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Extended Focused Assessment with Sonography for Trauma (EFAST) Exam

Abstract

This video-article covers pertinent information related to the focused assessment with sonography for trauma exam, which evaluates the pericardial, hepatorenal, splenorenal, and suprapubic regions for free fluid in a trauma patient. It also covers additional information regarding the extended focused assessment with sonography for trauma (EFAST) exam, which includes an additional evaluation of the pleural spaces for a pneumothorax. 

Case Overview

The focused assessment with sonography for trauma (FAST) exam has been used since the 1970s but became prevalent in the United States in the 1990s after a landmark paper by Dr. Grace Rozycki.1 Performing an extended focused assessment with sonography for trauma (EFAST) exam has become standard practice in the initial evaluation of a trauma patient.2 Many studies have proven that an EFAST exam is a helpful tool for elucidating the presence of free intraperitoneal fluid,3,4 a pericardial effusion, and a pneumothorax.5,6 The exam has been part of the Advanced Trauma Life Support (ATLS) algorithmic approach to the treatment of trauma patients set forth by the American College of Surgeons since the late 1990s (ACS).7

A) Beginning the Exam

To begin, all exams require a coupling gel to be applied between the probe and the patient in order to obtain the images. This is because ultrasound waves cannot penetrate air.8 Free fluid is usually completely anechoic (black in color) on imaging and has sharp and acute angular edges.8 For probe selection, either the phased array or the curvilinear probe is used for all views of the EFAST exam.2,9 These probes are low frequency/long-wavelength probes and can penetrate deep into the body.8 Regardless of which probe is chosen, it is usually best to complete the entire exam with this probe in order to save time. However, the pleural exam will require reducing the imaging depth dramatically on both probes, which in turn may lead to poorer resolution and increased difficulty identifying a pneumothorax. In this case, it may be necessary to switch to the high frequency/short wavelength linear probe in order to detect a pneumothorax.2,10,11

B) Subxiphoid/Subcostal or Parasternal Long View for Pericardial Space
B.1) Subxiphoid/Subcostal View

The subxiphoid view evaluates for free fluid in the pericardial space. Place the probe indicator towards the patient’s right side.10 Find the xiphoid process and place the probe below it at the right subcostal margin. Angle the ultrasound beams superior and towards the patient’s left shoulder directly at the heart.9,10 To optimize the picture, adjust the depth and gain.12 The left of the screen correlates with the patient’s right side, and the right side of the screen correlates with the patient’s left side. The top of the screen correlates with tissues that are directly inferior to the xiphoid process/right costal margin (i.e. liver), and the bottom of the screen correlates with those tissues that are cephalad. Look at the intersection between the liver and the right ventricle to determine if the free fluid is present.9 If there is trouble viewing the heart, attempt to increase your use of the liver to visualize the heart by sliding the probe towards the patient's right inferior costal margin, while still maintaining the same orientation noted above.2 Make sure the angle between the bottom of the probe and the anterior abdominal wall of the patient is not too acute. The probe in most cases should be completely flattened and resting on the anterior abdominal wall to be able to view the heart clearly.9 If the heart cannot be visualized via the subxiphoid view in a timely manner (30 seconds to one minute) move on to the parasternal long cardiac view.2,10 

B.2) Parasternal Long View

Find the 2nd/3rd intercostal space parasternally on the patient’s left side. Place the indicator towards the patient’s right shoulder and place the probe perpendicularly on the chest wall.10 Come down one interspace at a time until the cardiac activity is visualized.10 Once visualized, adjust the depth to have the descending aorta at the bottom of the image. In this view, pericardial fluid is located at the bottom of the image, which correlates to the most gravitationally dependent area of the pericardium. Remember that pericardial fluid may be present but not be causing pericardial tamponade. It is important to assess for right ventricular collapse during diastole, which is sonographic evidence of cardiac tamponade, a type of obstructive shock.2,9,13 The pericardial view on the FAST exam can detect as little as 20 cc of pericardial fluid.14 Keep in mind that the rate of accumulation, not the amount of fluid, is the determining factor for a patient going into obstructive shock. 

C) Right Upper Quadrant View/Hepatorenal View

Align the probe indicator towards the patient’s head. Find the anterior axillary, midaxillary, and posterior axillary lines. Start the exam at the midaxillary line at the level of the xiphoid process, approximately between the 8th and 11th rib spaces.2,9 Aim the probe posteriorly at the spine. Look for the interface between the kidney and liver. This is a potential space, known as Morrison’s pouch. Ultrasound may be able to detect as little as 200 ml of fluid in this space.15 If there is fluid present in the peritoneum, the liver lifts off the kidney, and anechoic (black) fluid appears at this interface.10 The kidney, liver, diaphragm, and spine are visualized in this hepatorenal view. To optimize the image, set depth and gain so that the spine is at the bottom of the image. Look also at the hemithorax for free fluid.10 The diaphragm will move inferiorly with inhalation, and because ultrasound cannot penetrate air, fewer of the vertebrae of the spine will be visible with deep inspiration. A mirror image artifact is present when it appears as though the liver is visible cephalad and caudal to the diaphragm. A mirror image artifact is normal and rules out fluid in the hemithorax.9 Lack of mirror image artifact in the lung represents pathology such as hemothorax or pleural effusion.9 A black anechoic area of fluid will show up behind the diaphragm.15 This fluid will allow visualization of the vertebrae superior to the diaphragm at the bottom of the image. This is known as a positive “spine sign”.15 In a trauma patient, this represents a hemothorax.2 

One pitfall is angling the transducer too horizontally instead of aiming the ultrasound beams posteriorly, down towards the spine. The second pitfall is placing the transducer on the anterior axillary line instead of the posterior axillary line. Placing the probe on the anterior axillary line will limit the ability to visualize the intraperitoneal structures as the ultrasound beams may be scattered by bowel gas. The third pitfall is not scanning through the inferior tip of the liver. This is the first place where fluid collects, and thus the most sensitive area of the hepatorenal view to detect free fluid.2,10,16 The last pitfall is mistaking edge artifact for free fluid. There can often be a minimal black shadow that appears between the kidney and liver edges. Free fluid has to collect in the most gravitationally dependent area, which is the above mentioned inferior tip of the liver.2,10,16 One pearl is to rock your probe inferiorly to increase visualization of the inferior liver tip. After you have visualized the tip you should fan through it in order to evaluate for any traces of free fluid. A second pearl is to angle the probe indicator towards the bed and angle your probe between the patient’s ribs in order to avoid any shadows they may cast onto the screen.2 

D) Left Upper Quadrant View/Splenorenal View

Align the probe indicator towards the patient’s head. Find the left anterior axillary, midaxillary, and posterior axillary line. Start the exam at the posterior axillary line at or slightly above the level of the xiphoid process 2,10 approximately between the 7th and 10th rib. Place your thumb on the underside of the probe, index finger on top of the probe. Reaching across the patient, firmly place the knuckles of the hand holding the probe onto the stretcher.10 This will angle the probe slightly anteriorly towards the patient's spine. Obtain a view of the left kidney, the spleen, and the left hemidiaphragm. You are looking for black, anechoic fluid between the spleen and the kidney.9,10

For image optimization, adjust depth and gain.12 Try to visualize the spleen, left kidney, vertebrae, and diaphragm in one view. It is important to remember that the spleen and left kidney are anchored by the splenorenal ligament. This means that if fluid accumulates between the spleen and left kidney, it will not separate the left kidney completely from the spleen the way the right kidney separates from the liver.10 Fluid will typically accumulate around the inferior border of the spleen and it will track superiorly towards the diaphragm.

One pitfall is the failure to place the transducer on the posterior axillary line; most novice users place the probe on the midaxillary line. The left kidney is more superior and posterior in its location when compared with the right.2,10 Another pitfall is failing to realize that the spleen/left kidney is anchored, thus obtaining an image of the interface between the two organs but not the inferior tip of the spleen.

Pearls for left upper quadrant imaging emphasize probe positioning. Once the spleen, left kidney, and diaphragm are in view, slide or rock the probe superiorly and inferiorly to optimize the view. It is important to find the above mentioned inferior tip of the spleen. Fan through the inferior spleen tip in order to find any traces of free fluid.10 Additionally, don’t forget to check for the presence of a spine sign on the patient’s left.15,17

E) Suprapubic View

Place the probe in the suprapubic region, just superior to the pubic symphysis, with the indicator towards the patient’s right side.2 In this transverse/axial plane with the probe perpendicular to the skin, fan the probe cephalad and caudal through the patient's pelvis).10 In a male patient, free fluid should be found behind the bladder. In female patients, free fluid is found behind the uterus anterior to the rectum within the rectouterine pouch (i.e. Pouch of Douglas).2,10,18 Remember to fan the probe superiorly and inferiorly to scan the entire pelvis.9,10 Once complete, rotate the probe 90 degrees with the indicator towards the patient’s head to obtain a sagittal/longitudinal plane.2,17 Again fan the probe, this time from right to left to scan through the entire pelvis.10 You are looking for black, anechoic fluid, which should have sharp/acute angles. For image optimization, adjust the depth so you can see the bladder, prostate (male), uterus (female), and space just deep to these organs.

One common pitfall is placing the probe infraumbilical instead of suprapubic. If the probe is too high, bowel gas interferes with imaging.2 Another pitfall is failing to realize that pelvic free fluid accumulates in different places for men and women as mentioned above. Failing to recall that free fluid is anechoic with acute angles15 and that it allows the sonographer to identify additional structures otherwise hidden by bowel gas is an additional pitfall. It is easier to visualize an image when the ultrasound waves are traveling through fluid; it is impossible to do so when they are going through gas/air.2 One pearl is to compensate for the posterior acoustic enhancement (PAE) artifact caused by the bladder with time gain compensation. PAE artificially increases the gain of any tissues that lie just beyond a fluid-filled structure (e.g., bladder). This artificial increase could cause the sonographer to miss free anechoic black fluid. Turning down the gain beyond the bladder (shifting grayscale towards the anechoic end of the spectrum) allows the sonographer to better visualize anechoic free fluid in the pelvis.  

F) Pleural View

This view can be obtained using either the linear (high frequency), phased array (low frequency), or curvilinear (low frequency) probes.11 If using the phased array or curvilinear probes, be sure to decrease the depth to better visualize the pleural line. Place the probe between 2nd and 3rd intercostal spaces along the midclavicular line with the indicator towards the patient’s head.2,9,10,11 Identify two ribs, their accompanying shadows, and the pleural line between them on the screen. The pleural line represents the opposed visceral and parietal pleurae.8 Depending on the presence or absence of various sonographic artifacts (e.g., comet-tail artifacts, lung sliding, A-lines, B-lines, lung point sign), the examiner is able to diagnose a variety of lung pathologies (e.g., pneumothorax).9,11 When a patient with healthy lungs takes a breath, horizontal “sliding” along this line represents a normal movement.8,15 Often “comet tail artifacts” are also seen.11 If sliding is not visualized, a pneumothorax may be present.8,10 M mode, which represents motion over time, is a useful adjunct for visualizing lung sliding. It samples motion along one area (designated line) on the screen. The motion detected is represented on the vertical (y) axis across time, the horizontal (x) axis, on the M mode graph. In a patient with normal lung sliding on M mode, everything above the pleural line appears linear (representing absence of movement). Everything below the pleural line is grainy. This is called the “seashore sign”.9,10 If a patient has a pneumothorax, you would expect to see only horizontal lines, also known as the “barcode” or “stratosphere” sign, due to the absence of pleural movement.2,10,11 A highly specific ultrasound sign for a pneumothorax is the “lung point”, which visualizes the point where the visceral pleura (lung) begins to separate from the parietal pleura (chest wall) at the edge of a pneumothorax.2,11,19 When the examiner places the probe at the “lung point” while using M mode, you would see alternating “seashore” and “barcode” signs as the patient inhales and exhales.8 The position of the lung point depends on the size of the pneumothorax.11,19

For image optimization, adjust the depth to adequately see the pleural line. This is especially important for the phased array and curvilinear probes. Failing to do so is a common pitfall. A second pitfall is failing to use M mode to help identify the presence of either a seashore sign or a lung point.2 A third pitfall is failing to realize that absence of lung sliding or “barcode sign” with M mode when visualizing left hemothorax in an intubated patient may represent a right mainstem intubation instead of a pneumothorax.9,11,20 Try to identify a “lung point” on the left side if there is a concern for a possible pneumothorax on this side. One pearl is to scan superiorly and inferiorly between the 2nd and 4th intercostal spaces to look for a large pneumothorax.

Discussion

The indications for this exam, based on the American College of Emergency Physicians' policy statement, are to rapidly evaluate the torso for evidence of traumatic free intraperitoneal fluid or pathologic air suggestive of injury in the following cavities: peritoneal, pericardial, and pleural.15,21 There are no absolute contraindications to the FAST/EFAST examination.2 However, certain instances may preclude the exam, such as severely damaged tissues/open wounds or the need for immediate operative intervention.21 Yet, even when a patient is going to the OR for emergent laparotomy, it is still acceptable to take time to evaluate for other life-threatening emergencies including tension pneumothorax or pericardial tamponade that could be treated prior to going to the operating room. 

The sensitivity and specificity of the FAST and EFAST exams range broadly. For instance, one meta-analysis systematically reviewed studies on penetrating and blunt trauma and found the pooled sensitivities and specificities of the EFAST exam to be 69% and 99% for detecting pneumothorax, 91% and 94% for pericardial effusion, and 74% and 98% for intra-abdominal free fluid, respectively.5 These numbers are influenced by many factors including blunt vs penetrating abdominal trauma,9 hemodynamic status, and the area of the body being examined. Broadly speaking, the exam is more specific than it is sensitive.5 Thus, a negative FAST exam does not rule out traumatic injury.10 For example, up to 29% of patients with a negative FAST exam still have intra-abdominal injuries.22,23 It is more sensitive in blunt abdominal trauma than penetrating trauma. For blunt abdominal trauma, sensitivities generally range from 73–99% for detecting free intraperitoneal fluid.3,8,24 The specificity of the FAST exam for both blunt and penetrating abdominal trauma is 94–100%.8,25 It is more sensitive than specific when evaluating pathology in the pleural and pericardial spaces compared with the peritoneal space.26,27 EFAST is also more sensitive for detecting pneumothoraces compared with chest radiographs.2,8,11,15,28,29,30 Supine chest radiographs performed during ATLS have a range of sensitivities between 28–75% for detecting traumatic pneumothorax, compared with the EFAST exam, which has a higher sensitivity of 86–97%.31 One study found the sensitivity and specificity for detecting hemothorax in blunt thoracic trauma patients to be 92% and 100%, respectively.32 To visualize hemothoraces, supine or upright chest X-rays require up to 50–175 ml of fluid, compared with the EFAST exam, which can detect as little as 20 ml of fluid in the pleural space.33 A highly specific ultrasound finding for a pneumothorax is the lung point, which boasts a sensitivity of 59–75% and specificity of 99–100%.7,18 Ultrasound can also detect as little as 20 ml of pericardial fluid in a penetrating chest trauma patient.14 The sensitivity and specificity also vary with the skill level of the operator and the patient’s body habitus.2,15, 26, 34

Equipment 

Bedside ultrasound 

A phased array (or cardiac) probe or a curvilinear (or abdominal) probe 

Disclosures

Nothing to disclose.

Statement of Consent

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.

Citations

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