Focused Assessment with Sonography for Trauma: Methods, Accuracy, and Indications
Section snippets
Anatomic review
Intra-abdominal views on FAST are based on 3 dependent areas within the peritoneal cavity in which free fluid is most likely to accumulate when the patient is in the supine position: (1) perihepatic, subphrenic and hepatorenal recess/Morrison pouch; (2) perisplenic, splenorenal fossa/subphrenic; and (3) pelvis. The minimum volume of free intraperitoneal fluid required for detection by FAST has been reported to range from 100 to 620 mL (Table 1).4, 5, 6, 7, 8 Volumes at the lower end of the
Patient Position
The patient is preferably examined in the supine position. Other positions (Trendelenburg, reverse Trendelenburg, and decubitus) may facilitate pooling of fluid in dependent regions, thereby potentially increasing detection yield, and should be considered if the clinical scenario permits.
Transducer
Transducer selection depends on the size of the patient. For a typical adult, sound wave penetration must be at least 20 cm. Therefore, a lower-frequency transducer is selected, such as 3.5 to 5 MHz curved
FAST examination views
A typical FAST examination incorporates a minimum of 4, but up to 6, views (Fig. 1).13 When imaging a patient, the left side of the display screen should always be the patient’s right side (Fig. 2). The screen should reflect cranial to caudal going from left to right when displaying a longitudinal view (Fig. 3).
Image optimization
Image quality and overall sensitivity of the examination may be optimized by manipulation of factors influencing signal strength and image acquisition.
Gain
Gain refers to the amplification of receiver signals from deeper tissues to compensate for increased attenuation compared with near-field structures. Gain can be adjusted to brighten or darken the whole image. The time gain compensation (TGC) curve can also be adjusted to brighten or darken segments of the image. The TGC curve requires frequent adjustments because different structures attenuate sound differently.
Focal Zone
The focal zone is the depth at which the sound waves have narrowed, resulting in
Clinical applicability
Two decades after the incorporation of ultrasonography in trauma, its precise role remains unclear. Much of this can be attributed to the comparative reference standards (DPL, computed tomography [CT], laparotomy, clinical observation) and end points (fluid detection, intervention), by which its effectiveness has been judged. In addition, advances in skills and technology have confounded the simple initial intent “detection of free fluid” and use as an “adjunct, not substitute” for preexisting
Pediatric trauma
Few studies on the efficacy of ultrasonography in children with abdominal injury have been reported. Scaife and colleagues32 conducted an electronic survey of the use of FAST at American College of Surgeons (ACS) level 1 trauma centers, National Association of Children’s Hospitals, and freestanding children’s hospitals. FAST examinations were used in 96% adult-only institutions, 85% combined adult and pediatric centers, and 15% children’s hospitals. The largest impediment to the use of FAST in
Accreditation
After an initial 8-hour course that included didactic and hands-on training with FAST, Thomas and colleagues37 reported a sensitivity of 81%, specificity of 91%, and overall accuracy of 98%.
At The International Consensus Conference in 1999,22 the majority viewpoint supported an 8-hour (4 theoretical, 4 practical) minimum training period to learn the FAST procedure, with a minimum of 200 supervised patient examinations. A minority viewpoint was that as few as 50 examinations were sufficient. The
Future directions
Recent technological advancements in sonography can improve and expand the FAST examination in appropriate clinical settings. Three-dimensional sonography allows for multiplanar imaging, enabling acquisition of a plane through a desired point of interest that may not be accessible with conventional sonography because of size or location of the acoustic window. It also provides a new display of the images that can improve the ability to determine spatial relationships between normal and abnormal
Summary
FAST has had a significant effect in the management of abdominal trauma, with its ease of rapid performance, portability, and noninvasive nature, resulting in a significant increase in its use over the past 2 decades. Extending its use from the original intent as a diagnostic adjunct for detection of free intraperitoneal fluid and pericardial effusion to a stand-alone diagnostic modality has raised questions regarding its validity and optimal role. FAST remains an invaluable adjunct in the
References (42)
- et al.
Ultrasound for the detection of intraperitoneal fluid: the role of Trendelenburg positioning
Am J Emerg Med
(1999) - et al.
Ultrasound detection of pneumothorax
Clin Radiol
(1999) Ultrasound in abdominal trauma
Emerg Med Clin North Am
(2004)- et al.
Emergency department ultrasound in the evaluation of blunt abdominal trauma
Am J Emerg Med
(1993) - et al.
The UHP ultrasound protocol: a novel ultrasound approach to the empiric evaluation of the undifferentiated hypotensive patient
Am J Emerg Med
(2001) - et al.
Use of focused abdominal sonography for trauma at pediatric and adult trauma centers: a survey
J Pediatr Surg
(2009) - et al.
Absent peritoneal fluid on screening trauma ultrasonography in children: a prospective comparison with computed tomography
J Pediatr Surg
(2001) - et al.
Physical examination as a reliable tool to predict intra-abdominal injuries in brain-injured children
Am J Surg
(2006) - et al.
Ultrasonic scanning in the diagnosis of splenic haematomas
Acta Chir Scand
(1971) - et al.
A prospective study of surgeon-performed ultrasound as the primary adjuvant modality for injured patient assessment
J Trauma
(1995)
Advanced trauma life support
Quantitative sensitivity of ultrasound in detecting free intraperitoneal fluid
J Trauma
Defining the learning curve for the focused abdominal sonogram for trauma (FAST) examination: implications for credentialing
Am Surg
Evaluation of ascites by ultrasound
Radiology
Sensitivity of transabdominal ultrasonography in detection of intraperitoneal fluid in humans
Eur Radiol
Ultrasonography for the evaluation of hemoperitoneum during resuscitation: a simple scoring system
J Trauma
Hemoperitoneum score helps determine need for therapeutic laparotomy
J Trauma
Predicting the need for laparotomy in pediatric trauma patients on the basis of the ultrasound score
J Trauma
Ultrasound: the requisites
Not so FAST
J Trauma
Does the presence of ultrasound really affect computed tomographic scan use? A prospective randomized trial of ultrasound in trauma
J Trauma
Cited by (61)
Focused assessment with sonography for the trauma patient
2023, Current Therapy of Trauma and Surgical Critical CarePoint-of-Care Ultrasound in the Intensive Care Unit: Applications, Limitations, and the Evolution of Clinical Practice
2022, Clinics in Chest MedicineA Discrete-Event Simulation Model of Hospital Patient Flow Following Major Earthquakes
2022, International Journal of Disaster Risk ReductionToo fast, or not fast enough? The FAST exam in patients with non-compressible torso hemorrhage
2019, American Journal of SurgeryAcute mesenteric ischaemia: A case of expedited diagnosis and management using point-of-care ultrasound
2018, African Journal of Emergency MedicineCitation Excerpt :Ultrasound represents a favourable alternative when utilised for rapid triage or diagnosis, at the bedside. Similar to the FAST [6] protocol, (utilised to bypass CT in unstable trauma patients with sonographic evidence of intraperitoneal haemorrhage), we propose the use of point-of-care ultrasound for initial evaluation in patients with an acute abdomen. Cases can, then, be triaged for early operative management and, when appropriate, may subvert the requirement for diagnostic CT.
Point-of-Care Ultrasound in the Intensive Care Unit
2018, Clinics in Chest MedicineCitation Excerpt :Importantly, the ultrasound examination does not require an unstable patient to be transported, such as with a CT or MRI scan. Although the focused assessment with sonography for trauma (FAST) protocol has been widely adapted for trauma patients over several decades, there is less of an accepted standard for the critically ill medical patients.97 Emergency medicine physicians are familiar with the rapid ultrasound in shock (RUSH) examination that is designed to quickly investigate patients in unexplained shock.
The authors have nothing to disclose.