Soundings: Traumatic hypoxia

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It’s just another typical Saturday night in the ED. You’ve just finished stabilizing a biker who ran his motorcycle into a tree sans helmet, the two intoxicated teenagers who tried jumping from the roof into their backyard swimming pool, and the 80-year-old gentleman with CHF who thought chicken pot pies were a reasonable part of his low salt diet.


Your charge nurse grabs you to give you a “heads-up” on a multi-vehicle collision that just transpired on the interstate.  Six of the ten victims are en route to your facility and all six sound sick.

The trauma team has already been alerted and within minutes its members are masked and gowned in your trauma bay waiting for the victims of the accident. You grab your senior EM resident, your trusty ultrasound machine, and smile at the notion that traumas still give you a little rush of endorphins after all these years. Within minutes, EMS is rolling in with the first of your six MVC
patients and, like a well-orchestrated dance, the “running” of the traumas commences. All six require emergent intubations to protect their airways, and two are receiving bilateral chest tubes for pulseless electrical activity.  The patient your resident is managing, who seemed quasi-stable to start with, suddenly starts dropping her O2 sats and her blood pressure. The respiratory therapist takes her
off the vent and starts bagging her manually, while your nurses crank up the Level 1 infuser. The patient’s O2 sats are hovering around 90% as your senior resident calls for a STAT chest X-ray and reaches for two 14-gauge needles for bilateral needle decompression. Before your resident can
pop the lid off the Betadine bottle, you’ve already scanned the patient’s left hemithorax and clearly identified signs like lung-sliding and comet tails that lead you to believe that a pneumothorax is not present on that side (Stay tuned for future articles on Ultrasound Detection of Pneumothoraces). Sweeping your ultrasound probe in an oblique angle at the level of T10 on the left side gives you
the image below (left).
You quickly scan the right hemithorax and see the second image (right). What important finding does the second image reveal? What should be the immediate treatment? Should you wait for chest X-ray results in this patient?
See next page for diagnosis and discussion
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The first image (top) demonstrates normal findings on the left. The second image (bottom) demonstrates a large right-sided hemothorax, which should be immediately drained. If the patient were stable, it would be reasonable to wait for the chest X-ray to come back, but since she is not, immediate chest tube thoracostomy is indicated.  Instead of slamming two largebore IV’s into both of the patient’s lungs, your resident wisely calls out for a chest tube set-up and begins prepping the right
chest wall. As your resident finishes securing the chest tube to the Pleurovac, the radiology tech has finally made his way through your other “STAT” Xrays and is finally ready to shoot the chest X-ray that was called for when your patient first started becoming hypoxic. The trauma attending peaks his head in to order for autotransfusion of the 700 mL of blood that your resident just drained from the patient’s pleural space, and informs the rest of the team that Scanner 1 is ready for this patient. You’re just about to start disinfecting the ultrasound probe in your hand as you hear overhead that you are needed for a cardiac arrest that has just arrived in Room 1. Yes, just another typical Saturday night in the ED. 

Pearls & Pitfalls for ultrasound detection of a hemothorax

  • 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 >>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 between the 8th and 11th ribs. Once you identify the hyperechoic bright white diaphragm, angle the ultrasound beam more cephalad to evaluate the pleural space just above the diaphragm.

Brady Pregerson, MD, oversees QI for ED Ultrasound at Cedars-Sinai Medical Center in Los Angeles. Check out more from Dr. Pregerson at Teresa Wu, MD, a clinical assistant professor in EM at Florida State University, completed her ultrasound fellowship at Stanford University Medical Center.


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