Introduction to Emergency Ultrasound
Focused Assessment with
Sonography in Trauma (FAST)
Keith Boniface, MD, RDMS
Department of Emergency Medicine
George Washington University Medical Center
Objectives
Why FAST ultrasound?
How do I get the requisite images?
What are common false + and - findings?
How do I integrate FAST into my
management of trauma patients?
Background
Ultrasound used in assessment of blunt
abdominal trauma for 25 yrs in Japan
and Germany
Marked increase in use in EDs over past
10 years
ACEP, SAEM, CORD, ATLS all endorse
Armenian mass casualty experience
Goals of FAST
Rapid detection of:
– Hemoperitoneum
– Hemopericardium
– Hemothorax
Advanced/expanded
– rapid detection of pneumothorax
– identification of solid organ injury
– requires significantly more experience than
basic FAST exam
Who should we study?
Blunt and penetrating thoracoabdominal
trauma
Trauma or abdominal pain and
pregnancy
Unexplained hypotension in any patient
Advantages of ultrasound
Portable/bedside
Noninvasive
Rapid
Repeatable
No contraindications (except other
indication for laparotomy)
Other options
CT
– only for stable patients
– requires transport out of the department
according to someone else‟s schedule
DPL
– too sensitive, many nontherapeutic
laparotomies, and nonrepeatable
How good are we?
Sensitivities range from 69% to high 90‟s
Specificities 95-100% in multiple ED
studies
Time < 4 minutes in most studies
Reliably detects 200-650 cc of
intraperitoneal blood
– CT 100-250 cc
– DPL - 100,000 RBC/mm3 = 20 cc in 1 L IVF
How good are we?
Hemothorax (Ma OJ, Mateer JR, Ann Em Med „97) (Sisley AC et al, J Trauma „98)
– 96-97% sensitive, 99-100% specific
– 1.3 minutes for US, 14.2 minutes for Xray
Penetrating cardiac trauma (Plummer D et al, Ann Em Med „92)
– US group compared with retrospective
control; US by emergency physicians
– US group 100% survival; time to OR 15 min
– controls 57% survival; time to OR 42 min
RUQ
Midaxillary line in 9th-10th interspace
Orientation marker pointing towards
head
– coronal image
– can twist probe so beam parallels rib
interspace
RUQ
Kidney is retroperitoneal - posterior!
Use liver as acoustic window - cephalad!
Use respirations to move liver to where
you want it
Watch screen, not probe
Big problems with image acquisition in
RUQ come from ribs and bowel gas
RUQ
Answer two essential questions:
– Is there free fluid in Morison‟s pouch?
– Is there fluid above the diaphragm?
“Bonus” questions
– Is there evidence of liver laceration or
hematoma?
– Is there evidence of kidney disruption?
RUQ
Lateral
Head Foot
Medial
RUQ
RUQ
Diaphragm Lateral
Head Foot
Liver
Upper pole
Lower pole
kidney
Mirror Image Artifact- kidney
Liver is reflected over
bright reflector of
diaphragm - NORMAL.
Absence of this = fluid in
pleural cavity
Medial
Free Fluid in Morison‟s Pouch
Very rough rule of thumb: 0.5 cm fluid stripe = 500 cc, 1 cm fluid stripe = 1 L
Free Fluid in Morison‟s Pouch
Free Fluid in Morison‟s Pouch
More free fluid...
Diaphragm
Head
Foot
Free fluid on head side of diaphragm = pleural fluid
Another pleural fluid collection:
False + RUQ view
Is this free fluid
in Morison's pouch?
False + RUQ view
NO! This is hepatic vein
Inferior Vena Cava
RUQ view - False positives
(ascites, bladder rupture)
– Not really false +, as it is free
intraperitoneal fluid
– intraperitoneal bladder rupture goes to the
OR anyway (extraperitoneal rupture
treated with Foley catheter)
Gallbladder, duodenum, IVC, hepatic
flexure
RUQ view - False positives
Perinephric fat in obese patients
– usually inside Gerota‟s fascia - compare to
other side
Perinephric fluid 2ry renal trauma
Chronic intraabdominal inflammation
with widening of extrarenal space
RUQ view - False negatives
Small amount of fluid
– serial scans
Intraperitoneal clot
– progression from anechoic to hypoechoic
to hyperechoic
– More problematic in patients who present
12-24 hours after trauma
Subxiphoid
Utilizes liver as an acoustic window
Place transducer just below xiphoid
process
Orientation marker toward R shoulder
Point beam toward L shoulder
Overhand grip to get flat enough angle
Normal Subxiphoid
Liver
RV
LV
RA
LA
Pericardial Effusion
Effusion
RV
RA
Subxiphoid
False negative if large hemothorax
– re-check after chest tube
False positive
– Anterior pericardial fat pad
never found posteriorly
check multiple views
Blaivas M et al, Potential errors in the diagnosis of pericardial effusion on trauma ultrasound for
penetrating injuries. Acad Emerg Med 2000
Parasternal long
An alternative view if very obese/poor
subxiphoid window
Probe is placed in the 2nd-4th
intercostal space near the sternum
Beam angled toward R shoulder
Orientation marker toward L hip
Parasternal long
Parasternal long
RV
LVOT
LV Aortic valve
Mitral valve
LA
Posterior
pericardium
Descending aorta
Parasternal long
The descending aorta is an important
landmark
Regardless of how large a pericardial effusion
is, it will always "tuck in" between the aorta
and the heart
Pleural effusions will dive down posterior to
the descending aorta
This distinction is important if you are
debating doing a pericardiocentesis vs chest
tube!
Parasternal long
Parasternal long
RV
Thickened
septum
LV
Visceral
pericardium
Pericardial effusion
tucking between aorta
and heart
Aorta
Parietal pericardium
Parasternal long
Pleural Effusion
Parasternal long
RV
LVOT
LV
Aorta
Pleural effusion
diving posterior
to aorta
Pleural Effusion
LUQ
Posterior axillary line at 9th-10th interspace
Breath holds to move spleen down
Tougher view b/c spleen is much smaller
acoustic window than liver, so more gas
If kidney seen but no spleen, slide one
interspace cephalad
LUQ
Look around spleen and kidney for fluid
– fluid tends to accumulate in subphrenic
space initially, so essential to see
spleen/diaphragm interface
Look above diaphragm
Fan through spleen to look for injury
– splenic lacerations often hyperechoic as
opposed to anechoic
LUQ
LUQ free fluid
Normal splenorenal recess
Hemoperitoneum
LUQ – free fluid
LUQ free fluid
LUQ - fractured spleen
Laceration
Free fluid
Diaphragm
Normal
splenorenal
recess
LUQ - free fluid
70 y/o driver of car
Tboned on driver's side
LUQ - free fluid
Diaphragm
Fluid on head side
of diaphragm =
pleural fluid
Spleen
Kidney
LUQ - free fluid
LUQ - more fluid
LUQ - more fluid
LUQ
False positives
– Accessory splenic lobules
– Fluid-filled stomach or splenic flexure
False negatives
– Failure to look at subphrenic recess
Pelvic
Place probe just superior to symphasis
Sagittal midline - aim beam 0-30
degrees into pelvis with orientation
marker towards head
Transverse midline - rotate 90 degrees
to R and fan up and down
Pelvic
Increase depth
Decrease gain b/c of minimal attenuation
Full bladder - do before Foley, add 250
cc saline through Foley, or repeat when
bladder is full
Look for anechoic areas and free floating
loops of bowel in cul-de-sac and lateral
to bladder
Pelvic
Not enough depth -
can miss fluid collections
in cul-de-sac
Pelvic
Pelvic
Pelvic free fluid
Free fluid
Pelvic free fluid
Pelvic free fluid
Lower uterus
Small amount
of physiologic
fluid
Pelvic
False positives
– seminal vesicles - paired hypoechoic
structures just posterior to the male bladder
– prostate
– fluid filled bowel without peristalsis
– extraperitoneal blood in pelvic fracture
– ovarian cyst
False negative
– empty bladder
Blunt Abdominal Trauma Algorithm
Blunt Abdominal
Trauma
Unstable Indications Stable
for OR
FAST OR FAST
Free fluid No free fluid Free fluid No free fluid
OR ? Pelvis, Chest, Expedited CT CT
Long bone fx, Blood loss or
or other cause shock serial exams
Resuscitate and redo FAST
Special situations
Pediatrics - good for risk stratification,
but lower utility - even markedly +ve
FAST pts can be observed
Penetrating abdominal trauma - high
false negatives, but if +ve, that
indicates peritoneal violation and OR
Pregnancy - not sensitive enough to
detect abruption; needs continuous
fetal monitoring by OB
Pearls
Serial ultrasound exams
Ascites? Nodular liver, thickened GB
wall, enlarged caudate lobe, engorged
portal vein
LUQ - put the probe cephalad and
posterior
Pelvic - increase depth and decrease
gain
Pitfalls
Doing FAST exam on someone who
needs the OR
Overreliance on initial -ve FAST and
failure to repeat study
Failure to recognize limitations
– obese, massive SQ emphysema
– solid organ injury
– pregnancy - cannot rule out abruption
– pre-existing ascites as false +ve