We’re back! Last time we reviewed eFAST basics and part of the eFAST technique. Hopefully you’ve been practicing the heart, RUQ, and LUQ scans like my friend below. So without further adieu…. I give you eFAST Part Deux!
How to Do I Do an eFAST? (Continued from Part 1)
- Probe marker towards patient’s head (longitudinal view) or towards patient’s right (transverse view)
- Place the probe just above the pubic symphysis and look for the bladder in men and both the bladder and uterus in women
- If it doesn’t feel a little awkward, you’re not low enough
- Once you’ve finished the longitudinal view, turn the probe 90° to get the transverse view. Both views should be evaluated to avoid false positives
- Scan through the entire bladder
- Be sure your probe is perpendicular to the patient when scanning. Do not crank the probe to extreme angles to find the bladder.
- If you’re not seeing bladder with the probe perpendicular to the patient, slide it down or up in a plane parallel to the patient. This is important to avoid false positives or false negatives to due changing the angle of the pelvis image.
The image (in men):
- Find the bladder. The rectovesicular pouch (between rectum and bladder) is immediately posterior to the bladder.
- Now find the prostate (inferior to the bladder) and scan towards the patient’s head until it disappears. This marks the beginning of the rectovesicular pouch.
- The prostate is an extra-peritoneal organ. It marks the inferior end of the rectovesicular pouch.
- Scan the rectovesicular space until the bladder disappears
The image (in women)
- Find the uterus (posterior to the bladder). The pouch of Douglas (rectouterine pouch) is immediately behind it.
- Scan the pouch of Douglas until the uterus and bladder disappear
- A positive exam has free fluid
- In both men and women this is the 1st place blood collects in the lower abdomen
- In men: look for free fluid in the rectovesicular pouch (behind the bladder)
- In women: look for free fluid in the pouch of Douglas
- Be aware of the possibility of false positives if your probe angle is too steep in the transverse plane
- When your probe angle is too steep, you change the viewing plane so that images that appear posterior to the bladder on the screen are actually more inferior and extraperitoneal. This means you’re imaging more inferior structures (like seminal vesicles, which contain fluid… can we say false positive) and missing the peritoneal space you should be evaluating.
Video Links (courtesy of sonocloud.org)
Probe selection and position:
- Ideally, select a linear probe (high freqeuency) for best image quality
- If you’re in a hurry (like in an unstable trauma), a phased array or curvilinear probe is fine
- Orient the probe marker towards the patient’s head
- Place the probe over the 3rd and 4th intercostal space
- Right side: at the midclavicular line
- Left side: at the anterior axillary line (Remember the heart? It’s kind of in the way at the left midclavicular line)
- Slide the probe along the chest longitudinally
- You’ll see ribs and the space between them
- Directly underneath the ribs is the pleural line
- To evaluate the pleural line in a specific location, anchor your probe before you evaluate the image
- You can also use M mode (it’s a button on the ultrasound machine) to evaluate for pneumothorax
- You’re looking at the pleural line for signs of a pneumothorax
- A normal pleural line shimmers or looks like “ants marching in a line”
- This is due to sliding of the pleura over one another during breathing
- Normal sliding means there is no air in the pleural space and excludes a pneumothorax
- A “dead line”, no movement, suggests a pneumothorax
- The chest wall will still move, so don’t be tricked into thinking chest wall movement is pleural line movement
- M mode images are an easy way to look for pneumothorax
- Seashore sign: lines of the chest wall followed by granularity below the pleural line, means no pneumothorax present
- Barcode sign: nothing but lines for the whole image, means there’s a pneumothorax
- B-lines (comet tails): looks like little rays of white shooting down from the pleural line
- This is ONLY seen with intact pleura
- If you see this, there is no pneumothorax!
And you already evaluated for hemothorax when you looked above the diaphragm in the liver and spleen views, so you’re done with the eFAST!!
Video Links (courtesy of sonocloud.org)
Discussion of Relevant Anatomy: The Brains Behind an eFAST (Continued from Part 1)
In the pelvic view, anatomy is exceptionally relevant to understanding an eFAST exam. The borders of the peritoneal and pelvic compartment meet here. It’s important to know where the compartment boundaries are, so you can identify which compartment free fluid originated from. The pelvis is also an important dependent area. This is a hot spot for finding free fluid, so pay attention to the pelvis.
In men, you are looking for free fluid in the rectovesicular pouch. This is between the rectum and bladder. Both of these are extra-peritoneal structures, but they are draped in peritoneum superiorly and along the surfaces between them. The space between them is in the peritoneal cavity, so any fluid in the rectovesicular pouch is intra-abdominal free fluid. The inferior border of the rectovesicular pouch can be identified by the prostate, which is an extraperitoneal structure just inferior to the bladder and adjacent to the inferior border of the rectovesicular pouch. Another extraperitoneal structure to consider are the seminal vesicles, which are posterior to the inferior portion of the bladder and inferior to the rectovesicular space. Since seminal vesicles contain fluid, this fluid could be falsely identified as intra-peritoneal with improper probe positioning. Seeing seminal vesicles like this is uncommon, but definitely possible. More common would be an extraperitoneal bladder rupture that you could diagnose this way, which would be treated differently than an intraperitoneal rupture.
It’s important to know if you’re extraperitoneal vs. intraperitoneal. This is why keeping the probe perpendicular to the patient is so important. If you mistakenly cranked the probe in the transverse view and imaged the bladder at an angle, images that appear posterior to the bladder on your screen would actually be more inferior (see figure 13 below). This would reveal extraperitoneal structures instead of the peritoneum. It’s an easy enough mistake, so be aware of it
Scanning in two planes (longitudinal and transverse) also minimizes false positives and false negatives, since the longitudinal view can help determine whether fluid is more superior in the rectovesicular pouch or more inferior in an extraperitoneal structure. So basically, in men scan the entire bladder to visualize the entire rectovesicular space and be aware of your probe angle, so you don’t mistake extraperitoneal fluid for intra-abdominal fluid (a false positive) or miss intra-abdominal fluid (a false negative). Now for the ladies.
In women, you are looking for free fluid in the pouch of Douglas, the space between the uterus and the rectum. When you’re scanning the pelvis, you’ll see bladder most anteriorly, then uterus, and finally rectum. The uterus and rectum have the same peritoneal cover as in men, so the pouch of Douglas is in the peritoneum and free fluid found in it originated from the abdomen. And that’s it for pelvic anatomy.
The last scan is the lungs. Here you’re checking for pneumothorax using features of the pleural line and other chest anatomy. The visceral and parietal pleura come together with a little bit of fluid to hold them together just below the ribs. If the pleura are sliding over one another, no pneumothorax is present. A sliding pleural line looks shimmery or like “ants marching in a line.” Be sure to hold your probe still when evaluating the pleural line, so there’s no illusion of movement caused by a shifting image on the screen. If there is no sliding, you’ll still see a pleural line from the parietal pleura. It just won’t be shimmery or move.
Another feature of intact pleura are B-lines. These look like comet tails radiating down from the pleural line into the lung. They’re caused by fluid and air interfaces distorting the sound waves. If there’s fluid, there’s no pneumothorax. So B-lines rule out pneumothorax! And since air tends to rise, duh, you should evaluate for pneumothorax at the highest point of the chest for each lung. It’s like reverse dependence. And that, ladies and gentlemen, concludes our tour of eFAST anatomy.
The Evidence: Don’t Just Take My Word for It
- One of the first studies of emergency physicians performing FAST exams
- Prospective study that trained a group of ER docs how to perform a FAST exam on 245 patients
- FAST exams were 90% sensitive, 99% specific, and 99% accurate!
- Basically: These are some impressive numbers! FAST exams are good stuff!
- Prospective study of 312 blunt thoracic and abdominal patients
- Found that ultrasound can detect as little as 20ml fluid in the pleural space (winning!)
- FYI x-ray generally requires at least 200ml fluid to detect fluid in the pleural space
- That means ultrasound is 10 times more sensitive for detecting fluid in the pleural space
- Found ultrasound is 98.1% sensitive for detecting intra-abdominal fluid
Basically – FAST exams are great for detecting free fluid in the abdomen; ultrasound is amazing at detecting fluid in the pleural space and a far superior test than x-ray!
- Prospective study of penetrating cardiac injury comparing 49 patients receiving ultrasound to controls
- Found ultrasound group had significantly faster rate of diagnosis, disposition to care, and survival rates.
- The ultrasound group had 100% survival. The control group had 57% survival.
That’s a huge difference! I mean come on. A cheap, bedside, non-invasive, radiation-free test that raises your chance of survival from 50/50 to 100% is a no brainer. Basically: Pericardial ultrasound = good. No pericardial ultrasound = bad. No ultrasound = patients dead. Pericardial ultrasound gets patients with pericardial injury to definitive treatment faster with better survival outcomes. End of story.
- Prospective study of pericardial ultrasound in 261 patients with penetrating truncal injuries
- Found pericardial ultrasound 100% sensitive, 96.9% specific, and 97.3% accurate.
- Found average time from ultrasound to operating room was 12 minutes (that’s crazy fast!)
- Basically: Pericardial ultrasound identifies pericardial injury quickly and accurately, so patients can get definitive care faster.
Droppin’ Knowledge: Facts, Pearls, and Pitfalls
Advantages of Ultrasound
- Faster than CT or x-ray
- Performed at the bedside simultaneously with other medical care
- A superior test is many cases (hemothorax, pneumothorax, etc.)
Limitations of Ultrasound
- It’s not as reliable for detecting solid organ lesions
- But let’s face it… these probably aren’t as emergent as the raging hemorrhage into the abdomen cases anyways
- Too much fat is bad. It’s bad for the patient and bad for ultrasound. Getting good images on an obese patient is hard! Be aware of this! (Personally, I troll the ER for obese trauma patients and re-eFAST them, so I’ll be better at obese patient ultrasound when there’s an emergency and it really counts.)
- Subcutaneous air can distort ultrasound images. If you feel subcutaneous rice krispies, ultrasound imaging might be difficult.
- Repeat the eFAST if your clinical suspicion remains high. Repeat scanning increases the test’s sensitivity.
- There may be a slow bleed and there wasn’t enough free fluid for a positive exam initially
- Lower limit of fluid detection in the abdomen is 200 ml of fluid
- Trendelenburg position can make the upper quadrant views more sensitive
- Reverse Trendelenburg can make the pelvic view more sensitive
- Don’t be afraid to get low on the pelvic view. If it feels awkward, you’re probably doing it right.
- Try to get your pelvic view before they put in the Foley. A full bladder is a visible bladder.
- If you can can’t get the LUQ view, move superior and posterior. The kidney is higher on the left side. Make sure you’re knuckles touch the bed. If they’re not, you’re not posterior enough.
- Don’t delay care waiting for an eFAST on patients that obviously need surgical intervention (like an abdominal evisceration)
- Don’t get tricked by perirenal fat. Free fluid is darker than fat.
- Don’t get tricked by epicardial fat pads. Same rule as above. Fluid is darker than fat.
- Don’t get crank your probe to extreme angles to visualize the bladder. Keep your probe perpendicular to the patient to avoid false positives and negatives in the pelvis.
- Don’t miss blood because it’s clotted. Clotted blood has varying echogenicity (shades).
A Quick Note for Medical Students New to Trauma
Patients are people and they’re generally scared. You will be close to the patient’s head during an eFAST. Don’t be caught off guard if a scared trauma patient looks to you for information or comfort because you’re so close. This is a little obvious, but as a student sometimes we forget these things. The first time this happened to me a trauma patient (that I thought was obtunded) opened his eyes and grabbed my arm. I jumped so hard it was like he shocked me. He was scared and asking if he was paralyzed. It took me a second to get my wits together enough to tell him that moving his arms and legs was a good sign. Just be aware that if you’re doing an eFAST on a trauma patient, you may be the closest person the patient can talk to. Be nice.
Quiz Yo’ Self
The eFAST is a great ultrasound exam. It’s faster than other imaging and can be done in just a few minutes (a huge plus for the hemodynamically unstable patient). It can be performed at the bedside without interrupting ongoing medical care. There’s no radiation, unlike CT or x-ray. It’s sensitive, specific, and accurate. And it’s a superior diagnostic tool for a number of conditions, like pneumothorax and hemothorax. eFAST ultrasounds save lives! The scan consists of a RUQ, LUQ, pelvic, cardiac, and lung ultrasound. And to top it all off, it’s not hard to learn. I promise! This is a foundational ultrasound exam in emergency medicine and should be a part of any physician’s physical exam skills. Now go practice some eFASTs! And be sure to check out the Quick Hit post for all the info from parts 1 and 2 in summary form!
Here are some extra eFAST resources. I highly recommend the Ultrasound Podcast if you want to learn more about ultrasound!
Submitter: Jennifer Cotton
- Dawson M, and Malin M. Oct 24, 2012. Introduction to Bedside Ultrasound. pp 2-24. Emergency Ultrasound Solutions.
- Dawson M, and Malin M. September 21, 2011. “Episode 08 – A Song for A Scan”. Ultrasound Podcast. http://www.ultrasoundpodcast.com/2011/09/a-song-for-a-scan/, March 2013.
- Lewiss RE, Saul T, and Del Rios M. January 2009. “Focus On: EFAST – Extended Focused Assessment With Sonography for Trauma”. ACEP News. http://www.acep.org/Content.aspx?id=43640, March 2013.
- Ma OJ, Mateer JR, Ogata M, Kefer MP, Wittmann D, Aprahamian C. Prospective analysis of a rapid trauma ultrasound examination performed by emergency physicians. Journal of Trauma, 1995; 38:879-85.
- McNamara D. October 2008. “Use FAST to Quickly Find Fluid in Abdomen, Around Heart”. ACEP News. http://www.acep.org/content.aspx?id=41934, March 2013.
- Plummer D, Brunette D, Asinger R, Ruiz E. Emergency department echocardiography improves outcome in penetratic cardiac injury. Annals of Emergency Medicine. 1992; 21:709–12.
- Reardon R. 2008. “Ultrasound in Trauma – The FAST Exam Focused Assessment with Sonography in Trauma”. Ultrasound Guide to Emergency Physicians. http://www.sonoguide.com/FAST.html, March 2013.
- Rothlin M.A., et al. Ultrasound in blunt abdominal and thoracic trauma. Journal of Trauma. 1993; 34:488-95.
- Rozycki GS, Feliciano DV, Ochsner MG, et al. The role of ultrasound in patients with possible penetrating cardiac wounds: a prospective multicenter study. Journal Trauma. 1999; 46:543-51.
- Stone M. “Emergency Ultrasound Exam”. American College of Emergency Physicians. http://www.emsono.com/acep/exam.html, March 2013