Author: Lynette Hassall DMU AMS MLI.
According to the Australasian College for Emergency Medicine (ACEM), clinician performed bedside ultrasound is a ‘limited, goal directed examination’, designed and used to answer ‘specific clinical questions’. (1)
The indications for performing a FAST or eFAST include:
Trauma in Pregnancy (2)
It is quick to perform, and should not be used as a ‘stand-alone’ examination – it should be repeated at regular intervals to check the status of the patient.
The clinician performed eFAST scan is not intended to replace formal diagnostic ultrasound tests, nor is it designed to diagnose solid organ injury or other pathology.
The FAST scan should be documented, by saving images of the standard views, plus any additional images to document pathology.
If you cannot see an area clearly, you cannot comment on this part of the examination. The decision on treatment path for the patient is then made on your physical examination, whether the patient is stable or not, the results of other tests, and your clinical opinion. It does not rest alone on what the ultrasound shows.
The ACEM also recommend practical training courses, mentoring and a process of accreditation to ensure that the scans are being performed by clinicians who are competent in this technique.
Benefits of Performing eFAST:
Decreases the time to diagnosis for acute abdominal injury in Blunt Abdominal Trauma
Helps accurately diagnose, and assess degree of haemoperitoneum.
Can be integrated into the primary or secondary survey and can be performed quickly, without having to move the patient (or take them to another area).
Can be repeated for serial examinations.
Is safe in pregnant patients and children.
Leads to fewer diagnostic peritoneal lavages. (3)
The eFAST answers very simple clinical questions:
Is there significant free fluid in the pericardial cavity?
Is there free fluid in the peritoneal cavity?
Is there free fluid in the chest cavity?
Is there a pneumothorax?
What constitutes a positive eFAST?
Any fluid visible in any of the potential spaces is abnormal.
Loss of the sliding of the lung edge is abnormal.
What next? – your clinical skills dictate course of action
- Morrisons Pouch
- Spleno-Renal angle
- Pelvis – Longitudinal / Transverse
- Pleura Bilateral
The four abdominal views comprise:
- The hepato-renal interface (Morrison’s pouch) Angle and the right diaphragm.
- The spleno-renal interface and left diaphragm.
- Pelvis in both planes – I. Longitudinal II. Transverse
- Pericardial: Subxiphoid or intercostal views of the pericardium
- Pleura Bilateral: The fifth view is the pleura (bilaterally)
The ACEM recommends FOUR views of the abdomen, and then an extension of the examination to the pleura for the fifth.
1. Choose an appropriate Transducer – To begin, choose either a Curved array or a Phased array.
The curved array will produce a wider near field of view, the phased array will produce a ‘pizza slice’ shaped image with a narrower near field, and wider far field of view
(also called curvilinear)
(particularly useful for intercostal views)
2. Enter the Patient Details in the machine
3. Choose an ‘Abdominal’ Preset
4. Choose the appropriate Frequency setting:
Resolution – for a slim patient or a child
General – this is an average setting for most patients
Penetration – for a large or obese patient
5. Set the DEPTH – the area you are assessing should fill the screen.
6. Adjust the GAIN settings so that you do not obscure small pockets of fluid with a setting that is too bright – Remember in Ultrasound you want to take a walk on the ‘Dark side’ of the Force and turn the gain down. (if available, try using the AUTOGAIN function, but remember that you may still need to adjust the settings if the image on the screen requires it).
1. RIGHT UPPER QUADRANT - Morrison's Pouch View
a. The transducer is placed at approximately the mid axillary line.
b. Change your grip so that the transducer is held comfortably, close to the face of the transducer.
c. The marker end (top) of the transducer is placed at the level of the xiphisternum
d. The transducer is rotated so Xyphisternum that the non marker end is slightly anterior, parallel to the ribs, in the intercostal space.
e. From this position the beam is directed posteriorly toward the bed.
f. Optimize the image – appropriate depth and gain for best resolution
g. Slide the probe cephalad or caudal to obtain a window between the ribs to view Morisons Pouch
h. Note should be made of the normal mirror image artifact above the diaphragm – if this is absent a pleural effusion, or collapse and consolidation, is present in the lung Remember that we are interrogating a volume of tissue so the transducer should be held in place and the beam should be fanned from anterior to posterior.
i. Fluid may sit in the anterior recess of the subphrenic space so observe the potential space between anterior surface of the liver and anterior abdominal wall
j. This view is completed by sliding the transducer caudally to observe the lower pole of the right Kidney and the paracolic gutter.
2. LEFT UPPER QUADRANT - Splenorenal Angle
The transducer is again placed at approximately the left mid axillary line, however, for this view the middle of the transducer should be placed at the level of the xiphisternum.
The spleen is a smaller organ than the liver and so the spleno-renal angle will be slightly more superior than Morrisons Pouch.
The transducer is rotated slightly so that the non marker end is slightly anterior, between the intercostal spaces.
From this position the beam is directed slightly posteriorly, towards the bed.
Slide the transducer cephalad or caudad to obtain a window between the ribs.
Assess Image optimization – do you need to change the depth?
Note should be made of the lung echogenicity for presence of a pleural effusion, or collapse and consolidation.
The transducer is held in this position and the beam is fanned anterior to posterior to view the entire volume of tissue.
This view is completed by sliding the transducer caudally to observe the lower pole of the Left Kidney and the paracolic gutter.
- Both longitudinal and Transverse views of the pelvis are performed.
- The transducer is next placed in midline in the sagittal plane, heel of the probe on the superior symphasis pubis
The transducer is next placed in midline in longitudinal (Sagittal) to view the suprapubic region.
Place the transducer so that the heel end is resting on the pubic symphysis.
Point the beam straight down toward the table.
Optimize the image – is the depth and gain correct?
Identify landmarks – the symphysis pubis, bladder (thick wall if empty) and prostate(male) or vaginal stripe(female).
Fan the transducer slowly towards Right Iliac Fossa.
Fan from right, through the midline to Left Iliac Fossa assessing the pelvis for fluid collections or masses.
- Identify the symphaysis pubis on the image in transverse.
- Fan the beam slowly cephalad, identifying bladder (thick wall) and prostate (male) and vaginal stripe (female).
- Assess the suprapubic region and Pouch of Douglas (females)
The resultant image
The resultant image
A subcostal (or subxiphoid) view of the heart is obtained next. Probe grip is important –hold the transducer close to the face so that you have control over the probe and it is less likely to slip.
Change to an ‘overhand’ grip on the transducer
Subcostal pericardial probe placement.
Place the transducer in transverse position just below the xiphisternum.
Just how far below the xiphisternum the transducer is placed depends on the individual patient body habitus and the size of the transducer.
The transducer should fit between the costal margins, but not be pressing into the rib or cartilage.
1. Pressure down toward the bed is used…
2. and then the transducer is angled up towards the heart. Downward pressure on the probe is maintained.
This will result, sometimes, in the transducer being almost flat on the patients belly to obtain this view.
The transducer is angled toward the toward the patient’s left shoulder in a ‘scooping’ motion.
We are attempting to look beneath the xiphisternum and view the subcostal window to the heart.
- Optimize Image – Appropriate depth and gain settings
- If the patient is conscious, asking them to take a deep breath can assist in visualization of the heart.
- The global wall motion of the heart is observed for ‘regular’ motion.
- The pericardial space is observed for fluid. A normal amount is given as 15 – 50mls – this equates to approximately 5 mm deep pocket anterior to the Right Ventricle ( measurement provided by several websites) (4)(5). A moderate effusion is considered to be 5-10mm depth of fluid pocket. A large effusion is considered to be >10mm in size and seen anterior to the right ventricle and posterior to the left atrium iv. If cardiac tamponade is present a large pericardial effusion will be seen and the wall motion will be unsynchronized with a ‘paradoxical’ motion – the right ventricular wall will bow inwards during diastole and the Interventricular Septum will deviate towards the bowed wall.
If you cannot obtain a view of the 4 chamber heart using the subcostal view you can try to obtain an intercostal, parasternal long axis view (see below) to identify pericardial fluid or tamponade.
An intercostal, parasternal long axis view
5. PLEURA - Bilateral
To complete the extended FAST, we assess the lung for pneumothorax.
Clinical Question? Is there normal movement of the pleura between the rib spaces?
What is a positive result? The lung is not seen to slide, and there are no comet tail artifacts seen, at one intercostal space OR at all intercostal spaces.
LINEAR ARRAY PROBE
- Either a linear transducer or a curved array transducer may be used for this examination.
- The linear transducer is preferred as it is a higher frequency and the near field resolution is higher (L38), however the curved array may also be used, due to its larger near field.
- The phased array is not appropriate because of its very narrow near field.
- With the patient supine the transducer is placed Longitudinally on the anterior chest wall, at about mid-clavicular line, at the level of the clavicle
- Adjust Depth to optimize the image.
- Slide the transducer caudally pausing at each intercostal space to identify the lung edge.
- When the lung edge is visualized a sliding motion of the lung should be observed with the ‘twinkling artifact’ arising from the anterior surface should be noted. These are small comet tail artifacts, and can be described as watching a line of tiny ants crawling.
- Use of the M-Mode to document sliding motion of the lung may be of assistance. (This sliding is seen on M-Mode as the ‘sea-shore’ sign).
- Colour Power Doppler may be utilized to show the movement of the lung edge, however, if the patient is struggling to take a breath, the muscles of the chest wall may also be moving and you may get a false positive colour flash artifact.
- The transducer is moved from clavicle to lower margin of lung interrogating each rib space in turn for lung sliding and comet tail artifact.
- This is repeated on both right and left side of the chest
In the presence of a pneumothorax, you will still see the white line, representing the interface between air and the pleura – you will not see the sliding movement, or the twinkling artifacts that occur with a normal lung.
An image of each of the standard views should be documented, plus any extra images showing pathology.
As a minimum the images should be:
- Morrison’s Pouch – showing Liver,
- Kidney, Diaphragm and potential spaces.
- Splenorenal angle – showing Spleen, Kidney, Diaphragm and potential spaces.
- Pelvis Longitudinal – showing Bladder and potential spaces.
Pelvis Transverse – showing Bladder and potential spaces.
- Subxiphoid view heart – showing 4 chambers and view of pericardial space
If performing the EFAST, also consider –
6. Lung Edge at the same position on both sides of the patient or with M-Mode showing Seashore sign (if available).
7. Video Clip of sliding lung edge may also be obtained.
8. ANY ADDITIONAL IMAGES NECESSARY TO SHOW PATHOLOGY
Is the patient stable or unstable? If the patient is positive and stable – consider other sources of the fluid – is the patient on Peritoneal Dialysis? Do they have Cirrhosis? Is the patient negative and stable? Repeat the scan at regular intervals. This technique is fast and repeatable – check again to see if you missed a small collection, or if a small collection is getting larger.
Remember this examination only allows you to state whether there is fluid or not – You cannot define whether there is solid organ injury using the protocol for eFAST. This is not what the test is for. If you are querying any solid injury the patient should be transported to the X-ray Dept for CT Scan or a formal diagnostic Ultrasound.
There are decision trees available which provide suggested logical steps for patient care, however any decision made regarding treatment or further testing is at the discretion of the treating physician, using all information available. One such algorithm is provided below, (adapted from Nevit Dilmen 2011)
References and Bibliography
1. ‘POLICY ON CREDENTIALLING FOR ED ULTRASONOGRAPHY: TRAUMA EXAMINATION AND SUSPECTED AAA’ http://www.acem.org.au/media/policies_and_guidelines/P22_Credentialling_for_E D_Ultrasonography.pdf Accessed 21 January 2009
2. Leech S ‘Life-saving Point-of-Care Ultrasound Applications’ Sonosite, Inc, Sonosite Institute for Training and Education, available from www.sonosite.com
3. Bedside Ultrasonography, Trauma Evaluation http://emedicine.medscape.com/article/104363-overview accessed 22 Jan 09
4. http://www.emedicine.com/med/topic1786.htm accessed 22 Jan 09
5. http://www.webmd.com/heart-disease/guide/pericardial-effusion accessed 22 Jan 09
6. ‘Practical Applications’ Sonosite Global Learning website http://sonosite.articulateglobal.com/Portal/Workspaces
7. Goudie, A ‘Ultrasound in Trauma – foolish fad or standard of care?’ Soundeffects Issue 4 2008 pp16-18
8. Gent, R; ‘Applied Physics and Technology of Diagnostic Ultrasound’ 1997 Milner Publishing ISBN 0 646 27601 8
9. Sanders, R; Winter, T; ‘Clinical Sonography A Practical Guide’ 2006 Lippincott Williams & Wilkins ISBN-10; 0781748690