Ultrasound Leadership Academy: Assessing LV Function and the RUSH Exam for Shock
Michael Macias
Welcome to the Ultrasound Leadership Academy (ULA) summary blog series. This week, we summarize the assessment of LV function and delve further into the RUSH exam (and briefly touch on ultrasound in cardiac arrest). The ULA is essentially an online advanced ultrasound education experience put on by the team from Ultrasound Podcast which brings cutting edge learning to emergency medicine personnel through a variety of interactive platforms including video lectures, google hangouts with experts, simulation, live conferences and real time scanning with a pocket-sized ultrasound device known as a Vscan.
Over the next year I will be posting summaries of the key learning points from my experience. If you want to learn more about the program you can visit Ultrasound Leadership Academy or Ultrasound Podcast to see more from the hosts of this awesome program.
Intro
Assessing left ventricular function sounds like a daunting task. There are numerous formulas and measurements that ultrasound technicians use to obtain a value for ejection fraction (EF) that we read on the ultrasound report. However for the purposes of point of care ultrasound in the emergency department, we are not concerned with this number. What we are concerned about is: 1) Does the patient have a normal EF, a moderately reduced EF or a severely reduced EF? 2) Does this finding explain the patient's symptoms?
Turns out that emergency physicians are actually really good at estimating EF, so next time you slap a probe on someone's chest to evaluate if their cardiac output is good, bad, or really bad. Do it with confidence.
How to do it?
- Probe: Cardiac
- View: Parasternal Long Axis and/or Apical
- Evaluate the squeeze of the left ventricle. Is it dilated? Is there adequate squeeze? Are ventricular walls opposite from each other contracting symmetrically? The only way to get good at this is to perform this scan over and over and observe what is normal, what is abnormal and what is really abnormal. Once you build a recognition of normal versus abnormal in your head, you should be able to eyeball LV function in a few seconds.
- You can also use the mitral valve excursion to help you. Is the mitral valve opening widely and almost touching the septum on the PSLA view? If yes, then your LV is probably functioning well. This is known as E-point septal separation. Learn more about this technique for assessing LV function here.
- Caveat: Small ventricles appear to have a lower EF than they actually do, don't be fooled by this.
Normal versus Severely Reduced Function
This is a normal PSLA view. Notice nice thickening of anterior and posterior walls which are symmetric during systole. The mitral valve is practically hitting the septum during diastole.
This is a PSLA with a severely reduced EF. Notice the LV is dilated with poor wall thickening during systole. Also observe the mitral valve and its minimal opening during diastole.
The spectrum of LV function will lie in between these two images so start to become familiar with normal versus abnormal (and severely abnormal). Establish a visual continuum of cardiac function ranging from the normal appearance on the left to the badness on the right. Watch the quick tutorial below on assessing LV function from Western Sono.
Tutorial
Assessing the hypotensive patient
Now that you can assess LV function, you should applies this to your medical patient's who present in shock. We are really good and getting an ultrasound probe on your trauma patient's really fast to assess for bleeding, why not do the same when you need answers fast in the dying medical patient?
It is called the RUSH exam and it stands for Rapid Ultrasound for Shock and Hypotension. The components of the exam are the heart, the inferior vena cava, morison's pouch/FAST views, the aorta and evaluation for pneumothorax. Remember HI-MAP as these are the components of the exam:
The RUSH exam
Heart
Probe: Curvilinear (low frequency) or phased-array
Assess the pericardium
View: PSLA or Subxiphoid (Apical can also be used as well)
Is there a pericardial effusion? Do you see tamponade physiology such as RA or RV collapse? Learn how here.
Assess the Right Ventricle
View: Apical, PSLA, PSSA
Are there signs of RV failure such as dilation or poor contractility? If the RV is equal in size or larger than the LV, this is concerning for RV failure. In this case, think PE, RV infarct or isolated RV failure.
McConnell's sign, which is RV hypokinesis with sparing of the apex is very specific for PE.
Assess the Left Ventricle
View: Apical, PSLA, PSSA
Estimate LV function. Is it normal, moderately reduced or severely reduced? If normal, does it appear hyperdyanamic, i.e is the LV vigorously moving to the point the walls are almost touching? Low LV function think cardiogenic shock (infarction, myopathy), hyperdynamic heart think circulatory or volume issue (hypovolemia, acute blood loss, sepsis).
Time to move on to the IVC.
Inferior Vena Cava (IVC)
Probe: Curvilinear (low frequency)
This is the only scan we have not discussed yet. For a quick 5 minute lecture on using the IVC to assess fluid status, watch this excellent video at Emergency Ultrasound Teaching.
Essentially, you are looking to see if the tank is full or empty and correlate this with your cardiac exam. There are different measurements based on whether the patient is breathing spontaneously or mechanically ventilated. Please refer to the original RUSH exam article here for the differences.
Note that ultrasound of the IVC helps move you along diagnostically as well as decide on proper therapeutics whether it is giving fluids or moving straight to pressors.
M (Morison's Pouch/FAST views)
Probe: Curvilinear (low frequency)
Now that we have assessed the heart and IVC, move on to look for occult bleeding. Assess your normal FAST scan quadrants, including the right upper quadrant, left upper quadrant and suprapubic area (Learn here). This can provide important information and suggest diagnosis such as ruptured ectopic or viscus, spontaneous intraabdominal bleeding, or intraperitoneal rupture of AAA.
Think of this as an EFAST and don't forget to peak above the diaphragm to look for hemothorax.
Aorta
Probe: Curvilinear (low frequency)
Ultrasound is not only one of the most sensitive imaging modalities for evaluating for abdominal aortic aneurysm but it is also fast. Make sure to scan the entire aorta in transverse orientation, measuring (or eyeballing) at four levels as shown above (Learn here).
Pneumothorax
Probe: Curvilinear (low frequency) or linear (only if you have time or poor visualization)
Thinking obstructive shock? This may further clinch your diagnosis. Place the probe approximately mid clavicular line bilaterally, starting in approximately the 2nd intercostal space and scan down to the 4th or 5th space; Note on the left to take a diagonal line to avoid the heart. You are looking for:
- Lung sliding: Presences of lung sliding excludes pneumothorax in the area you are viewing
- B-lines: These suggest that there is no air separating the visceral and parietal pleura and therefore no pneumothorax. They do however support pulmonary edema or consolidation.
- Lung point: This is where one portion of the lung appears to be sliding and the other area is not. This is pathognomonic for pneumothorax.
Learn this scan here from our previous post.
And that my friend's is the RUSH exam. Use it in all your medical patient's with undifferentiated hypotension. For the original paper, click here.
Bonus
You now have learned the tools to assessing the patient in shock. Take this one step further and begin to learn about the utility of ultrasound in cardiac arrest. Obviously if someone has a shockable rhythm, then shock them! However if it's PEA, it's not all the same! The EKG and your bedside ultrasound will help guide your resuscitation management and patient disposition if you obtain ROSC. For an excellent discussion on this new paradigm, visit Adelaide Emergency Physicians as they discuss a new PEA algorithm.
THAT'S IT FOR THIS WEEK
If you are interested in learning more about the ULA learning experience, visit their website below:
More on Lung US can be found in "Introduction to Bedside Ultrasound," Volume 1 & 2, from Dr. Mallin and Dr. Dawson. If you are interested in purchasing these ebooks for less than $1, visit Ultrasound Podcast Consumables.
Previous Posts
References:
- Ultrasound Leadership Academy
- Original RUSH Exam Article
- Western Sono YouTube Page
- SonoCloud.org image database