Remember that the eFAST ultrasound exam is most beneficial in hemodynamically unstable patients who are unable to go to the CT scanner. A positive eFAST scan can help the surgeon identify the general region of bleeding (i.e. abdomen vs heart vs lungs) to plan their surgical approach.
A negative initial eFAST exam in patients with a highly-suspicious mechanism of injury may benefit from a CT scan or serial eFAST exams, especially in the context of a worsening clinical status (e.g. worsening vitals, hemodynamic instability, worsening pain, or worsening abdominal exam) as patients can also have a delayed presentation.
eFAST Exam Algorithm
Here is an algorithm for how to use the eFAST exam in the clinical setting:
In the setting of trauma (especially penetrating trauma) you may encounter pneumoperitoneum, or free air within the peritoneal cavity.
On abdominal ultrasound, the most common finding for pneumoperitoneum is the Enhanced Peritoneal Stripe Sign (EPSS). This is when air within the peritoneal space rises and causes an “echoing” of the usually single, hyperechoic peritoneal stripe that separates the abdominal wall from underlying peritoneal fluid and fluid-filled organs (Indiran).
If there is a large amount of pneumoperitoneum, your image of abdominal organs will be obscured by air wherever you place your probe.
Tip: if you can’t get any good abdominal views despite having your probe in the correct position, have a high suspicion for pneumoperitoneum.
Here are three important steps to evaluating for pneumothorax when performing the eFAST scan:
First, if lung sliding is present, you can rule out pneumothorax with 100% accuracy at that ultrasound point (Husain LF).
You can look for lung sliding with B-mode or M-mode:
Second, if lung sliding is ABSENT, you should not automatically assume pneumothorax.
Recall other causes of reduced/absent lung sliding: severe consolidation, chemical pleurodesis, acute infectious or inflammatory states, fibrotic lung diseases, acute respiratory distress syndrome, or mainstem intubation.
For the purposes of the eFAST scan, it is highly likely that your patient has a pneumothorax if you do not see lung sliding on B-mode or M-mode. If you want to confirm you can proceed to look for the “Lung Point Sign” below.
Third, if a lung point is present, you can rule in pneumothorax with 100% accuracy (Chan S).
To confirm the presence of a pneumothorax, you should look for the “Lung Point Sign.“
The lung point is when you can see the transition between normal lung sliding and the absence of lung sliding. This is the transition point between the collapsed lung and normal lung. If you see this you can definitively rule in a pneumothorax. The Lung point sign also helps you quantify how large a pneumothorax is.
If you think you may have found a lung point but are not sure, use M-Mode and place your cursor at the intersection where you think lung sliding starts and stops. If you see a normal seashore sign that turns into an abnormal barcode sign, then you have located the lung point with M-Mode.
After evaluating the RUQ or LUQ, move the probe superiorly one or two rib spaces to evaluate the thorax for fluid accumulation.
A normal lung will have a Mirror Image Artifact and you will be unable to see the spine going above the diaphragm since all of the ultrasound waves will be reflected back by the aerated lung.
Visualizing the patient’s spine above the diaphragm implies that there is free fluid (e.g. blood) in the thorax since ultrasound waves can easily pass through the free fluid in the chest cavity, allowing you to see the spine. This is referred to as a Positive Spine Sign
The eFAST is moderately sensitive (approximately 80%) and highly specific (>90%) for detecting free fluid from hemoperitoneum. The general consensus is that there needs to be at least 200-250ml of blood before the eFAST scan will appear positive.
Another important point to remember for the eFAST scan is that observing free fluid on the eFAST scan does not localize the bleeding to a specific organ. For example, if free fluid is noted in the pelvis, it could be originating from anywhere in the abdomen, and does not localize the injury to the bladder. A CT scan is needed to localize the origin of abdominal bleeding in a trauma patient.
Right Upper Quadrant (RUQ) – Hemoperitoneum
The three common locations for free fluid to accumulate in the RUQ of the eFAST scan are the:
Hepatorenal Space or “Morison’s Pouch”
Caudal Tip of the Liver
Left Upper Quadrant (LUQ) – Hemoperitoneum
We will evaluate the LUQ in the eFAST for free fluid in the following places:
TIP: It is important to note that in the LUQ the most common area to find fluid is in the perisplenic space, NOT between the spleen and the left kidney. This is because there is a splenorenal ligament that attaches the spleen and the left kidney preventing a significant amount of fluid to accumulate there unless the ligament is ruptured.
Male Pelvis – Hemoperitoneum
In the male pelvis, you can find free fluid in the rectovesical pouch/space.
Female Pelvis – Hemoperitoneum
In the female pelvis, you can find free fluid in the Pouch of Douglas (Rectouterine Pouch).
Recall that fluid will appear black, or anechoic. For the purposes of the eFAST exam we are looking for anechoic (black) areas in the abdomen, chest, and heart that signify bleeding in those potential spaces.
For pneumothorax we will be evaluating the presence or absence of lung sliding.