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About to do a FAST ultrasound exam and not sure what to look for? Remember, a FAST exam, the acronym standing for Focused Assessment for Trauma, is simple but not simple-minded. A lot may be gained if you follow a disciplined, systematic approach. In fact more recently, the original FAST exam has been modified using a target organ approach called abdominal FAST or AFAST. Furthermore, a triple T designation for AFAST has been proposed and published since the exam may be used for trauma, triage, and tracking or monitoring. Our guest today is Dr. Greg Lisciandro who developed the AFAST target organ approach along with its abdominal fluid scoring system that helps predict the degree of intra-abdominal hemorrhage. He also developed the thoracic FAST or TFAST exam and most recently has added a third abbreviated technique called Vet BLUE standing for veterinary bedside lung ultrasound exam. Check out this podcast to learn all you need to know about FAST! Check out Dr. Lisciandro’s book from Wiley here!
By following the easily teachable wet lung versus dry lung elementary principle much is gained using the Vet BLUE pattern-based approach. Dry lung is characterized by the presence of a Glide Sign and A-lines (Glide Sign is called lung sliding in people). A-lines are horizontal air reverberation artifacts that extend from the primary white line identified by the Gator Sign orientation. The Gator Sign is imagined through the analogy of the rib heads as the eyes and the bright white line in between being the bridge of the nose as the alligator is partially submgerged below the water’s surface looking at you. The bridge of the nose is your point of focus as it represents the pulmonary-pleural line where, in the absence of pleural space disease, lung glides along the thoracic wall. The video clip of the one-eyed gator, by placing the rib head in the middle of the ultrasound field, is a trick that typically rapidly brings out the Glide Sign. The ultrasound beam is thrown in a much different direction with the reflective surface of the bone in the middle of the field and thus the Glide Sign is enhanced. The presence of the Glide Sign with A-lines is dry lung. A-lines without the Glide Sign represents pneumothorax. When unsure, look for the Lung Point (not covered here).
Once the Glide Sign is found at the higher/highest point on the thorax (chest tube site is the same as the Vet BLUE caudo-dorsal lung lobe region), pneumothorax has been ruled out. Now return to the two-eyed gator for at least a minimum of a single intercostal space (depth usually 4-6 cm) to count the number, if present, of ultrasound lung rockets (or B-lines). ULRs (or B-lines) represent forms interstitial edema and are created when small amounts of fluid are immediately next to air within the outer 1-3 millimeter of lung. ULRs are lung contusions in trauma or interstitial lung edema and its various forms in non-trauma. ULRs rapidly rule out pneumothorax at that site on the thoracic wall (just as does a Glide Sign and A-lines). ULR numbers correlates with degree of lung edema and severity of lung contusions. ULRs (or B-lines) are hyperechoic bright white streaks that extend from the lung surface through the far-field without fading and also swinging like a pendulum to and fro in concert with inspiration and expiration. Move through the remaining Vet BLUE sites for a pattern-based Vet BLUE approach for ruling in and ruling our forms of respiratory distress. For more information read the TFAST and Vet BLUE Chapter in the textbook Focused Ultrasound Techniques for the Small Animal Practitioner. For more information, please go to FastVet.com
FASTvet.com Copyright 2014 Dry Lung, A Lines with a Glide Sign
FASTvet.com Copyright 2014 Trick of the Trade, One eyed Gator for the Glide Sign
FASTvet.com Copyright 2014 Wet Lung, US Lung Rockets are hyperechoic streaks that do not fade and extend to the far field swing