an image of this)
• The sensitivity of ultrasound in trauma improves with Trendelenberg positioning, repeat imaging and if you know how and where to look. For one, always look at the inferior tip of the liver, as it may be positive when Morrison’s pouch is not. Also, turn down the gain on the pelvic view if the bladder is full, otherwise the enhancement behind the bladder may “white out” a small pocket of fluid.
• If you cannot see the heart at all on the parasternal view, consider a small anterior left sided pneumothorax until proven otherwise. The chest film will not be sensitive enough. If the patient is going to the OR consider either going to chest CT first or placing an empiric chest tube if the patient remains unstable and must be rushed to surgery.
• If you work in a trauma center and don’t have an ED dedicated bedside ultrasound machine yet, you should. Get together with the trauma surgeons and request the hospital buy one and put on a course to train or re-train your doctors.

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TRAUMA ULTRASOUND IMAGES

 

Normal Morrison’s Pouch/RUQ

 

Normal LUQ

 

Normal Bladder

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RUQ View with Free Fluid (Image courtesy of Teresa Wu, MD)

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Behind the Bladder: Large Free Fluid

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Fluid in the pouch of Douglas (Gain too high)

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Blood within the urinary bladder from a GSW

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Fluid seen nowhere else but at the inferior anterior tip of the liver. Morrison’s view was negative on this patient.

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Non-traumatic effusions are more likely to be black than gray.

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Normal sub-xiphoid cardiac view.

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Fluid in the pouch of Douglas(transverse view)

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Small left Pneumothorax seen on CT but not seen on CXR. With ultrasound you won’t be able to find a window to the heart on the parasternal view, but will instead get “reverb” artifact.

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GSW Traumatic Tamponade: blood of intermediate density

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GSW Traumatic Tamponade: blood is often close to liver density

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Pearls and Pitfalls for Ultrasound Detection of a Hemothorax by Teresa Wu, MD

• The traditional four-view FAST exam can be expanded to evaluate the pleural space just cephalad to the bright hyperechoic hemidiaphragm.

• Because trauma patients are often lying supine strapped to a backboard in cervical spine precautions, portable chest radiographs may not detect small hemothoraces.  Bedside ultrasound can be used to quickly assess for the presence of a hemothorax, and is often better than chest radiography in detecting small amounts of pleural fluid (sensitivity 94.6-97% and specificity 99-100%).

• Use the curved array 2.5 to 3.5 MHz transducer or phased array transducer on most patients.  Lower frequency probes provide greater penetration in patient’s with an obese body habitus.

• Ensure consistent image directionality by orienting the external identification dot of the transducer towards the patient’s right or towards the patient’s head.  The indicator dot on the screen should be to the right of the ultrasound image.

• Position the probe in an oblique angle in the mid-axillary line between the 8^th and 11^th ribs.  Once you identify the hyperechoic bright white diaphragm, angle the ultrasound beam more cephalad to evaluate the pleural space just above the diaphragm.

• Normal lung tissue in the dependent areas of the thorax will share approximately the same echogenicity as a normal liver on ultrasound.  Free fluid in the pleural space will appear as a dark anechoic stripe just cephalad to the diaphragm.

• Observe the pleural space through a full respiratory cycle to monitor changes and characteristics of the fluid with diaphragm movement.  Use the sonographic images to help localize the ideal interspace for chest tube insertion.

• Remember that blood will appear less anechoic and more hypoechoic (gray rather than black) as it clots.  Don’t mistake clotting blood in the pleural space for normal lung tissue.  Scan cephalad above the clot to search for the more hyperechoic lung tissue floating within the hemothorax.  

 

Hemothorax - Image courtesy of Teresa Wu, MD

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