Is the FAST exam reliable in severely injured patients?
Introduction
Focused assessment with sonography for trauma is an integral part of the evaluation of blunt trauma patients. Fast, portable and easily integrated into the resuscitation of the trauma patient, ultrasonography (US) has become a standard screening tool widely used by most modern trauma centres.
Most investigators agree that US offers high sensitivity (60–98%), specificity (84–98%) and negative predictive value (NPV) (97–99%).8, 18, 31 Although this has led to widespread acceptance of US as an initial screening tool, the clinical conditions in which it is most accurate in the assessment and management of trauma patients have yet to be determined.
Highly sensitive and accurate for the detection of injuries requiring intervention in haemodynamically unstable patients, FAST may underestimate intra-abdominal injuries in stable patients with blunt abdominal trauma.13 The US evaluation of blunt trauma patients with simultaneous head, chest and pelvic injuries may become even more challenging. Ballard and co-workers studied 102 patients with spine and pelvic fractures who had FAST examinations, and reported 13 false negative (FN) US results for detecting free fluid in 70 patients with pelvic fractures. Based on these data they concluded that patients with pelvic ring fractures should undergo a CT scan of the abdomen.3 Diminished accuracy of US was also found in patients with multiple trauma and low GCS.26 Yoshii et al. studied 1239 patients, and reported 19 (2%) FN and 44 (11%) false positive (FP) results of US exam. All patients in the study were confirmed to have free fluid and intra-abdominal injury by either subsequent laparotomy or CT scan. In all FP results, minimal free fluid was identified by US and not seen in either laparotomy or CT scan. Of these, 18 patients had chest trauma.31
We hypothesised that multiple injured blunt trauma patients with a high Injury Severity Score (ISS) will have an increased rate of FN and FP FAST results in detecting free fluid and thus a decreased accuracy for the assessment of blunt abdominal trauma.
This study was approved by the University of Miami Institutional Review Board.
Section snippets
Patients and methods
Data from the trauma registry of a Level 1 trauma centre were retrospectively reviewed.
All haemodynamically stable (systolic blood pressure > 100 mmHg, heart rate < 110) blunt trauma patients who underwent both US as a part of initial assessment and CT scan of the abdomen from 2000 to 2005 were included in the cohort. All patients were divided into 3 groups according to their ISS—1: ISS 1–14; 2: ISS 16–24; 3: ISS ≥ 25. The age, gender, mechanism of injury, physiologic parameters, laboratory test
Results
The Ryder Trauma Center admitted 9870 patients from 2000 to 2005. Excluded from the study were 2997 patients with penetrating trauma. An additional 2580 patients did not undergo either an US examination or CT scan, as per the attending trauma surgeon's discretion, were also excluded. US was performed on 5686 patients with blunt trauma. After excluding 1112 haemodynamically unstable patients (systolic blood pressure <90) and 1393 patients who did not have a CT scan, 3181 haemodynamically stable
Discussion
Although US has gained significant popularity, the clinical conditions in which it is most accurate in the assessment and management of trauma patients have yet to be determined. The benefits and limitations of US following blunt abdominal trauma have been extensively discussed in recent literature. Relevant literature supports the view that US is a good screening tool for blunt abdominal trauma.4, 9, 11, 12
In current practice, US has an important role in the identification of unstable trauma
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