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

Where Do We Look Sisley et al reviewed 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 Pericardial scans performed in 261 patients Sensitivity 100%, specificity 96.9% PPV: 81% NPV:100% Time interval BUS to OR: /- 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

Studynsensitivity(%)specificity(%)npv(%) Ballard et al, Boulanger et al, Chiu et al, Coley et al, Hoffmann et al, Ingeman et al, Kern et al, Liu et al, McElveen et al, McKenney et al, Rozycki et al, Rozycki et al, Rozycki et al, Shackford et al, Thomas et al, Tso et al, Wherret et al, Yeo et al, Total

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

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

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

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 pneumothorax under 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 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