CHICAGO – The bedside focused assessment with sonography for trauma exam is used infrequently in children with blunt abdominal trauma.
When the FAST exam was used in children with a low to moderate risk of intra-abdominal injury (IAI), however, there was a substantial reduction in subsequent abdominal CT use, a planned subanalysis of a large prospective, observational trial showed.
Patrice Wendling/IMNG Medical Media
Dr. James Holmes
Although the FAST exam was shown to safely decrease abdominal CT use in two randomized trials in adults, its use in children who have blunt abdominal trauma is controversial, Dr. James Holmes observed at the annual meeting of the Society for Academic Emergency Medicine.
"One of the concerns is that ultrasound is not 100% sensitive," he said. "Depending on what study you look at, it’s about 60%-70% for all intra-abdominal injuries and 80%-90% for fluid. So there’s the risk that – if you have a negative ultrasound – that child could still have an intra-abdominal injury." However, he added, "we had no patients that had a negative ultrasound that subsequently had a missed injury."
The 20-center prospective study enrolled children younger than 18 years (median, 10.7 years) with blunt abdominal trauma and a Glasgow Coma Scale score greater than 8. Children were excluded from the analysis if they went directly from the emergency department to the operating suite prior to CT, had age-adjusted hypotension, or came from one of eight centers performing FAST exams on fewer than 5% of patients.
In all, 6,558 patients were eligible, 3,076 (47%) underwent abdominal CT, 381 (5.8%) were diagnosed with IAI, and 887 (13.5%) underwent the FAST exam.
Although FAST was not used that often, the variability among sites was quite impressive, with some centers just barely above the cutoff at 5.5% and others using the exam in 58% of eligible patients, said Dr. Holmes, professor of emergency medicine at University of California Davis Health System in Sacramento.
Notably, use of the FAST exam increased as clinician suspicion for IAI increased: 11% in patients with a less-than-1% (very low) risk of IAI, 13.5% with a low (1%-5%) risk, 20.5% with a moderate (6%-10%) risk, 23.2% with a high (11%-50%) risk, and 30.7% with a very high (greater than 50%) risk.
Overall CT rates were 22.2%, 67%, 89.7%, 95%, and 97.2%, respectively.
Relative risk calculations for CT use stratified by clinician suspicion of IAI showed that patients with low or moderate risk of IAI were less likely to undergo CT scans following a FAST exam than were those who did not have the exam, Dr. Holmes said. The CT rate with a FAST exam was 55.2% vs. 68% without the exam among low-risk patients (relative risk, 0.81) and 80% vs. 92.4% among moderate-risk patients (RR, 0.85).
"That’s a substantial reduction in CT use in those populations," he noted.
No difference was seen when the FAST exam was performed in children at high risk (RR, 0.99) or very high risk (RR, 0.97) of IAI because they essentially all went on to CT. Similarly, those at very low risk of IAI derived little benefit from the exam (RR, 0.97), probably because the vast majority of these patients don’t undergo CT scans, he said.
During a discussion of the results, Dr. Holmes said the observation that FAST use decreases CT scans in low- to moderate-risk patients makes sense because the FAST exam has a reported negative likelihood ratio of 0.2 in children.
"If you have someone who has a 5% risk, once you apply that ultrasound to that patient and a likelihood ratio of 0.2, it decreases their risk substantially such that they’re at really low risk of having an intra-abdominal injury," he said. "We think the sweet spot is that group around 5%, based upon that prior literature that showed a negative likelihood ratio of 0.2."
According to the researchers, led by Dr. Jay Menaker of the University of Maryland Medical Center in Baltimore, a randomized, controlled trial is required to determine the benefits and drawbacks of the FAST exam in the evaluation of pediatric blunt trauma.
Dr. Holmes said they are already in the process of a single-site trial using 1:1 block randomization to the FAST exam after initial history and physical examination or to no FAST exam, with patients followed through their hospital course, if admitted, or contacted by telephone 1 week later, if discharged from the ED. Outcomes will include CT rates, length of stay in the ED, missed intra-abdominal injury, or delayed diagnosis of IAI.
This work was supported by the Centers for Disease Control and Prevention and the Emergency Medical Services for Children Program.