Extended Focused Assessment with Sonography for Trauma (EFAST) Exam
Hi, I'm Dr. Nadim Michael Hafez of the University of Chicago, and we're here today to discuss the focused assessment with sonography in trauma as well as the extended focus assessment with sonography in trauma. Although this exam has been in use since the early to mid '70s in Europe, it became widely used in the US in the mid to late 1990s when Dr. Grace Riziki introduced it to the US with her landmark paper. Indications for the exam broadly speaking, and based on the American College of Emergency Physicians policy statements are to rapidly evaluate the torso for evidence of traumatic free fluid or pathological error suggestive of injury in the peritoneal, pericardial, and pleural cavities. Contraindications - there are no absolute contraindications to the FAST exam or EFAST exam; however, if extensive injury to a body area precludes you from ultrasounding that area that is a relative contraindication. Also, if the patient has to go for emergent laparotomy, that would also be considered a relative contraindication. However, even in the case of emergent laparotomy, you may want to take a minute to evaluate for pneumothorax, tension pneumothorax, or pericardial tamponade, which could be treated prior to the operating room. Sensitivity and specificity.A quick review of the literature will show that the sensitivity and specificity for the Fast and EFAST exams range broadly. However, this range is also influenced by the type of trauma - blunt abdominal trauma versus penetrating trauma, the hemodynamic status of the patient, as well as the area of the body being examined - either the intra-abdominal peritoneal cavity versus the thoracic cavity versus the pericardial space. Although we will not talk about specific sensitivities and specificities as related to the FAST and EFAST exam, we will discuss general trends in sensitivity and specificity. Broadly speaking, the exam is more specific than it is sensitive. It is more sensitive in blunt abdominal trauma for evaluation of the peritoneal cavity than it is for penetrating trauma. It is more sensitive and specific in evaluation for pathology when evaluating the pericardial space and the pleural space than when evaluating the peritoneal space. It is also more sensitive and specific when the patient is hemodynamically stable versus a patient that is hemodynamically unstable. Please note - as with all ultrasound examinations, the sensitivity and specificity varies dramatically based on operator skill level, as well as patient body habitus. This video will now evaluate the five components of the EFAST examination. It will do so by covering probe selection, probe placement and image acquisition, image optimization, as well as the pitfalls and pearls associated with each window. Always remember that all ultrasound examinations require a coupling gel between the probe and the patient in order to transduce the images as ultrasound waves cannot penetrate air. In all of these windows we'll be evaluating for free fluid. Free fluid is completely black and anechoic and usually has sharp and acute angles.
The first view we'll be covering is the subxiphoid or subcostal view, which evaluates for fluid in the pericardial space.
First, we'll talk about probe selection. Probe selection should either be the phased array probe or the curvilinear probe. Both of these probes are a low frequency, thus have a long wavelength that penetrate well into the body. Whichever probe you choose, you should continue the exam with the same probe.
Probe placement. First we'll find the probe indicator. We'll take the probe indicator and align it to the patient's right. Then we'll identify the patient's xiphoid process, find the subcostal margin, place the probe right below the xiphoid process in the costal margin with the indicator to the patient's right, and then we will angle our beam directly at the patient's heart. As you can see, I've outlined roughly where Tim's heart would be. And then if you look at the screen, you can see where the heart is located on the screen. Right here, you got the right ventricle, the left ventricle, and on top you have the liver.
What we're going to do is we're going to do a quick couple of adjustments here just to optimize the picture, and that will just require adjusting the depth so that we have a full view of the heart, and adjusting the gain so that everything that's in the chamber space appears anechoic and black so that we know that we can identify free anechoic black fluid. So to orient you here, this is the patient's right as our indicator's to the right, this is the patient's left, right? This is the patient's subxiphoid or subcostal margin, and this is cephalad. The heart sits with the right ventricle angled slightly anterior and towards the probe, and the left ventricle superior and posterior. So you can clearly see liver and right ventricle, and that's the area where you're looking to identify free fluid in the pericardium.
Now we'll discuss some pitfalls and pearls of the pericardial subcostal view. Pitfall number one is failure to utilize the liver to help you view the heart. The liver is the sonographic window to the body. So if you're having trouble seeing the heart, the best thing you can do is come into the subcostal margin, come over a little bit to the right, and use that liver to visualize your heart. The second most common pitfall is the angle of the probe. A lot of novice and sonographers will start out to evaluate for the subcostal pericardial view by angling the probe too inferior. What they're doing is they're creating an acute angle between the patient's skin and the probe, and what they need to do is they need to lay it down and flatten out the probe. A great way to remember this is that your mother told you never to hold a spoon like this, but in this case, you get the hold the spoon like this because what you're trying to do is you're trying to scoop the patient's heart out. So think about angling down or lying flat and then scooping the patient's heart out, and you'll get a great view of the heart. Pearls - if you're unable to identify the subxiphoid / subcostal view for evaluation of the pericardial space by the subcostal approach, consider switching to what is known as the parasternal long approach. You can do this with, again, the curvilinear probe or with the phased array probe. Both probes will be able to do this view. And what you're going to do is you're going to take the gel from the subcostal space, you're going to find the second or third intercostal space. Parasternally on the left, you're going to place your indicator towards the patient's right shoulder and you're going to place the probe perpendicular on the patient's chest. Then you're going to come down one interspace at a time until you find cardiac activity. As you can see on the screen, we have cardiac activity, so what we're going to do now is we're going to adjust the depth to optimize our image. And what we want is you want this circle down here, this black circle, which is the descending thoracic aorta, to be the last thing that we have in view, you'll see the left atrium, the mitral valve, the left ventricle, the left ventricular outflow tract, the aortic valve, the ascending aorta, and the right ventricle. In this view, free fluid, or pericardial fluid, is located at the bottom of the picture. As in this case, you can tell that this is the top of the patient, or anterior, and this is deep and posterior. So by gravity fluid would become posterior and it should layer out back here. Things to remember about this view that's very important is that even though fluid is present, that fluid may not be causing tamponade or obstructive shock, so you need to evaluate for right ventricular collapse during diastole, which is the sign that we're looking for to evaluate and find tamponade and obstructive shock.
We'll now discuss the right upper quadrant view of the EFAST examination.
Probe selection for this view could either be the curvilinear or the phased array probe. Both of these probes have low frequencies and long wavelengths, allowing them to penetrate deep into the body.
Probe placement and image acquisition. We're going to take the probe and we're going to take the indicator on the probe, and we're going to align that indicator with the patient's head. So the indicator on the probe is going to be facing towards the patient's head. We're going to identify the anterior axillary line on Tim, the posterior axillary line, and the midaxillary line. We'll start the exam in the 8th through 11th rib space, right about the level of xiphoid and the midaxillary line. So I'm going to place my probe there - a little cold gel. And then we're going to aim posteriorly at the spine. And what we're looking for is what we found on the screen. We're looking for the patient's kidney and the liver. The interface between the kidney and the liver is a potential space known as Morison's pouch. There is no actual pouch, the kidney is retroperitoneal, and the liver is intraperitoneal. So the liver, when the patient's supine, is lying on that posterior peritoneal reflection that the kidney has made from the retroperitoneum into the peritoneum. What happens is if we put fluid into his peritoneum, the liver just lifts off of the kidney. There is no attachment between the kidney and the liver in the right upper quadrant, or hepatorenal view. Some structures that we can see here are the kidney, the liver, and the diaphragm, as well as these white bumps that represent Tim's spine.
Image optimization. We'll talk about image optimization of the right upper quadrant view. In order to optimize this image, we're going to properly set our depth and gain. So what we're going to do is we're going to adjust this so that the bottom of the image is the spine, and that we're able to see diaphragm, and that we're able to see both the kidney, and that we're going to be able to see the liver as well. While evaluating the right upper quadrant for free fluid, what we're looking for is again anechoic black fluid that shows up with acute angles, and what we're looking for is we're going to look for it between the kidney and the liver. The other space that we're evaluating here is the hemithorax. Tim, take a deep breath in. As he takes a deep breath in, you can see the diaphragm move inferiorly. So just to reorient you, this is the patient's head, this is the patient's foot, this is the patient's right side, and this is down and towards the left. So as Tim takes a breath, you'll see his lungs inflate.And what happens is because air cannot penetrate - or ultrasound cannot penetrate air - go ahead and exhale. There is a loss of the picture. So go ahead - inhale - we can see less, and then when he exhales, we can see more. Right? Because we cannot image through the lung. Now, as you can tell, you have the white line of the diaphragm there, and it looks like there's gray liver above and below the diaphragm. We know there's no liver above. This is caused by something known as a mirror image artifact. This artifact is a normal artifact. All imaging of the lung is usually either the presence or the absence of an artifact. The artifact can be normal, as in this mirror image artifact, or the artifact can be abnormal and represent pathology.So we're able to see if there is trauma to the hemithorax; if there is a hemothorax, we should be able to see a black area of fluid behind the diaphragm. Because that black fluid allows us to image further into the body regardless of how deep he takes a breath, we'll be able to see the spinal bumps continue off the screen. That's called a spine sign. So a positive spine sign would represent fluid in the hemithorax - in case of trauma, a hemothorax. Go ahead and take a deep breath. And the mirror image artifact itself - go ahead and exhale - which shows liver above and below this curved white line, which is the diaphragm is normal and rules out fluid in the hemithoraces.
We'll now discuss pitfalls and pearls of the right upper quadrant view of the EFAST examination. Pitfall number one - most novice sonographers will angle the transducer too horizontally and forget to lift up and aim down and towards the spine. By aiming horizontally, they're able to see the inferior vena cava and the liver but are unable to find the border between the kidney and the liver, or Morison's pouch. Pitfall number two - most novice sonographers place the transducer on the anterior axillary line instead of the posterior axillary line. What happens then is that you have to image through bowel, as you see here, and then you get gas shadow so you're able to not see the real interface between the kidney and the liver, or Morison's pouch, because you started too high on the body. Pitfall number three is acquiring a view of Morison's pouch without scanning through the inferior tip of the liver. This is the patient's head, this is the patient's foot, this is the patient's right side, and this is down and to the left. Fluid will collect on the inferior tip around the liver's inferior tip before it collects in Morison's pouch. So if you have this view, you might be missing fluid up here. In order to get past that what you're going to do is you're going to take your hand and you're going to rock the probe down towards the patient's foot. That's basically just turning along the curvature of the probe and aiming the beams towards the patient's feet. You're going to find the inferior triangular tip of that liver and then you're going to scan through it. What you're looking for, again, is free anechoic black fluid, which would represent blood in the case of a traumatic injury.The last pitfall we'll discuss is mistaking edge artifact for free fluid. When evaluating the right upper quadrant view of Morrison's pouch, it can often be a minimal black shadow that appears between the kidney and the liver edge. This usually appears somewhere along this area. If you notice though, if I go and look at the inferior liver edge, and I fan through that liver edge, there is no fluid around there. Any fluid that is to the left on the screen, or the patient's head in this case, right? This is his head, and this his foot, but does not pool around the liver edge cannot be free fluid. By gravity, free fluid has to collect in the most gravitational dependent area, which is around this liver tip. So if you find any kind of black anechoic stripe here, but then when you go down by rocking the probe and fanning around the liver edge, if you don't see that, that cannot be free fluid. One pearl is to take your indicator on your probe and instead of just angling it to the head is to rotate it and align it with the ribs. As you can tell we're getting rib shadow from the top of the screen, but if I take the transducer indicator, and instead of just aiming it straight up, I aim it towards the actual bed, I'm able to go in between the ribs and eliminate these shadows. Pearl number two for the right upper quadrant. Once evaluating the right upper quadrant, if you have trouble finding the diaphragm, slide your transducer up and down on the patient's body until you've optimized the image and got a good mirror image artifact, or lack thereof, or positive spine sign to evaluate the hemithorax.
We'll now discuss the left upper quadrant view of the EFAST examination.
Probe selection for the left upper quadrant view of the FAST exam include the phased array probe or the curvilinear probe. Again, both probes have a low frequency, long wavelength, and thus penetrate deep into the body. Whichever probe you choose, continue the rest of the examination with the same probe.
Probe placement and image acquisition for the left upper quadrant. First, identify the patient's left anterior axillary line, midaxillary line, and posterior axillary line. In the left posterior axillary line between the 7th and 10th intercostal space, place the probe with the indicator towards the patient's head. You'll obtain an image of the left kidney and the spleen, or the splenorenal left upper quadrant view. We're looking for black anechoic fluid between the spleen and the kidney.
Image optimization for the left upper quadrant. Once you've obtained a view of the left upper quadrant, make sure to adjust both depth and gain in order to optimize the image. So what you're going to do is you're going to want to have the kidney and the spleen in view, and then hopefully be able to see the bumps of the spine and the diaphragm as well. And make sure to adjust your gain accordingly. While imaging the left upper quadrant, it's important to remember that the spleen and the left kidney are anchored by the splenorenal ligament. That means that when fluid accumulates between both the spleen and the kidney, it will not separate the spleen completely from the kidney, as it does in the right upper quadrant. In the right upper quadrant, the retroperitoneal kidney and the intraperitoneal liver are not anchored as the spleen and the kidney are here. Fluid will accumulate around the inferior border of the spleen, and it will track in this direction superiorly towards the diaphragm.
Pitfalls and pearls. Common pitfalls of the left upper quadrant include failure to place the transducer on the posterior axillary line. Most novice [sonographers] will start with the transducer too high in the midaxillary line, allowing them to visualize the spleen but not allowing them to visualize the kidney and the spleen. Another pitfall of the left upper quadrant view is that the novice sonographer fails to realize that the kidney and the spleen are anchored. They'll obtain a view such as this where you can see kidney and spleen but not see the inferior tip of the spleen. Pearls for the left upper quadrant view of the FAST exam. Probably the easiest one is probe positioning. Take your thumb, place it on the underside of the probe, and your index finger at the top. Now rotate your hand around. Place your knuckles in the stretcher of the bed and place the probe with the indicator towards the patient's head in the posterior axillary line. This aligns the probe from posterior to anterior angled towards the spine, allowing you to find the paraspinal kidney. Once you've had correct probe placement and you've found an image that resembles this image up here with kidney and spleen, go ahead and slide superior and inferior on the patient in order to optimize your view. This is a good view as it shows the inferior tip of the spleen where fluid collects first and it shows the diaphragm as well as a spine, allowing us to view the left side mirror Image, which is spleen on both sides of the diaphragm. As with the right upper quadrant, you can evaluate the left upper quadrant to see fluid in the hemithoraces, so to look for a hemothorax on the left, we would again look for the spine to continue off the screen here, instead of having the spine stop at the diaphragm, and seeing spleen on both sides of the diaphragm.
We'll now discuss the suprapubic view of the EFAST exam.
Probe selection for the suprapubic of the EFAST exam include the phased array and curvilinear probes. Both probes are low frequency, long wavelength and allow you to penetrate deep into the body.
Probe placement for the pelvic view of the FAST exam is to take the probe with the indicator towards the patient's right in the suprapubic area perpendicular to the patient's abdominal wall. You will then tilt the probe, or fan it, down into the pelvis. We'll get a view of his bladder. Tim's pelvic view shows his bladder and his prostate. You're going to first fan through the bladder and prostate in the transverse axial plane with the indicator to the patient's right. Next you'll rotate 90 degrees, putting the indicator towards the patient's head for a sagittal longitudinal view, and you will fan from left to right, or right to left, in order to gain an entire view of the pelvis. Again, you're looking for anechoic black fluid, which would have sharp acute angles.
Image optimization. Remember that once you've acquired the image, you want to make sure you adjust the image to have the proper depth. In this case, you want to be able to see bladder, prostate, and the pelvis beyond both structures. And then make sure you adjust the gain to allow you to view anechoic black urine as well as possible free anechoic black fluid.
Pitfalls and pearls. A common pitfall to the pelvic view is to start the examination in an infraumbilical location rather than a suprapubic location. This is too high and requires you to look through bowel gas, which will scatter your beams and not allow you to see the bladder and thus the pelvis. You're using the bladder as a window to view the pelvis. If you start too high, you will not be able to catch the bladder and not be able to view the pelvis. A second pitfall is to fail to remember that fluid accumulates in different areas in both a male and female pelvis. In Tim's pelvis, as we take a look, we see the bladder and then the prostate. Fluid will accumulate behind the bladder between the bladder and the prostate. In a female pelvis, you'll have the bladder, if they haven't had a hysterectomy the uterus, and then the bowel. And fluid will accumulate behind the uterus in the rectouterine pouch of Douglas. Another pitfall is to forget that fluid that we're looking for is free fluid, which is black anechoic, much like the urine, but it has sharp angles. Oftentimes, these dark spaces, which are really bowel and gas, as there's a hyperechoic area, and then a grayish, blackish shadow is mistaken for free fluid. Remember that gas lets you see less and fluid lets you see more. So if I were to fill Tim's pelvis up with fluid, I would be able to see more rather than less. It would outline all of his bowel, it would outline his bladder, his prostate, and his rectum. So I'd be able to see all of the parts more clearly. If you don't see anything, and it looks black that doesn't necessarily indicate that there's free fluid, as much as it more indicates that there's likely to be gas. Free fluid shows you more rather than less. Pearls of the pelvic view. When evaluating the pelvis, you'll notice that the area behind the bladder is brighter than the adjacent areas. This is due to an artifact known as posterior acoustic enhancement. Any fluid-filled structure shows the area behind it to be brighter because the beams that went through the fluid-filled structure come back stronger and thus are interpreted as brighter by the ultrasound machine. This is an artifact that can be compensated for by using your time gain compensation. Just turn the gain and the backfield down, and you're able to identify free fluid more easily.
We'll now discuss the pleural view of the FAST exam, which evaluates for the presence or absence of a pneumothorax. Specifically, what we're looking for is a tension pneumothorax.
Probe selection for the pleural view can either be the linear high frequency probe, the phased array probe, or the curvilinear probe. Remember that when using the phased array and curvilinear probe, you'll have to decrease the depth in order to view the pleural line. And when using the linear probe, you're going to have to switch to either the curvilinear or the phased array probe for the remainder of the exam.
Probe placement for the pleural view of the FAST exam is the 2nd to 3rd intercostal space. The indicator is placed towards the patient's head. We'll get an image of such. We'll identify your rib with its corresponding shadow. And we'll try to put two ribs on the screen and find the pleural space beneath it and see the pleural line, which is going back and forth. This is the visceral and parietal pleura as they are opposed to each other with a small amount of fluid in between that we can't see. And when Tim takes a deep breath, we can see the line going horizontally back and forth. As we would see with normal pleural sliding. What we're looking for here is either the absence of this sliding, which would indicate the possibility of air between the visceral and parietal pleura, or sliding to a certain point, which would be known as a lung point, which is the point at which the collapsed lung is entering our view, and then leaving our view every time the patient takes a breath in and out. An adjunct to using either the linear, or curvilinear, or phased array probe when evaluating the pleural spaces, is to use M mode. M mode is motion over time. It takes a sample line and displays motion in a vertical direction over time in a horizontal direction. We can see our pleural line is about 1.5 cm down. So at 1.5 cm, everything above is linear, and everything below is slightly grainy. And that has to do with the fact that you cannot image lung. You can only see the presence or absence of an artifact as we discussed. Right as Tim takes a breath, it is normal to have linear on top and grainy on the bottom. That is called the seashore sign. If Tim had a pneumothorax, what I'd expect to see is I'd expect to see a barcode sign. So everything would look kind of linear like it does at just the top of the screen.
Image optimization for the pleural view revolves mostly around either using M mode or making sure you adjust the depth on the curvilinear and phased array probes in order to clearly visualize the pleural line.
Pitfalls and pearls. Pitfall number one is failure to adjust the depth on either the curvilinear or phased array probe. If you take a look at his pleural space with a curvilinear probe, you'll notice immediately that the preset depth for a FAST exam places you at about 15 cm. The pleural line is rather small and the motion is not very visible. Decreasing the depth in order to increase visibility of the pleural line is necessary, as you would fail to recognize lung sliding otherwise. Pitfall number two on the pleural view of the EFAST examination is failure to use M mode to evaluate for a pneumothorax. Pitfall number three is failure to realize that while using the M mode to identify lung sliding in a patient that has been intubated that there may be absence of lung sliding on the left hemithorax due to a mainstem intubation. If you mainstem intubate the patient, you're only ventilating the right hemithorax, and thus there's no movement of the pleural line on the left. And that would lead you to believe that the left lung is collapsed and may make you falsely place a chest tube on the left. What you're looking for in that case is a lung point, which would be an area where you have lung sliding in only one point in the M mode. So the M mode picture would look like a barcode sign everywhere, so everything would look very linear. And then we'd have a tower or strip of beach that would come up every once in a while, when the lung that is collapsed inflates to the point of being in the M mode view and then out of the M mode view. Pearls for the pleural view of the EFAST examination are to use M mode. M mode can be very helpful in identifying pleural movement, the absence of pleural movement, a lung point, or a barcode sign. A lung point is the most sensitive and specific thing for pneumothorax as it can help on both the left and the right side in order to evaluate for a pneumothorax. The absence of lung siding on the left as previously mentioned, does not rule in a pneumothorax. Pearl number two for the pleural view is to remember to move the probe up and down on the patient. Start in the 2nd intercostal space and scan from 2nd to 4th, and back to 2nd to see if you can find a large pneumothorax.