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The Speed of Sound: Don't Throw Out the FAST with the Bath Water

Butts, Christine, MD

doi: 10.1097/01.EEM.0000546137.87168.26
The Speed of Sound

Dr. Butts is the director of the division of emergency ultrasound and a clinical assistant professor of emergency medicine at Louisiana State University at New Orleans. Follow her on Twitter @EMNSpeedofSound, and read her past columns at http://bit.ly/EMN-SpeedofSound.

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An article published about a year ago cast serious doubt on the usefulness of the FAST exam in children—at least at first glance.

This University of California-Davis study randomly assigned patients to receive a standard trauma assessment or an assessment that included a FAST exam. Patients were included if they were under age 18 and had blunt torso trauma and stable vital signs. Examining physicians were asked to rate the suspicion of abdominal injury before and after the FAST and to state whether the FAST changed their decision to order a CT. They found no difference between the two groups in the rate of CT scans, missed abdominal injuries, length of ED stay, or hospital charges. (JAMA 2017;317[22]:2290; http://bit.ly/2NaVBYd.)

The study, which included 925 patients, seems to cast the FAST exam as the proverbial baby thrown out with the bath water, but there are some caveats. First, not only did they stick to stable patients, they excluded some of the sickest of these (patients with abdominal seat belt signs or GCS <9). Patients had an average Pediatric Trauma Score of 10 (scale from -6 to 12, with the higher number better). Only 50 of the patients had intra-abdominal injury, and only nine (slightly less than 1%) underwent laparotomy.

These kids weren't that sick, but almost half of them got CT scans anyway. Another interesting finding was that pre-scan suspicion of intra-abdominal injury did not change based on the results of the FAST. In the very low suspicion group, the patients mostly remained very low suspicion after ultrasound, and none was diagnosed with injury (including in the 28% who were still scanned). The time to CT was not significantly delayed in the FAST group.

Is FAST worth doing at all in stable pediatric patients if it did not make a difference in these categories? After all, one could argue the whole point of performing a FAST is to improve our diagnostic abilities, speed up our diagnosis, and decrease the number of CT scans (and the amount of radiation). Unfortunately, as pediatricians have been telling us for the longest time: Children aren't just little adults. We can't use the FAST the same way.

But does that mean it has no value in these patients? I would argue no. FAST can be another piece of the puzzle when viewed as an adjunct to other available data (exam, labs, vitals, our gestalt). It would have been nice to know with one of our recent initially stable pediatric patients, for example, that he had a large amount of abdominal free fluid before he decompensated in the CT scanner and was rushed to the OR.

My take? FAST has value when used in clinical context, but it isn't ready for prime time as a standalone in stable pediatric patients...yet.

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