|Abdominal trauma; Ultrasonography; Emergency
severity index; Hemoperitoneum
|In the United States, trauma accounts for 37 million emergency
room visits annually and is the leading cause of death in persons
younger than 45 years old . Five million cases of blunt abdominal
trauma (BAT) occur each year, and 50,000 deaths occur annually
because of blunt injury . Early recognition of severe abdominal
injury is paramount, as the rapid identification of hemoperitoneum
expedites patient care to the operating room for exploratory laparotomy
and definitive management. The traditional diagnostic tool for
identification of hemoperitoneum has been the diagnostic peritoneal
lavage (DPL). Over the last 30 years, bedside ultrasound has been used
with increasing frequency to assess for intra-peritoneal hemorrhage
[3-7]. Focused Assessment with Sonography for Trauma (FAST)
utilizes clinician-performed ultrasonography at the patient’s bedside to
rapidly identify the presence of hemoperitoneum or hemopericardium
associated with acute life threatening injuries. Current literature has
demonstrated improved outcomes and shortened time to operative
intervention when this examination is performed by trained personnel
and included in the initial evaluation of the unstable trauma patient
[8,9]. Point of care ultrasound (POCUS) is defined as a focused, goaloriented
bedside ultrasound examination performed by the treating
physician to answer a specific question or guide an invasive procedure.
POCUS is performed by physicians of various specialties such as
emergency medicine, intensive care, and various surgical specialties.
The archetypal POCUS examination, the FAST, was initially developed
by emergency physicians (EP) and surgeons caring for traumatically injured patients, and over the past 20 years the number of applications
a nd types of specialists using bedside ultrasound has grown [10,11].
On August 1st 2012, Harborview Medical Center, a large inner-city
hospital and training site for the University of Washington, formally
incorporated EP-performed FAST exams for the initial evaluation
of severely injured BAT patients. Prior to this date, unstable BAT
patients received either a FAST exam or a DPL as the initial diagnostic
evaluation for hemo-peritoneum. The FAST exam was performed
either by a radiologist or emergency physician and interpreted in real
time by the performing physician, while the DPL was performed by
a general surgeon. After the protocol change, the FAST exam became
the first method of investigation, with the DPL reserved for patients
with a negative FAST and ongoing hemodynamic instability. We sought
to evaluate the accuracy of EP FAST exams for unstable BAT patients.
Secondary analysis included determination of the trends in use for DPL
for unstable BAT patients.
|We conducted a retrospective analysis of all Emergency Severity
Index (ESI) level 1 trauma patients at Haroborview Medical Center
using the Emergency Department electronic tracking system over a
26-month period (July 1, 2011 to August 31, 2013), thirteen months
before and after the protocol change. Patient inclusion criteria were:
blunt thoracoabdominal injury, full trauma team activation, and a FAST
examination performed as part of the initial diagnostic evaluation. The
criterion for full trauma team activation is hemodynamic instability, as
demonstrated by hypotension (systolic blood pressure <90 mm Hg),
need for cardiopulmonary resuscitation, obvious major vascular injury
or need for ongoing transfusion of blood products to maintain blood
pressure, as determined by the trauma team. Patients with penetrating
injury, no FAST exam, no confirmatory computed tomography (CT)
or laparotomy, or who were transferred from an outside hospital with
CT imaging of the abdomen already performed, were excluded from
analysis. Data was collected using a closed-ended abstraction form for
demographics, results of the FAST exam, peritoneal fluid aspirate or
lavage, CT, and operative findings when available. FAST exam results
were noted to be positive, negative, or indeterminate per the medical
record. Indeterminate FAST exams were excluded from determining
test characteristics. DPL results were positive if there were greater than
100,000 cells/mm3 red blood cells, 500 white blood cells/mm, elevated
amylase, bile or the presence of fibrous material. The primary endpoint
was the presence of any amount of intra-peritoneal hemorrhage on
CT, or intra-peritoneal hemorrhage identified in the operating room.
Inter- rater reliability was determined by comparing FAST results to
CT or laparotomy findings using a weighted kappa score. The study was
approved by the University of Washington institutional review board.
|Haroborview Medical Center is the only designated level 1 trauma
center in a five-state region in the Pacific Northwest that includes
Washington, Wyoming, Idaho, Alaska, and Montana, with an annual
Emergency Department census of over 75,000 patients per year. It
serves as the regional referral hospital for a large portion of the Pacific
Northwest, and is the primary training site for physicians of various
specialties including radiology, trauma surgery and emergency
|A total of 667 ESI level 1 BAT patients were identified using
the ED electronic tracking system (Figure 1). 249 patients had full
trauma activation, and 185 (74%) unstable BAT patients had a FAST
examination performed as part of their initial evaluation with a
confirmatory test for comparison. A total of 71/185 (38%) patients also
had DPL performed in conjunction with the FAST exam to identify
or confirm hemoperitoneum in critically unstable BAT patients. Most
patients had full trauma team activation for hypotension and were
injured in a motor vehicle collision (Table 1).
|Emergency physician FAST
|90 FAST examinations were performed by EPs for unstable BAT
patients in whom a confirmatory CT or operative report was available.
There were 23/90 positive, 53/90 negative, and 13/90 indeterminate
EP FAST exams. There were 22 true positive, 46 true negative, 1 false
positive, and 7 false negative examinations for a sensitivity, specificity
and accuracy of 76% (95% CI 56 to 89 %), 98% (95% CI 87 to 99 %), and
89% for any amount of free intra-peritoneal hemorrhage (Table 2). The one false positive EP FAST had a normal DPL, no CT findings of intraperitoneal
hemorrhage, and did not require operative management.
Of the seven false negative exams, four had trace or small amounts of
intra-peritoneal hemorrhage. Three had moderate to large amounts of
hemorrhage found on laparotomy, two of which were post-angiography
with embolization (Table 3). 6/7 false negatives had associated pelvic
fractures. Excluding cases of trace or small fluid collections would
have increased the EP FAST sensitivity to 88% (95% CI 67 to 96 %).
Of the indeterminate FAST exams, one case was notable for moderate
amount of hemo-peritoneum diagnosed by CT not requiring operative
management. All other indeterminate EP FAST exams had no intraperitoneal
|Of the 95 FAST exams performed by the Department of Radiology,
there were 12 positive, 68 negative, and 16 indeterminate examinations.
There were 11 true positive, 63 true negative, 1 false positive, and 5
false negative FAST exams for a sensitivity, specificity and accuracy of
69% (95% CI 41 to 87 %), 98% (95% CI 90 to 99 %), and 93% for any
amount of free intra-peritoneal hemorrhage (Table 4). The lone false
positive case was followed by a negative DPL, a CT without evidence
of free intra-peritoneal hemorrhage and no operative management.
All 5 false negative exams were associated with trace or small amount
of hemorrhage, and none required an exploratory laparotomy. 3/5
false negative Radiology FAST exams were associated with pelvic
fractures, and two required angiography guided embolization (Table 5).
Excluding cases of trace or small hemorrhage would have increased the
sensitivity of the radiology FAST exam to 100%. Of the indeterminate
Radiology FAST examinations, four were ultimately positive for
internal hemorrhage, three of which had moderate to large amounts of
blood on laparotomy.
|Accuracy of FAST
|Of the 185 FAST exams performed collectively, there were 33 true
positive, 109 true negative, 2 false positive, 12 false negative, and 29
indeterminate FAST examinations. The sensitivity, specificity and
accuracy were 73% (95% CI 57 to 84%), 98% (95% CI 93 to 99%), and
91% respectively. Inter-rater reliability between two study investigators
(AA and BB) was good (κ=0.78). Test characteristics for hemodynamically
unstable BAT patients with moderate to large amounts of
hemo-peritoneum, were sensitivity 92%, specificity 98%, and accuracy
97%. The difference in sensitivity between EP FAST exam (76% [95% CI
56 to 89 %]) and Radiology FAST exam (69% [95% CI 41 to 87 %]) was
statistically insignificant (p=0.7284), and both exams had near identical
accuracy rates (89% v 93%) making neither exam better or worse than
|Diagnostic peritoneal lavage
|A total of 71 patients underwent a diagnostic peritoneal lavage to
evaluate for hemoperitoneum. Of the 71 DPLs performed, 53 (75%)
were performed after a negative FAST, 15 (21%) after an indeterminate
FAST, and 3 (4%) after a positive FAST exam. Five patients had grossly
positive peritoneal aspirates, four of which had a final operative
diagnosis of traumatic hemoperitoneum. 34 DPLs were performed in
79 BAT patients before the new protocol and 38 DPLs were performed
in 106 patients after the protocol change. While the overall use of DPL
in critically injured BAT patients decreased with the implementation of
the new protocol, this trend was not statistically significant (p=0.17).
|One challenge of trauma care is the rapid identification of significant abdominal injuries in hemodynamically unstable patients.
Highly accurate, the FAST exam is also repeatable, noninvasive, easily
learned and can be performed at the bedside, and thus plays a vital
role in the evaluation of trauma patients [12-15]. While computed
tomography is the gold standard for diagnosing solid organ injury, the
FAST exam is associated with expedited care in BAT, shorter hospital
stay, and lower overall cost of care [16-18]. The FAST exam has the
potential to mobilize resources quickly for critically injured patients,
rapidly identifying those who would benefit from laparotomy
|Our findings demonstrate that EP FAST exams in unstable BAT
patients had a sensitivity, specificity and overall accuracy of 76%, 98%,
and 89% for any amount of free intra-peritoneal hemorrhage. The
sensitivity for FAST examinations in our study was somewhat lower
than previously reported because our study was designed, a priori,
to determine test characteristics for any amount of free hemorrhage,
regardless of its clinical significance. It is generally appreciated that
the sensitivity of the FAST exam is highest for hemodynamically
unstable patients with moderate to large amounts of intra-peritoneal
hemorrhage. The FAST exam is limited in its ability to detect trace and small amounts of hemorrhage 18. With this in mind, EP FAST
exams in our study would have demonstrated a sensitivity, specificity
and accuracy of 88%, 98%, and 94% respectively for moderate to
large amounts of blood in unstable BAT patients, results comparable
to published findings in similar patients [19-24]. We did not find a
significant difference in test characteristics for FAST performed by
Radiology versus EPs.
|The main limitations to our study were small sample size, single
center, and retrospective design. Because we searched for ESI level 1
trauma patients only, patients initially triaged at a lower acuity level,
yet subsequently became unstable, were not identified, and could not
be included in this study. Patients with indeterminate FAST exams,
no documented FAST exam results, or without confirmatory findings
were not included in the analysis, all of which could have significantly
changed accuracy rates. Lastly, length of time between the FAST exam
and confirmatory testing was not abstracted, thus fluid accumulations
that occurred after a negative FAST could not be accounted for.
|Overall, the FAST exam demonstrated modest sensitivity and
high specificity and accuracy for the detection of any amount of intraperitoneal
hemorrhage in hemo-dynamically unstable BAT patients. EP performed FAST showed a sensitivity of 76%, specificity of 98%,
and accuracy of 89% for any amount of hemorrhage, test characteristics
similar to Radiology performed FAST. Utilization of diagnostic
peritoneal aspirate and/or lavage in critically injured BAT patients
decreased, although the change was not significant.
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