Soundings: The Rest is History (and Physical)

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Thoracic ultrasound can be life saving, but it shouldn’t be taken out of context

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As you walk into the room, EMS starts giving you the report. They have brought in a 75-year-old male who was riding his motorcycle in a residential area. Per report, he swerved to avoid a car backing out of a driveway and lost control of his bike. The patient skidded a few feet and was found 20 feet away from his bike. He has some chest pain and shortness of breath, but is otherwise asymptomatic. He was wearing his helmet and full leathers and had no loss of consciousness during the event. He meets your facility’s criteria for a trauma activation and has a pre-hospital 18 gauge peripheral IV in his right AC. EMS opted not to place him in cervical spine precautions because he had no head injury, no neck pain, and has no distracting complaints. His GCS was 15 in the field and he is not intoxicated. The patient’s most recent vital signs include a heart rate of 101 bpm, blood pressure of 176/92 mmHg, respiratory rate of 24, and oxygen saturation of 95% on 2L nasal cannula. His blood glucose level in the field was 120 mg/dL.

Your resident goes up to the head of the bed and starts the primary survey.

“Sir, what is your name?” “My name is Allen” the patient replies. “Airway intact!” your resident yells to everyone listening. As your resident listens to the patient’s breath sounds bilaterally and starts scanning his chest with the ultrasound machine at the bedside, you calmly walk over to the patient and lean over to tell him “Sir, there is going to be a lot of commotion around you right now as we work quickly to make sure you are OK after the accident. Don’t worry, we will take very good care of you…”

Before Allen can reply to your comment, your resident excitedly taps you on the shoulder and says, “Take a look at this! The ultrasound findings explain his chest pain and shortness of breath!” Your resident shows you the B-Mode ultrasound of the patient’s left lung at the 2nd to 3rd intercostal space, along the mid-clavicular line (Image 1). Neither of you note any lung sliding along the pleural line in real-time.

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Image 1: Ultrasound scan of the patient’s left chest in B-mode

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Image 2: Ultrasound scan of the patient’s left chest in M-mode

Your resident switches over to M-mode and you examine the findings together (Image 2).
What do you think of the ultrasound findings? Do you perform a chest tube thoracostomy? Scroll down for conclusion.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Both you and your resident reviewed the B-mode ultrasound of the patient’s lung and identified the bright white pleural line correctly. No lung sliding was noted in real-time along that pleural line. On the M-mode scan, the patient’s lung demonstrated a Barcode Sign as opposed to the Seashore Sign of a normal lung (pictured).

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Before your resident can call out to ask for a chest tube set up, you remind everyone that other etiologies can lead to an absence of lung sliding and a Barcode Sign on thoracic ultrasound. You ask everyone to pause, think, and reassess the patient. He is resting comfortably supine on the stretcher and his vital signs are starting to improve. He is not hypotensive or hemodynamically unstable at this time and therefore does not require emergent placement of a chest tube. Your resident picks up on some of your non-verbal cues and continues his primary and secondary survey in a very systematic manner. As the portable upright chest x-ray is being taken, your resident finishes up the trauma survey and begins to ask the patient more about the accident and his pertinent medical history.

In addition to a 40 pack/year smoking history, the patient also has known COPD and intermittently requires oxygen at home at baseline. His chest x-ray gets loaded up on the screen in the trauma bay, and you breathe a sigh of relief that the patient didn’t get an emergent and rushed chest tube based on the ultrasound findings alone. Most of the patient’s left upper chest is taken up by a large bulla visible on the chest x-ray. His lack of lung sliding and the Barcode sign on ultrasound were due to the parietal and visceral pleura being separated by this large and chronic bulla.

Given his symptoms, mechanism of injury, risk factors, and chest x-ray findings, the team decides to include a chest CT as part of the patient’s evaluation. Impressed by the age of the patient and the amount of pain he is in, the trauma team opts to admit him to observation so they can perform a tertiary survey and help get his pain under control.

As you walk out of the trauma bay, you think to yourself that sometimes things actually go pretty perfectly and the stars really can align. Too bad there’s not a metric that captures number of potential mistakes avoided and teachable moments brought to you by point-of-care ultrasound.

Pearls & Pitfalls for Performing Thoracic Ultrasound

  1. More and more health care practitioners are learning how to incorporate thoracic ultrasound into the evaluation and management of patients. Thoracic ultrasound is now being used to diagnose pneumothoraces, pneumonias, interstitial edema, masses, pleural effusions, empyemas, etc… Research is currently underway to evaluate the differences between ultrasound findings with pneumothoraces, blebs, and bullae.
  2. To perform a thorough thoracic ultrasound, utilize both a high frequency transducer to evaluate the superficial structures, and a lower frequency probe to scan through deeper structures.
  3. In normal patients, a thoracic ultrasound will demonstrate a hyperechoic pleural line just farfield between two hypoechoic rib shadows. The pleural line is made up of two layers: the parietal pleura overlying the visceral pleura.
  4. In real-time in B-mode, the visceral pleura can be seen gliding underneath the parietal pleura. The to-and-fro horizontal movement of the pleural line is called “lung sliding” on ultrasound.
  5. If there is air trapped between the parietal pleura and the visceral pleura, you will not be able to visualize lung sliding on B-mode ultrasound of the thorax. Similarly, if the visceral pleura is abutted against or adhered to the parietal pleura, lung sliding will also be absent on ultrasound.
  6. If you scan the pleura and underlying lung tissue in M-mode, you will see the characteristic Seashore Sign of normal lung. If the patient has air trapped in between the parietal pleura and visceral pleura (as in the case of a pneumothorax and some types of bullae), the artifact pattern you will see is called the Barcode Sign (Figure 3).
  7. Thoracic ultrasound is all about pattern recognition and understanding the ultrasound artifacts that arise from different interfaces within the thorax. Some of the artifacts and patterns noted can be caused by various etiologies and diagnoses. For example, bullae and blebs can appear similar to a pneumothorax on ultrasound. It is important to use ultrasound in conjunction with your history and clinical findings to assist in the diagnosis and management of patients presenting with cardiopulmonary complaints.
  8. Practice, Practice, Practice: The best way to minimize errors is through experience, so scan lots of normal anatomy. The more scans you do, the better you will be able to differentiate abnormal from normal, even when you may not be sure exactly what the abnormality is. An image library of normal and abnormal scans helps immensely, so check out the Soundings library on EPMonthly.com.

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