2. FAST Exam
Introduction
Ultrasound Physics
Technique
Indications for FAST exam
Performing a FAST exam
Limitations
Questions
3. What is the FAST exam?
Focused Assessment by Sonography in Trauma
Focused exam using ultrasound to diagnose
hemorrhage in a trauma setting
Ideally takes < 3 min
4 primary views
RUQ
LUQ
Subxiphoid
Suprapubic
4. Basic Ultrasound Physics
Ultrasound is a spectrum of sound frequencies
above the human hearing range.
Molecules must be present for sound to exist.
Every object has an echogenicity. When sound
waves hit the object some are transmitted
through and some bounce back.
Every substance will respond differently to the
sound waves striking it’s surface. This occurs at
every sound-to-sound interface and the
reflection of sound waves can be used to create
and image.
5. Technique
Goal: to identify blood in
body cavities where it is
not supposed to be
Unclotted blood appears
black on US
Clotted blood appears gray
Abdominal probe with
small footprint (between 1-
3 cm) with range of
frequency between 2.0 Hz
and 5.0 Hz
Scan 4 areas
RUQ
Subxiphoid
LUQ
Suprapubic
6. Indications
Blunt thoracoabdominal trauma
Penetrating thoracoabdominal trauma
Suspected pericardial tamponade
Trauma patient with hypotension on
unknown etiology
Thoracoabdominal trauma in a pregnant
patient
7. Right Upper Quadrant
Sagittal view obtained by
placing probe either in the
midclavicular line on the
lower rib cage or below
the right costal margin
May have to move probe
laterally to avoid gas in
hepatic flexure
Air-filled lung creates
reflection artifact in which
lung appears to be
composed of liver
parenchyma
Scan for black fluid in
potential spaces
13. Subxiphoid
Probe placed under
xiphoid almost parallel
with skin surface directed
towards patient’s left
shoulder
Parasternal view may be
used when supxiphoid
unable to be obtained
Consider pnuemothorax
when unable to obtain
images of heart and no
apparent reason
17. Left Upper Quadrant
Most technically
difficult to obtain
Probe placed parallel
with ribs in posterior
axillary line
Scan potential spaces
between diaphragm
and spleen and
spleen and kidney for
free fluid
23. Suprapubic
Entire pelvis should be
scanned from top to
bottom with transducer in
transverse place and
them side to side with
transducer in sagittal
plane
Pouch of Douglas is the
most dependent site in
peritoneal cavity
First sign of blood is often
two small black triangles
on either side of rectum
“Bow tie sign”
29. Limitations
Retroperitoneal bleeding
Inadequate volume of fluid
Not enough time elapsed since trauma to
demonstrate bleeding
Solid organ trauma with encapsulated bleeding
Image quality dependent on quality of US
machine and probe, body habitus of patient,
physical injuries
Scan and interpretation are operator dependent
Ultrasound is a spectrum of sound frequencies above the human hearing range. Molecules must be present for sound to exist. Every object has an echogenicity. When sound waves hit the object some are transmitted through and some bounce back. Every substance will respond differently to the sound waves striking it’s surface. This occurs at every sound-to-sound interface and the reflection of sound waves can be used to create and image.
Unclotted blood allows passage of transmission of ultrasound waves without echoes. Clotted blood creates echoes and thus appears gray. Foot print is the area of skin that the probe covers. Good to have small probe b/c you can look b/n ribs if you need to. Generally you can use 3.5 hz. You can use higher frequencies in thinner patients. Lower frequencies will give better resolution in heavier patients. 1) subxiphoid - to visualize the heart, 2) RUQ - to visualize Morrison's pouch and paracolic gutter, 3) LUQ - to visualize the spleeno-renal recess and paracolic gutter, 4) suprapubic - to visualize Douglas' pouch. Many people start in RUQ b/c this is where fluid is most likely to be. Some start subxiphoid in order to early see pericardium/tamponade also allows for adjustment of the gain. - fluid most likely to be in RUQ due to anatomical and gravitational considerations. People are generally supine. Organs in pelvis relatively well protected. Abdominal organs usually injured. Blood flows into Morrison’s pouch (space b/n liver and kidney) Generally, if hemorrhage is below the bony pelvis it will flow caudad and above it will flow cephalad.
Usually only do below right costal margin in patients able to take deep breaths. Lung is filled with air which is highly reflective leading to artifact. Abscense of this artifact suggests hemothorax. Some sonographers as they gain experience will scan solid organs for areas of abnormal echogenicity which would suggest parenchymal injury. This is not part of FAST exam.
Subxiphoid may be impossible due to patient’s body habitus or physical injuries.
When having trouble getting this view, it is usually because the probe is not posterior enough or superior enough. In both the LUQ and RUQ, it is usually necessary to get multiple images in order to identify all of the required structures.Getting them all in a single image The features of the LUQ view are very similar to those of the RUQ, with the normal pleural space appearing as if there were spleen both above and below the diaphragm.
Mesenteric artery lac
In a normal transverse suprapubic view, the pouch of Douglas is the most dependent site (standing or supine) in the entire pentoneal cavity The first sonographic sign of blood in the pelvis is often two small black triangles on either side of the rectum the so-called bow tie sign. The entire pelvis should be scanned from top to bottom with the transducer in the transverse plane, and then from side to side with the transducer held in a sagittal plane.
