Point of Care Ultrasound Flashcards
What does eFAST stand for?
Extended Focused Assessment with Sonography in Trauma.
What is the original FAST Exam?
Focused Abdominal Sonogram for Trauma consisted of 3 views: the right upper quadrant, the left upper quadrant, and the pelvis to rule out bleeding in the abdomen from trauma.
What does the eFAST exam evaluate?
The extended Focused Assessment with Sonography in Trauma evaluates the lungs and heart in addition to the abdomen.
eFast Ultrasound Indications?
Hemodynamically unstable trauma patient
Abdominal and Thoracic Trauma: Blunt or Penetrating
Previously stable trauma patient with acute worsening in clinical status
eFAST exam Limitations.
Does not localize the injured abdominal organ
Views may be limited in patients with subcutaneous emphysema
Views may be limited in patients who have a hollow-viscus injury with free air in the abdomen
eFast Exam Ultrasound Preparation
Patient Preparation
Patient lying supine with the exam table flat or in the Trendelenburg position (this increases the sensitivity of the exam but is not required).
Describe the concept of Ultasound footprint.
The Ultrasound Probe “Footprint” refers to the area on the probe that comes in contact with the patient’s skin in order to produce an ultrasound image.
It is located at the very tip of the probe and is usually has a soft “rubbery” feel. Depending on the application you may want a smaller or larger footprint. Regarding footprint width from largest to smallest it goes: Curvilinear > Linear > Phased Array
Describe the Linear Ultrasound Probe.
The linear ultrasound probe is a high-frequency transducer (5-15 MHz) that will give you the best resolution out of all of the probes but is only able to see superficial structures. A general rule of thumb is that if you are going to ultrasound anything less than about 8cm, then use the linear probe. Anything above 8cm you won’t be able to see much.
The linear probe will give you a rectangular field of view that corresponds with its linear footprint:
Describe the Curvilinear Ultrasound Probe.
The curvilinear ultrasound probe has a frequency range of 2-5MHz. It is considered a low-frequency probe and has a large/wide footprint, allowing for better lateral resolution (compared to the phased array probe).
The curvilinear ultrasound probe is often used for abdominal and pelvic ultrasound exams. However, it can also be used for cardiac and thoracic ultrasound exams but is limited by the large footprint and difficulty with scanning between rib spaces.
Here is what the Curvilinear probe looks like and how an ultrasound image will appear on the screen. Notice the curved nature of the ultrasound image.
Describe the Phased Array Ultrasound Probe.
The phased array (or sector array) transducer is commonly branded as the “cardiac probe” and has a frequency range from 1-5MHz. It has a similar frequency range as the curvilinear probe but has a smaller and flat footprint.
The advantage of this probe is that piezoelectric crystals are layered and packed in the center of the probe making it easier to get in-between small spaces such as the ribs (notice the extremely small pinpoint footprint on the ultrasound image below).
It is the ideal probe for cardiac scanning however it can perform all of the applications the curvilinear probe can as well (with less lateral resolution).
What are the four basic movements when scanning with an ultrasound probe?
Slide, Rock, Tilt(Fan), Rotate. Another technique that could be considered a “5th” cardinal movement is Compression.
What is the purpose of sliding the Ultrasound Probe?
Sliding involves moving the entire probe in a specific direction to find a better imaging window.
This is usually used to find the best window, move to different areas of the body, or to follow a specific structure (such as a vessel).
What is the purpose of Tilting (Fanning) the Ultrasound Probe?
Tilting the ultrasound probe involves moving the transducer from side to side along the short axis of the probe. It is commonly also called “Fanning” as well.
Tilting will allow visualization of multiple cross-sectional images of a structure of interest. You can apply this technique to structures such as the heart, kidney, bladder, vessels, etc.
What is the definition of Ultrasound?
The definition of “ultrasound” is simply the vibration of sound with a frequency that is above the threshold of what humans can hear. The frequency of ultrasound is by definition, any frequency greater than 20,000 Hz.
However, ultrasound used in medical practice is typically 1,000,000 Hz (1 Megahertz) or greater.
What is the purpose of rotating the Ultrasound Probe?
Rotating the ultrasound probe involves turning the transducer in a clockwise or counterclockwise direction along its central axis. Rotation is most commonly used to switch between the long and short axis of a specific structure such as a vessel, the heart, the kidney, etc.
What is the purpose of rocking the Ultrasound Probe?
Rocking the ultrasound probe involves “rocking” the ultrasound probe either towards or away from the probe indicator along the long-axis.
Rocking allows you to help center the area of interest. This is also referred to as “in-plane” motion because the image is kept in-plane throughout the manipulation.
What is the purpose of compressing the Ultrasound Probe?
Compression with the ultrasound probe involves putting downward pressure on the probe to evaluate the compressibility of a structure or organ of interest.
The most common use is to evaluate for deep vein thrombosis, differentiate between artery versus vein, and evaluation for appendicitis (non-compressible).
What is the Ultrasound Probe Indicator?
The “probe indicator” on the ultrasound probe can be identified as an orientation marker (ridge, indentation, groove, or nub) on one side of the probe. This corresponds to the indicator or orientation marker on the ultrasound image.
Where is the ultrasound image marker found on the screen for standard applications?
Left side of the screen.
Where is the Ultrasound Image marker located in Cardiac mode?
Right Side
Radiographically the body is divided into three distinct planes. What are they?
Sagittal, Coronal, and Transverse
Describe the Sagittal plane.
Parallel to the long axis of the body and separates the body from left to right.
Describe the Transverse Plane.
Perpendicular to the long axis of the body and separates body from top (superior) to bottom (inferior).
Describe the Coronal Plane.
Parallel to the long axis of the body and separates the body from front (anterior) to back (posterior).
Describe the Oblique Plane.
Oblique imaging planes refer any plane that uses a combination of Sagittal, Transverse or Coronal Planes.
Explain Short Axis and Long Axis Orientation
Cylindrical and non-circular structures can additionally be described using the terms Short vs Long axis.
Long Axis: plane parallel to the maximal length of a structure.
Short Axis: plane perpendicular to the long-axis of a structure.
These views can be obtained by rotating 90 degrees relative to each other. These terms are helpful in structures such as vascular and cardiac applications. Also, this is useful when deciding to perform a procedure in a short versus long-axis approach.
What is the recommended Order for the eFAST exam?
Right Upper Quadrant View (RUQ)
Left Upper Quadrant View (LUQ)
Pelvic View
Cardiac View (Parasternal Long Axis or Subxiphoid)
Lungs (Right and Left)
Liver Identification RUQ
Caudal Tip of the Liver
Identification
Right Kidney Identification
eFAST
Hepatorenal Interface
Identification
Diaphragm Identification
RUQ eFAST
Lateral Surface of Vertebral Bodies
Identification
RuQ
eFAST
RUQ normal view of structures
Using the liver as an acoustic window, identify the lung, liver, Morison’s Pouch, diaphragm, and the long-axis of the right kidney.
Morison’s Pouch is where you usually identify free fluid in the RUQ view.
Right Upper Quadrant Probe Position
Orientate the probe indicator towards the patient’s head.
Anchor your probe in the midaxillary line at the 10th intercostal space.
What are the three common areas that free fluid will be found when scanning the Right Upper Quadrant durinig an eFAST exam?
Hepatorenal Space or “Morison’s Pouch”
Caudal Tip of the Liver
Suprahepatic Space
How does Ultrasound create a picture?
It traditionally does this by using an effect called the “Piezoelectric Effect.” This is simply the vibration of a piezoelectric crystal at the tip of the transducer that generates a specific ultrasonic frequency to create ultrasound waves.
These ultrasonic waves can then penetrate through the body’s soft tissue and return to the transducer as reflected ultrasound waves. These returning waves are then converted into an ultrasound image on the screen for you to view.
Explain Wavelength and Frequency as it relates to ultrasound.
Wavelength = length or distance of a single cycle of a wave.
Frequency = the number of sound wave cycles per second.
As wavelength increases, frequency decreases (and vice versa). This is because Frequency is inversely related to wavelength. The SHORTER the wavelength the HIGHER the frequency and the LONGER the wavelength the LOWER the frequency.
Higher frequency ultrasound probes will give you better resolution compared to a lower frequency probe. However they do this at the cost of decreased penetration.
Explain how the frequency of an Ultrasound Probe has an impact on resolution versus penetration it able to achieve.
A high-frequency ultrasound probe will emit shorter wavelengths, so tissues will receive more ultrasound “waves” per unit of time with a high-frequency probe. However, the trade-off with high-frequency probes is decreased penetration because the piezoelectric crystal can only send so many ultrasound waves out before the waves dissipate.
Phased array probe: great penetration, okay resolution
Curvilinear probe: good penetration, good resolution
Linear probe: poor penetration, great resolution
Anechoic
The term “Anechoic” on ultrasound means no internal echoes are emitted and there is a completely black appearance.
This is most commonly seen with fluid-filled structures since ultrasound waves pass through fluid without reflecting any echoes back to the ultrasound machine.
Blood (unclotted), bladder, transudative pleural effusions, ascites, simple cysts, gallbladder.
Hyperechoic
The term “Hyperechoic” on ultrasound means that a specific structure gives off MORE echoes relative to it’s surrounding structures resulting in a brighter/whiter appearance
Hypoechoic
The term “Hypoechoic” on ultrasound means that a specific structure gives off fewer echoes relative to it’s surrounding structures resulting in a darker or more grey appearance.
In the image below this patient has hepatitis with a Hypoechoic (darker) appearing liver compared to the right kidney:
Isoechoic
The term “Isoechoic” on ultrasound means that a specific structure gives off similar echoes relative to another structure on the ultrasound screen.
For example, you may say the Renal Cortex is isoechoic to the Spleen Parenchyma like the image below:
Left Upper Quadrant Probe Position
Grasp the linear probe between your thumb and first finger, like holding a pencil.
Orientate the probe indicator towards the patient’s head.
Anchor your probe in the posterior axillary line around the 8th intercostal space.
You should have your “Knuckles to the bed” since the spleen is fairly posterior.
Left Upper Quadrant View of Structures
Using the spleen as an acoustic window, identify the spleen, perisplenic space, diaphragm, and the long-axis view of the left kidney.
Free fluid in the LUQ is most frequently seen in the perisplenic space (between the spleen and the diaphragm). The reason is that there is a splenorenal ligament limiting the ability of fluid to track in between the spleen and left kidney
eFAST Left upper Quadrant
Probe Position
Place the transducer in the Coronal Plane
Just posterior to the mid-axillary line and aligned with the xiphoid process
You may need to slide the transducer cranally to view the structures of interest.
eFAST LUQ
Spleen Identification
eFAST Caudal Tip of Spleen
Identification
eFAST Left Kidney
Identification
eFAST Splenorenal Interface
Identification
eFAST LUQ
Diaphragm Identification
eFAST LUQ
Lateral Surface of Vertebral bodies
Identification
eFAST RUQ Scan
eFAST RUQ Scan
Free fluid in Morrisons pouch
Hemoperitoneum
eFAST RUQ Scan
eFAST RUQ Scan
Fluid in the right pericolic gutter.
eFAST RUQ Scan
Small amount of free fluid in the hepatorenal space.
Positive
eFAST
RUQ Scan
Free Fluid at the caudal tip of the liver
eFAST
RUQ Scan
Free fluid in Morrisons Pouch and the Suprahepatic Space
eFAST LUQ Scan
Will evaluate free fluid in which spaces?
- Perisplenic space
- Spleen Tip
- Splenorenal Recess
eFAST LUQ Scan
Free fluid in Perisplenic Space
eFAST LUQ Scan
How can you identify a hemothorax?
Presence of an Anechoic collection above the diaphragm
eFast LUQ
Anechoic Strip around the caudal tip of the spleen
Anechoic Strip between the spleen and the diaphragm
