Emergency Ultrasound in
Trauma
Introduction
• Whose done a formal course?• Who learnt at the bedside?• Who thinks they know what they are doing?• What is the role of FAST in (signifcant) blunt
trauma?
Introduction
• Brief history• Over view view of FAST• E-FAST• Pearls and pitfalls • The role of FAST in patient management
History
History of The FAST EXAM
• Bedside ED US in trauma became routine in Japan and Germany in the 1970’s
• ED physicians in the USA began using US in the 1980’s
• Now an integral part of ATLS• Since 2001, all ED residents in the USA do
formal US training
FAST is Focussed
• ED ultrasound asks focussed (yes or no questions)
- does this patient have a AAA - does this patient have a gallstone - does this patient have an abscess• The FAST exam only asks “does this patient
have free fluid?” - yes / no / indeterminate
FAST is Focussed
• We don’t care where the fluid comes from - and we can’t tell• We are not looking for organ injuries - some ED US “experts” are now talking about diagnosing specific injuries - sens is too low
“ The most important preoperative objective in the management of the patient with trauma is to ascertain whether or not laparotomy is needed, and not the diagnosis of a specific organ injury”
Why Look For Fluid?
• In trauma, free fluid is assumed to be blood• Bleeding into the abdomen is the leading
cause of preventable death in trauma• In the standard FAST we look for fluid in the
abdomen, pleural space and pericardium• In the E-FAST we add looking for a
pneumothorax
Aims of FAST
• Main aim is to identify who needs to go to the operating theatre “stat”
- the unstable patient with a positive FAST• Some advocate using the FAST in stable
patients to determine - who needs a CT scan - who can be discharged This is controversial (FAST does not rule out injuries)
Aims of FAST
• Also used for triage in mass casualty situations - Iraq and other illegal wars - Haiti - Armenian Earthquake in 1988 performed 400 FAST’ sin 48 hours (1 every 10 minutes)
Free Fluid
• In trauma, we assume that free fluid is blood.• It may not be - urine - bowel contents - still need a laparotomy• Ascites (use clinical judgement)• Pysiological fluid in a pre-menopausal woman
When Do We Perform the FAST
• Looking for bleeding - part of “C” in the primary survey• Need to be a bit flexible - priority in penetrating chest injuries?• Needs to be done before - insertion of IDC - the log roll
When Do We Perform The FAST?
• With small modern machines you can do the FAST without getting in the way
• Can do it whilst other procedures are being performed
• Can repeat as often as needed - patient condition changes - as a routine to improve sensitivity
Serial FAST’s
• Backbourne 2004 et al - sens of initial FAST vrs CT: 32% (spec = 98) - sens of repeat FAST vrs CT: 72% - 26 patients has a negative initial scan and a positive repeat scan (n = 108) - of these 10 went to laparotomy - no patient with a negative FAST at 4 hours developed “significant” intraperitoneal bleeding - but does this mean that they are safe to discharge?
Where Do we Look
• We know where to look• We know why we are looking in that location• We need to go over it because we forget it
when we put the probe on the patient - can result in false-negative scans when the amount of free fluid is small
Where Do We Look
• Trauma patients arrive in a supine position• Fluid accumulates in anatomically dependent
areas
Dependent Areas in The Supine Patient
The Pelvis
The Pelvis
Where Do We Look
• Sisley et al 1998 - reviewed 10000 patients with positive FAST - RUQ was positive in 86% - LUQ: positive in 55% - Pelvis: positive in 43%
Know how to scan the RUQ.
Dogs Love CPAP
How Much Fluid Can We Detect
Branney, S.W. et al: Quantitative sensitivity of ultrasound in detecting free intraperitoneal fluid J Trauma:1995: 39
• Peritoneal lavage fluid infused in 100 patients• Simultaneous scan of Morison’s pouch
– By physicians ( Surgery,EM, Radiology)– Blinded to volume and rate of infusion– Mean volume of detection: 619cc– Sensitivity at 1 liter: 97%– 10% physicians detected less than 400cc
How Much Fluid Can We Detect
• Lots of studies• Location dependent• Position dependent• Pleural space: < 50 to 100 ml• Pelvis: 150 ml• RUQ: 200 to 600 if supine < 100 if right lateral decubitus ? 5 degrees head down
How Much Fluid Can We Dectect?
• Not that important• What is important - unstable and free fluid = laparotomy - negative / indeerminate scan = repeat latter
Where Do We Look: The Order
• Doesn’t matter• Most people start in the URQ - money shot - stop if positive• Exception is if there is penetrating trauma to
the chest - look for pericardial fluid first - clinically silent and can crash
Trauma Study
The role of ultrasound in patients with possible penetrating cardiac wounds: a prospective multicenter study.
Rozycki GS: J Trauma. 1999
• Pericardial scans performed in 261 patients• Sensitivity 100%, specificity 96.9%• PPV: 81% NPV:100%• Time interval BUS to OR: 12.1 +/- 5.9 min
Where Do We Look: The Order
• More important is to scan each area thoroughly
• Don’t get sucked in to trying to complete the FAST quickly
- systematic look for occult haemorrhage (SLOH)
Don’t get distracted by storing images.
FAST: Sensitivity & Specificity
A Quick Rant
Imaging Sensitivity
• Values quoted in the literature for sensitivity / specificity don’t help my practice
- too many variables• “Modern CT scanners have a sensitivity of 98%
for SAH” - what generation scanner - how many detectors - who read the scan - timing of the scan - what was the gold standard
Study n sensitivity(%) specificity(%) npv(%)
Ballard et al, 1999 102 28 99 85
Boulanger et al, 1996 400 81 97 96
Chiu et al, 1997 772 71 100 98
Coley et al, 2000 107 38 97 78
Hoffmann et al, 1992 291 89 97 93
Ingeman et al, 1996 97 75 96 92
Kern et al, 1997 518 73 98 98
Liu et al, 1993 55 92 95 84
McElveen et al, 1997 82 88 98 96
McKenney et al, 1996 996 88 99 98
Rozycki et al, 1993 470 79 96 95
Rozycki et al, 1995 365 90 100 98
Rozycki et al, 1998 1227 78 100 99
Shackford et al, 1999 234 69 98 92
Thomas et al, 1997 300 81 99 98
Tso et al, 1992 163 69 99 96
Wherret et al, 1996 69 85 90 93
Yeo et al, 1999 38 67 97 93
Total 6324 75 98 94
Ultrasound
• Well known to be user dependent• For FAST, so few are positive it’s hard to get a
feel for how skilled you are - unless you know a friendly peritoneal dialysis patient
Sensitivity & Specificity
• In general - sensitivity 80 to 90% - specificity over 95%• In the unstable patient, free fluid is 100%
sensitive for an injury requiring a laparotomy - 3 papers - total n = 133
Pearls & Pitfalls: General
• Free fluid can be subtle - can track into small places - can slip between loops of bowel and viscera• Some put head down for 5 minutes• Look carefully between - the diaphragm and liver - diaphragm and spleen
Pearls & Pitfalls: General
• Free fluid has straight edges and may be pointy
• False positives are often round and appear contained
- gallbladder - ICC - fluid in the bowel
Pearls and Pitfalls: General
• Fresh blood is black• Blood can clot within minutes - takes on the same density as soft tissue - can be missed - need to consider how long since the accident
Pearls and Pitfalls: General
• Beware of perinephric fat - can be mistaken for free fluid or clotted blood• Usually a speckled appearance (internal
echos) - look at the other kidney - usually overweight patient - roll them and see if it moves
Pearls and Pitfalls: General
• Predictors of false negative FAST - Subcutaneous emphysma - Pelvic Fracture - Spinal fracture
• Consider CT.
Pearls and Pitfalls: URQ
• Consider 5 degrees head down• There 4 areas to examine - Morison’s Pouch - inferior pole of kidney (right paracolic gutter) - under the diaphragm - lung base • Rare to see all 4 in one view - scan all 4 areas
Pearls and Pitfalls: RUQ
• Lung base - look for mirror artefact - loss of mirror aretact 96% sens & 100% spec for haemothorax (Ma 1997)
Normal URQ
URQ: Haemothorax
Pearls and Pitfalls:
• False positives - gallbladder - IVC - perinephric fat - fluid in duodenum - renal cyst - adrenal gland (bright white margins)
URQ: Free Fluid
URQ: Free Fluid
Perinephric Fat
Pearls and Pitfalls: ULQ
• ULQ is not a mirror image of the RUQ• It is a hard view - kidney is more posterior (deep) - kidney is more cranial - (full) stomach gets in the way• Hand may be touching the bed
Pearls and Pitfalls: ULQ
• You look in 4 areas - pleural space - sub-diaphragmatic - spleno-renal recess - inferior pole of kidney
Pearls and Pitfalls: ULQ
• Fluid may only be seen between the diaphragm and spleen
- look carefully - ask them to breath in and out deeply which may move the diaphragm away from the spleen and reveal free fluid
ULQ
Pearls and Pitfalls: ULQ
• False positives - renal and splenic cysts - fluid in stomach - adrenal gland - blood vessels at the splenic hilum
ULQ: Free Fluid
ULQ: Free Fluid
Sub-diaphragmatic Fluid
LUQ: Pleural Effusion
Pearls and Pitfalls: Suprapubic
• Need a full bladder - do before the IDC - try a bag of NS as a window if bladder empty• Can put head up for a few minutes• You get posterior acoustic enhancement - if image too bright it will mask fluid - turn down the gain and TGC
Pearls and Pitfalls: Suprapubic
• In general - longitudinal view: fluid to left of screen - transverse view: fluid beneath bladder
• Bladder may be hard to locate on obese patients
- usually lower than you think
Pearls and Pitfalls:
• False positives - seminal vesicles - impacted rectum - physiological fluid in a young female - iliopsoas muscles
Longitudinal Pelvic Female: Normal
Female Pelvis: Free Fluid
Female Pelvis: Lots of Fluid
Transverse Female Pelvis: Normal
Transverse Female Pelvis: Free fluid
Pearls and Pitfalls: Subcostal
• Important view in penetrating chest trauma• Can be difficult to obtain good views - fat - pain - uncooperative - probe should be almost flat on the abdomen - increase depth?• If you can’t get a good view, try PLAX
Pearls and Pitfalls: Subcostal
• False positive: pericardial fat pad - usually has speckled appearance - often just anterior - an effusion usually lies in a dependent position
Pearls and Pitfalls:
• False positive: pleural effusion - in the PLAX view - find the aorta - fluid anterior to the aorta is pericardial - fluid deep to the aorta is pleural
Sub-costal View
Pericardial Effusion
Pericardial Effusion
E-FAST
Erect Pneumothorax
Supine Pneumothorax
• Lung falls posteriorly• Air rises to the highest point• Air seen near the
diaphragm first
Etching of the Diaphragm
Deep Sulcus Sign
HOW ELSE CAN WE DIAGNOSE A PNEUMOTHORAX?
• Supine CXR has a low sensitivity • CT has a high is sensitivity but…….
CT is a Cold & Lonely Place to Die
THE E-FAST• Perform FAST as usual• Then scan the chest for a
pneumothorax - sens US = > 90% - sens supine x-ray = 28 – 65%
Only excludes a pneumothoraxunder the probe.
Normal Pneumothorax
Sea-shore Sign Barcode Sign
Pearls & Pitfalls
• Slung sliding excludes a pneumothorax (under the probe)
- the reverse is not true• Comet tails exclude a pneumothorax - the reverse is not true• Look at the highest point of the chest - additional views will increase the sensitivity of the scan (slide more at bases)
Pearls & Pitfalls
• Absence of lung sliding may be - a pneumothorax - adhesions - pleurodesis - right mainstem intubation - hyper-inflated asthma! (lung pulse present)• Consider the clinical context
Role of FAST
• No debate about - role in penetrating chest injury - unstable patient• Practices vary for the stable patient
Pericardial Effusion
• May be stable on arrival with a normal physical exam
• Can then rapidly decompensate• We can diagnose an effusion before they
decompensate• Rozycki et al 1996 - from US to OT in a mean time of 12 minutes
Unstable Patient & Negative FAST
• Look for non-abdominal blood loss - long bone - retroperitoneum - pelvic injury - external - cardiac event - spinal shock
Unstable Patient & Negative FAST
• DPL?• Serial FAST exams?• CT is patient stabilises• OT anyway?
The Stable Patient
• Jeremy our beloved trauma leader does not believe that a stable patient should not get a FAST
- clinically suspicious: get a CT• Others argue that a positive FAST - gives an early warning of potential decompensation - guide to who gets a CT
Penetrating Trauma
• No concensus opinion• As per blunt trauma?
• Stable and no peritonism: CT• Unstable or peritonism: OT
Conclusions
• It’s not a race; Slowly and systematically assess all areas
• The FAST asks only “Is there free fluid?”• The E-FAST adds “Is there a pneumothorax?”• A negative FAST does not exclude intra-
abdominal injury• A positive FAST in an unstable patient wins a
trip to the OT
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