The focused abdominal sonography for trauma examination can reliably identify patients with significant intra-abdominal hemorrhage in life-threatening pelvic fractures
J Trauma Acute Care Surgery June 2018 - Pubmed Link
Take Home Points
1. The FAST is sensitive and specific for intraperitoneal blood in the unstable pelvic fracture patient.
2. In this population, it's a neat idea that the FAST has the potential to help inform the decision between going to OR, going to IR, or placing REBOA, but this study does not provide significant evidence for this strategy.
Background
The FAST exam has been used in trauma a long time, but oh the times they are a’ changin. A lot has happened since the FAST was incorporated into many trauma protocols. Now everybody gets a pan-SCAN and there are more fun procedures that can be done to help with hemorrhage. Resuscitative endovascular balloon occlusion of the aorta (REBOA) is one of these newer therapies. By percutaneously placing an endovascular balloon, the aorta can be blocked for long enough to control life threatening bleeding. This is still a relatively new technique for non-compressible hemorrhage, but there have been some promising work done. These authors posit that since pelvic fractures with severe bleeding may be best managed by REBOA, perhaps ultrasound can help determine when this would be indicated. They are taking a little bit of a leap here since REBOA is not actually used in their study but the idea is that if there is no intraperitoneal blood perhaps the patient needs something besides a laparotomy. Regardless, they note that traditionally the FAST is not great for hemorrhage in the setting of pelvic fracture (26% sensitive!), so it makes sense to find out how well it works in a sick hemorrhaging population.
Question
Can the FAST exam detect clinically significant intraabdominal hemorrhage in complex pelvic fractures?
Population
Single Level 1 trauma center
Patients who met inclusion between 2005-2015
Inclusion:
- Pelvic fracture + preperitoneal pelvic packing (PPP)
Exclusion
Imaging at outside hospital
No FAST recorded in the ED
Operative intervention at outside hospital
Design
Retrospective
Looking at patients with pelvic fractures and comparing FAST determination of intraperitoneal free fluid to evidence of hemorrhage on CT or laparotomy
Collected demographics, imaging studies, and operative interventions
Their protocol was that all patients (presumably with suspected pelvic fractures) who had SBP <90 mmHg after 2 units PRBC → received PPP and external fixation
FAST considered positive if any intraabdominal free fluid as interpreted by the bedside clinician. FAST also considered positive if any view was indeterminant.
Also routinely repeated the FAST exam. This is important because if the first FAST was negative but second one showed free fluid, the first FAST was not counted as a false negative.
FAST considered true positive if intraabdominal hemorrhage on laparotomy or seen on CT. True negative FAST meant no blood on CT or did not require intervention.
Who did the ultrasounds?
Trauma surgeons or ultrasound fellowship-trained ED faculty
The Scan
Curvilinear (or phased array)
The FAST Exam - for this article they did the standard 4 views (RUQ, LUQ, pelvic, pericardial)
Results
Over the 10.5 years of the review, 2,246 patients admitted with pelvic fractures - 132 (6%) in refractory shock underwent PPP. 51 excluded (mostly because they had outside hospital imaging)
N = 81
Patients
Mean age 45 yo
Mean Injury severity score 50
All blunt trauma injuries, mostly MVC
Mean PRBC in ED 3 units
Mean lowest SBP 72
Mean highest HR 116
There were 28 FAST positive patients (34.6%), 26 confirmed (so 2 false positives).
Primary Outcome
Accuracy of FAST exam Compared to CT or Laparotomy for Diagnosis of Hemorrhage
Sensitivity 96%
Specificity 96%
2% False negative, 7% false positive
Additional Findings
53 patients had negative fast, 52 patients had negative CT and laparotomy
False positives (2) - one had +pelvic FAST view, CT showed pelvic space hematoma (but no intraperitoneal blood). Second had +RUQ, no hemoperitoneum on laparotomy (just mesenteric hematoma)
False negative (1) - There was one patient with negative FAST that had only palpable carotid pulse (no blood pressure recorded), had negative FAST went to OR, underwent PPP, laparotomy, splenectomy, liver packing.
There were also 4 "maybe could have been" False negatives. In these patients there were positive findings after a negative FAST, but it seems they did not count these as False negatives because there was no intervention.
Grade II liver laceration with hemoperitoneum managed non-operatively
Grade III liver injury managed non-operatively
Scant blood without evidence of intraabdominal injury found on laparotomy
Grade II splenic injury with 250 mL of blood in abdomen, splenectomy not required
Limitations
Single center study with a very specific pelvic fracture protocol. The ultrasound users were likely highly trained (trauma surgeons and ultrasound fellowship trained emergency physicians), so accuracy may not be as good in more novice population of operators.
Retrospective. FAST images could not be reviewed, operative and CT findings based on documentation alone. A lot could have changed over 10 years.
Very small population of overall pelvic fractures because only included those that underwent PPP. These people were very sick, had high incidence of injury, so FAST may not perform as well in different population.
How many of the positive FAST exams were caught only on the repeat FAST? If that is not part of the protocol for other place, may not have this accuracy. Additionally, their definition of positive and negative would lend itself to a higher accuracy. We know that the FAST is more specific than sensitive. They improve sensitivity by counting indeterminate scans as positive. In addition, they allowed positive studies to be positive only on imaging, but for negative studies, they required an operative intervention even if there were imaging findings.
Discussion
Where were the FAST scans positive? That would have been interesting to see in pelvic fractures. This study seems to follow previous literature that the FAST works best (and was in fact designed for) the unstable patient.
Authors state that since FAST can accurately identify the need for laparotomy, if the FAST is negative but the patient is hemodynamically unstable → might be an indication for REBOA to control the pelvic fracture related bleeding. Would this have panned out well in their cohort? They mention that of the patients with negative FASTs, there was only one that required an intervention on laparotomy. It's an interesting idea, but its way to early to implement this idea. We are barely figuring out the right population who benefits from REBOA. Once we establish that, then we can determine whether ultrasound can help in identifying these patients.
Take Home Points
1. The FAST is sensitive and specific for intraperitoneal blood in the unstable pelvic fracture patient.
2. In this population, it's a neat idea that the FAST has the potential to help inform the decision between going to OR, going to IR, or placing REBOA, but this study does not provide significant evidence for this strategy.
Our score
Expert Reviewer for this Post
Casey Wilson, MD, RDMS @CaseLWilson
Emergency Ultrasound Director and Fellowship Director at Grand Strand Medical Center in Myrtle Beach, SC, an affiliate of USC
Reviewer's Comments
Another win for the FAST, hopefully some of our savvy trauma centers routinely placing REBOA in their hemodynamically unstable and peri-arrest patients will generate some further data in support of this. Bottom line – do the study, repeat it, and be aware of its shortcomings.