Overview of Focused Assessment With Sonography for Trauma
Traumatic injury, meaning serious harm to the body caused by physical violence or accident, is the leading cause of death for people younger than 45 years old. 80% of these injuries are blunt, not penetrating, with most deaths resulting from hypovolemic shock, which is significant loss of blood or fluids. In fact, internal bleeding in the abdominal cavity happens in 12% of these injuries. Therefore, it’s incredibly important to detect trauma quickly. The best test should be fast, precise, and not involve any harm or discomfort for the patient.
Doctors used to perform a diagnostic peritoneal lavage (DPL) – a method used to detect internal abdominal injuries or blood in the stomach. While this procedure was highly accurate, it is an invasive procedure with a 1% chance of complications. CT Scans, which takes images of the body, are still the go-to method for diagnosing internal abdominal injuries as they can detect as little as 100 cc of fluid inside the abdominal cavity. However, this method can be time-consuming and can be difficult to perform in an emergency department.
The arrival of point-of-care ultrasound, a machine that can create images of the inside of the body using sound waves, has significantly improved how we evaluate and treat patients. The benefits of ultrasound include its easy access in the hospital, being user-friendly, and it can be easily repeated. Moreover, it doesn’t require any radiation or contrast agents, which are substances used to make specific parts of the body show up clearly in diagnostic imaging, and is cost-effective.
Ultrasound was first used to detect fluid inside the abdominal cavity in Europe in the 1970s, but it didn’t become commonly used in the United States until the 1990s. The FAST (Focused Assessment with Sonography in Trauma) protocol has been developed to assess for internal bleeding and fluid around the heart. Many studies have shown success rates ranging from 85% to 96% and precision exceeding 98%. In cases of trauma patients with dangerously low blood pressure, the success rate of the FAST exam is nearly 100%. Trained providers can perform the FAST exam in less than 5 minutes, reducing the time to surgery, the length of the patient’s stay in the hospital, and the need for CT Scans and DPL. Currently, more than 96% of level 1 trauma centers, the hospitals most capable of providing total care for injured patients, include the FAST protocol in their trauma care plans as does the ATLS, a training program for managing the first hours of trauma.
Lately, many hospitals have begun to incorporate the Extended FAST (eFAST) protocol. The eFAST adds an examination of each side of the chest for the presence of blood or air accumulation in the chest cavity.
Anatomy and Physiology of Focused Assessment With Sonography for Trauma
The FAST (Focused Assessment with Sonography for Trauma) medical test checks for abnormal fluid in certain parts of the body. This happens by using an ultrasound to view areas like the pericardium, which is the fluid-filled sac that surrounds the heart, and three spaces in the part of the body that holds your abdominal organs, known as the peritoneal cavity.
The right upper quadrant (RUQ) ultrasound looks at the space between the kidney and the liver (known as Morrison’s pouch), the area next to the colon on the right side, the area between the liver and diaphragm, and the end of the liver’s left lobe. The person carrying out the exam positions an ultrasound probe along the patient’s side, between the 8th and 11th ribs. By starting with the hand flat against the bed, it helps show the kidney, which is behind the other organs. The RUQ view is usually the best at detecting free fluid, catching it about 66% of the time. The most sensitive spot for detecting fluid, however, is along the edge of the liver’s left lobe, with a detection rate of over 93%.
After the RUQ view, a subxiphoid (or subcostal) view looks at the pericardial space – the area around the heart. This is important because ultrasounds can spot even as little as 20cc of fluid in this area. In cases of trauma, the heart can be put under pressure by as little as 50cc to 100cc of fluid. This is different from more chronic conditions where the fluid builds up slowly. The subcostal view helps to differentiate between pleural (lung) and pericardial (heart) water build-up.
Following this, the left upper quadrant (LUQ) is checked for fluid in the spaces between the spleen and the kidney, beneath the diaphragm, and next to the colon on the left side. Depending on the type of test (the extended FAST or eFAST), the exam may also check for fluid in the left lower chest. They do similar check on the right side of the chest while scanning the RUQ. For each chest view, the probe is quickly moved above the diaphragm. If the vertebrae (backbone) are extra visible (also known as the “spine sign”), it can help identify whether there’s fluid in the chest cavity. Notably, an ultrasound is very effective at detecting blood in the chest cavity with up to 100% accuracy.
Lastly, the exam checks for free fluid above the pubic area or in the pouch between the rectum and the bladder in men and between the uterus and the rectum or bladder in women.
The extended version of the FAST exam, eFAST, also checks the front of the right and left sides of the chest to detect if there’s a collapsed lung. Your lung and chest wall typically have a small amount of fluid that helps them move smoothly during breathing. If a collapsed lung is present, the normal sliding of the lung against the inside of the chest wall is disrupted – a sign which is often visible on the ultrasound.
Why do People Need Focused Assessment With Sonography for Trauma
You might need an eFAST exam, which is a type of ultrasound scan, in the following situations:
- If you’ve experienced a blunt or sharp force accident that’s affected your tummy and/or chest.
- If your physician isn’t sure why you’re having symptoms of shock or a sudden drop in blood pressure. An eFAST exam is often included in a kind of urgent ultrasound scan called a RUSH exam (which stands for Rapid Ultrasound for Shock and Hypotension).
When a Person Should Avoid Focused Assessment With Sonography for Trauma
There isn’t any situation where it’s absolutely wrong to use eFAST, a type of ultrasound scan. However, if a patient is in a very serious, life-threatening condition, it’s important that the use of eFAST doesn’t slow down any procedures to stablize their condition.
Equipment used for Focused Assessment With Sonography for Trauma
The eFast exam uses a special tool called a 2 MHz to 5 MHz curvilinear, also known as an abdominal probe. This tool is used in order to speed up the process as it eliminates the need to switch between different tools. However, there’s another tool known as the phased array or cardiac probe which can also be effective, especially with a method called parasternal windows. In the same way, a 5 MHz to 12 MHz linear probe, often referred to as a vascular probe, is the best tool for checking for a condition called pleural sliding.
How is Focused Assessment With Sonography for Trauma performed
An eFAST exam is a medical test using real-time ultrasound images. In this test, you will be lying flat on your back while the doctor scans your abdomen – the area where your internal organs are. They will be using a scanning device called ‘probe’ to improve the images seen on the screen.
There are different parts of your body that will be scanned during the exam:
RUQ: This stands for the upper right part of your abdomen where your liver and right kidney are located. This helps the doctor see the space in-between these two organs, also known as Morrison’s pouch. The doctor will scan the sides of this space and also scan lower towards the liver and higher towards the diaphragm (muscle helping you breathe). Sometimes, the rib shadows can interfere with the image, so the doctor might tilt the scanning device or ask you to hold your breath so they can see more clearly.
Pericardium: This is the protective layer around your heart. The doctor will place the scanning device just below your breastbone and deepen the scan to view the whole pericardium. They will use your liver to help improve the image. Sometimes, due to your body’s shape and size, the doctor may ask you to take a deep breath or try different scan angles to get a clearer image.
LUQ: This indicates the left upper part of your abdomen, where your spleen is located. The areas around your spleen will be scanned entirely. The scanning device will be moved upwards to view the space under your diaphragm and downwards to see the side of your abdomen.
Suprapubic: This area is located just above your pubic bone. A full bladder is best for this part of the scan, but if your bladder is empty, the doctor will tilt the device. They will scan behind your bladder too as fluid can get collected there.
Anterior Thoracic: This is the part of your chest near the lungs. While you are lying down, the doctor will use the scanning device to look for free air that could indicate a collapsed lung. The doctor will check for normal lung movements that look like ants marching on the screen. If the doctor doesn’t see these movements, a different colour or texture on the scan image, or specific signs like the ‘barcode’ sign, these could indicate a collapsed lung.
Various studies have shown that this eFAST ultrasound is more effective than regular x-ray and physical exams in diagnosing collapsed lungs with accuracy levels reaching up to 99%.
Possible Complications of Focused Assessment With Sonography for Trauma
There are no reported problems directly caused by the eFAST exam (a type of ultrasound often used in emergency medicine). However, the ultrasound does have a few weaknesses. For one, it can only identify internal fluids if there are more than 150-200 cubic centimeters present, meaning it’s only 85% reliable. Regularly repeating the eFAST exam can help avoid missing anything.
Sometimes, the test might show a false negative result. This could happen if a patient comes in late and their bleeding has already clotted, leading to a different appearance on the ultrasound. Similarly, other conditions like filled-up abdominal cavities, fluid from dialysis treatment, ruptured ovarian cysts, or failed pregnancies outside the womb can also be mistaken for something else on the ultrasound.
Sometimes, the ultrasound might also not properly tell apart blood and urine in severe pelvic injuries. Also, it isn’t able to assess bleeding happening behind your abdominal cavity.
It’s important to note that the ultrasound’s results depend a lot on the experience and skill of the health care provider doing it, the patient’s body size, and if there are things like excess gas or air-filled spaces in the way. If these factors could be affecting the ultrasound results, other tests or imaging may be necessary, depending on the patient’s condition.
What Else Should I Know About Focused Assessment With Sonography for Trauma?
Ultrasound technology has greatly improved the treatment of traumatic injuries. Various studies, mostly observational, have shown that the eFAST protocol, a type of ultrasound examination, plays a crucial role in evaluating and treating trauma patients. This protocol is recommended by various professional organizations as the standard approach in trauma resuscitation protocols.
The eFAST examination has been proven to reduce the time taken to start an operation, the duration of patient’s hospital stay, and the overall cost of treatment. Additionally, it also lowers the rates of complications and the need for other procedures like CT scans and DPLs (diagnostic peritoneal lavage – a surgical procedure to determine if there is free-floating fluid, most often blood, in the abdominal cavity).
However, it’s important to bear in mind that like all imaging methods, ultrasounds come with certain limitations that we need to understand and consider.
