The FAST exam (Focused Assessment with Sonography in Trauma) has been utilized to evaluate adult patients with blunt and penetrating trauma for more than 20 years. Some controversy still exists, but ultrasound has been incorporated into the evaluation and accepted as part of the Advanced Trauma Life Support (ATLS) algorithm. The case is not so clear, however, for pediatric trauma.
Does the FAST exam have a place in evaluating pediatric patients? Can it be used to decrease the number of CT scans performed? Can any conclusions be drawn from a positive or negative scan in a hemodynamically stable patient?
A recent case series highlights the essential dilemma in dealing with pediatric patients. (J Emerg Med 2016;50:753.) Unlike adult patients in whom the presence of free intraperitoneal fluid following trauma is frequently associated with the presence of an injury, children can (and often do) exhibit free fluid without any discernible injury. The authors describe five cases in which pediatric blunt trauma patients were identified as having positive FAST exams.
All of these patients were hemodynamically stable, had normal mental status, and none had concerning abdominal exams. Some of these patients had CT scans at the discretion of the examining physician, and some were simply observed. None of these scans revealed intra-abdominal injury, and none of the patients managed with serial abdominal exams needed any further treatment. The authors of the study raise an excellent question about the meaning of a positive FAST in a pediatric patient: What does it indicate about possible underlying injury, if anything?
A review of the literature regarding FAST in pediatric patients yields a wide range of opinions. Multiple attempts have been made to use the combination of the FAST exam with other factors (AST/ALT values, other historical or physical exam findings) to delineate better which patients may be able to avoid CT scanning. Significant controversy still exists, most likely because of the lower sensitivity of the FAST exam in pediatric patients, even in the best of hands.
The findings of this mountain of research probably should not be considered surprising, particularly if FAST is viewed as it should be: an extension of a physician's physical exam and clinical judgment. The patients in this case series were described as low risk for intra-abdominal injury. Some had suffered trauma to the abdomen and torso, but none of them had significant tenderness on exam, and all were alert and cooperative. How many of us would have ordered an abdominal CT scan for these patients?
On the other end of the spectrum, pediatric abdominal injuries are notorious for presenting without significant free fluid. How many of us faced with a hemodynamically stable patient with significant mechanism and abdominal tenderness would be reassured enough by a negative FAST exam to avoid a CT?
It seems that when it comes to FAST in the pediatric patient, the real question is not what does it mean, but should we be doing it at all in the stable patient?
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