S4E5: The Echo Chamber - eFAST with Dr. Mai Nguyen - Trauma bonus
It’s time to enter the Echo Chamber! Callum kickstarts the first ultrasound bonus of the season, welcoming Dr Mai Nguyen, Consultant in Emergency Medicine at University Hospital Limerick, to join him.
Dr Nguyen is the Director of Ultrasound Training for Emergency Medicine in the hospital, an EGLS instructor and a Level 1 Ultrasound Trainer. In short, the perfect guest to run through all things eFAST in the approach to a trauma patient. If you didn’t want to build your POCUS skills before, you sure will after this episode!
Time to enter the Echo Chamber
Think eFAST!
Don’t wait to use ultrasound as a distinctive diagnostic test - use it as a part of your primary survey to rule in pathologies. While ultrasound has variable sensitivity and is operator dependent, it is highly specific. When it looks like a haemothorax, walks like a haemothorax and quacks like a haemothorax, invariably it’s a haemothorax.
Clinical exam can be tricky in a busy resus and vital signs can be falsely reassuring. Routinely using eFAST in trauma gives you the additional information that means you’re more likely to identify reversible life threatening presentations.
Note for students: A FAST scan (in the context of ultrasound) stands for Focused Assessment with Sonography in Trauma. The aim of FAST scanning is to detect free fluid in the abdomen, pelvis or heart, which in the context of trauma is assumed to be blood, and enable quicker potentially life saving interventions. The “e” in “eFAST” stands for extended, and refers to scanning the thorax to assess for fluid/air (haemo/pneumothorax) in addition to the other areas.
The ABCs of eFAST - Pearls and Pitfalls
8 is the magic number for eFAST (no offense to 3). Sourcing at least 8 windows will give you a good chance of finding any ultrasound-detectable injury or bleeding that there is to find. It’s important to do serial scans where possible as these pathologies can manifest insidiously - remember we’re always ruling in, not out.
RUQ
Dr Nguyen recommends looking in at least 2 windows here. While most trainees are familiar with Morrison’s pouch, there are lots of places for blood to hide, so she advises starting in the supra- and infra-diaphragmatic space and scanning all the way down to the lower pole of the kidney. The caudal tip of the liver is the most sensitive place to look for intraperitoneal bleeds. Remember, gravity will pull the fluid down, so point the probe posteriorly in each of these views.LUQ
Don’t forget to also hunt from above the diaphragm to the lower kidney on the left side as well, but the most sensitive spot on this side for intraperitoneal bleeds is the suprasplenic area.
Learning point: The most sensitive place to look for intraperitoneal bleeding is the caudal tip of the liver on the right and the suprasplenic area on the left.
Pelvis
Dr Nguyen likes to start with a sagittal view here. Be sure to check the Pouch of Douglas (in women) or the vesico-colic space (in men) for blood accumulation. Beware the rule-in system – fluid tends to be undetectable until there is around 200mL present.
Cardiac
Cardiac windows can be challenging to get in the trauma setting, so Dr Nguyen tells us that it is essential to be able to look at at least 2 different views. The xiphisternal angle can be difficult to get in patients who haven’t been fasting, have increased adiposity or have a distended stomach (caused by eg. intubation/extra breaths administered). The parasternal long axis is a good alternative.
Pericardial fat may sometimes be mistaken for pericardial fluid. If there is an effusion or tamponade, the fluid should be concentric around the heart. Look at the posterior aspect of the heart and increase the depth to increase your chances of detecting concerning features.
Lungs
Air will rise in a pneumothorax, so this time remember to look at the most anterior aspect of the chest. Scan for rib shadows and lung sliding, and use M mode to look for seashore sign and barcode sign. This is not totally specific as lung sliding may be absent with intubation, apnoeas or lack of ventilation, so correlation with clinical exam is important.
That being said, ultrasound actually has a better sensitivity and specificity for haemothorax and pneumothorax than chest x-ray. Ultrasound can detect pleural fluid from 20mL and can be completed in about a minute, while chest x-ray requires at least 200mL to be present and can take more time depending on the setup in your department.
Importance of Ultrasound
In our main trauma episode this month (S4E4: Road Traffic Collision - Trauma), you may recall the case of a trauma patient presenting to a district-level ED. CT is not always available in this setting and decisions have to be made about escalation of care, the necessity of transferring to a different hospital and the appropriate team to refer to. Ultrasound is a more accessible test and ideal for adding to the assessment of a trauma to help answer these questions. A quick eFAST scan will help to guide the surgical specialty to recruit, the management and the urgency of the situation.
Even if a CT is obtained, it is only a snapshot in time, and using serial ultrasound scanning can detect evolving injuries not previously detected. Serial vitals, clinical exam and lactates are also helpful to identify concerns in a seemingly stable patient. This is most useful in chest trauma, the area that ultrasound emphasis has migrated to since its original development for abdominal assessment. Serial scanning in the setting of dynamic injuries such as pericardial effusion can catch clinical deterioration, facilitating early intervention and avoiding cardiac tamponade. It is crucial to include repeat POCUS in the management of penetrating chest injuries, especially close to the heart.
Ultrasound is only used as a rule-in tool for a reason. It is not totally sensitive, especially in the case of retroperitoneal bleeding or bowel perforation. Keep this in mind and never rule a pathology out on POCUS alone!
The facts. The numbers.
So what does the research say? Netherton et al conducted a systematic review and meta analysis of the diagnostic accuracy of eFAST in the trauma patient to provide us with some pooled statistics.
For pericardial effusion, the specificity and sensitivity is high (94% and 91% respectively). This high specificity carries across to pneumothoraces (99%). The sensitivity for pneumothoraces was found to be much lower at 69%, thus clinical exam and alternate imaging modalities should be considered where there is a relative index of suspicion and nothing is detected on ultrasound.
That being said, in a trauma setting where you suspect a pneumothorax, if there are consistent findings on ultrasound, that should be enough to act on to either place a drain or escalate to thoracostomy. POCUS can help you to avoid intubation with a pneumothorax or haemodynamic deterioration in the CT scanner! The perfect right-hand-man in your clinical assessment.
All trauma-ed out?
In 2023 alone we’ve covered a case of spinal trauma, a bonus on spinal surgery, two South Africa trauma specials (neurogenic shock and a fellowship experience episode), our most recent episode based on injuries sustained in an RTC and now this Echo Chamber!
This might be the last trauma-based episode of 2023, but we’ve got another episode up our sleeve for your listening delight over the festive season! Keep an eye out on our socials or an ear out on Spotify.
And as ever:
“May your coffee be strong, and your rounds grand.”
Referenced in text.
Helpful resources:
Core Ultrasound have 5 minute videos on how different pathologies appear on ultrasound examination https://coreultrasound.com/5ms-lung/
Meta Analysis, Diagnostic accuracy of eFAST in the trauma patient: a systematic review and meta-analysis https://pubmed.ncbi.nlm.nih.gov/31317856/
