Hemodynamically unstable, sick patient have high mortality and morbidity. Their physical exam findings can be misleading and the diagnosis still broad or unclear even after examination. When time counts and your patient is sick, bedside ultrasound can quickly make the diagnosis to help you provide appropriate and definitive care when it matters most. This is the basis for the SonoSave series, which examines ultrasound saves and the critically ill patients alive today because of point of care ultrasound.
Ultrasound is a lifesaver and luckily for a recent patient I mean this literally. Thanks to the early use of ultrasound a life was saved that would have been lost. A critical diagnosis was made within 5 minutes of arrival, preventing investment of precious time in ineffective treatments or delaying definitive care and making me look real slick in the process. The patient was successfully treated and admitted to the ICU. When I walk into work the next day, I find out the patient is not only alive but sitting up in bed talking to the team! With some simple ultrasound views and less than 2 minutes, the direction of our treatment completely changed and a man lived to see his family that I doubt would have otherwise. Two minutes to save a life… that’s some good stuff and even better ultrasound! These are the moments that make medicine worth it.
That Feeling When You Walk Out of Your Shift After A Good Save
Now let’s get into the case. EMS calls over the radio. “This medic 22. We’ve got a 51 yo male coming in with sepsis. Recently discharged from extended admission to your facility for sepsis from a gluteal wound and skin infection. He was discharged and sent to the SNF for IV antibiotics. Heart rate is 128, BP is 76/45, pulse ox 93%, RR is 22. Patient is awake and talking to us. His only complaint is sweating. See you in five.” Another doc leans over, “Sounds pretty straight forward. It’s just sepsis. Antibiotics and fluids… It’s all yours.”
The patient is sleepy but talking in full sentences with little distress, when he arrives in the resus bay. Nurses get IV access, he is connected to monitors, and I receive medic report. Patient has been getting IV antibiotics via PICC. They don’t know exactly why the SNF called them and neither did anyone at the facility (business as usual). Patient reports feeling tired and sweaty just before the medics arrived, but has no other complaints. Pressure is now 70/48, HR is 120-130s, oxygen sat in 90%, RR 22, temp 98.9. I examine him. He is obese, oriented x 3, tachycardic with 2/6 systolic murmur, lungs are clear, abdomen is soft without tenderness, pulses present in all 4 extremities, has bilateral lower extremity edema, his gluteal ulcer is well healed with minimal surrounding erythema. I ask the patient several questions. Any history of heart failure, MI, blood clots, COPD, CAD, any lung or heart disease whatsoever? None. Any fever, cough, chest pain, nausea/vomiting, shortness of breath, focal weakness/numbness, abdominal pain, diarrhea, bloody or tarry bowel movements, dysuria or frequency, drainage from previous ulcer site, lower extremity pain? Nope. Nope. Nope. Known heart murmur? Unsure. He just feels sweaty and tired. EKG shows sinus tach without ischemic changes. We hang fluids and I grab the ultrasound.
I perform the RUSH (Rapid Ultrasound for Shock and Hypotension) exam that I use for all undifferentiated hypotensive patients. My first two views make the diagnosis clear, PE. The right ventricle is significantly larger than the left ventricle, which is is contracting enthusiastically. The IVC is huge, so are the hepatic veins. It’s not collapsible at all. This is NOT sepsis! This is obstructive shock and without any pulmonary history I doubt another cause of this acute RV dilation. PE is the obvious answer. I move lower and check for DVT to further support my diagnosis. Nothing in the femoral veins, but I strike gold in the left popliteal vein and diagnose a DVT. Ladies and gentlemen, this patient has obstructive shock from a pulmonary embolism.
Apical Four Chamber – Right Ventricle Dilation
Popliteal Fossa – DVT
I tell the room its a PE not sepsis and call the scanner to tell them we’ll be there in 2 minutes to confirm the diagnosis. Sadly, I have to do this because the ultrasound penetrance at this community hospital I am working in today is quite poor. If the other EM docs who pop in to see if I need a hand looked at me funny when I proudly announced my findings, I doubt the intensivist/cardiologist/surgeon I am dealing with will buy a beside ultrasound diagnosis. It is unlikely they will trust the new person with an ultrasound over the diagnosis momentum of sepsis already in place. I walk the patient to the scanner myself and pharmacy starts mixing TPA. The tech mutters “daaaamn” as the images come up… it’s a massive saddle embolism, the largest I’ve ever seen in a live person. Less than 15 minutes from arrival we have a diagnosis and definitive treatment plan. Fluids are stopped, TPA is given, light pressors started, the patient goes to the ICU, and I buy myself a little street cred at a new hospital.
I am thankful for my ultrasound training and start to think of how this would have gone down without it. I shudder. I imagine thinking this was sepsis and how this would have likely driven the treatment plan for several hours. The chest xray might have looked like pneumonia as the lung infarcted, further supporting infection and explaining his borderline oxygen sat. The patient would have failed to improve and I doubt I would have taken him to the CT scanner so early or at all as the treatment of sepsis worsened his hemodynamics. Instead he would have been slammed with fluids for his hypotension, driving his RV further off the starling curve onto complete failure and cardiac arrest. A long and painful code later I would have been drained, but told myself and his family I did everything I could. Instead, thanks to point of care ultrasound, just one day after a massive saddle embolism the patient is sitting up in bed talking. Without point of care ultrasound this patient (someone’s son, husband, father) would have likely died. This is a win for point of care ultrasound and especially for this patient, and definitely qualifies as a SonoSave!
Ultrasound for Massive PE
So let’s talk ultrasound for pulmonary embolism. There are three areas to ultrasound that support the diagnosis of massive PE – cardiac, IVC, and DVT. You certainly don’t need to do all of these to make the diagnosis. In this case I completed cardiac and IVC scans to make the diagnosis of obstructive shock and used DVT scan to further support my PE diagnosis. Some people include lung ultrasound in their PE assessment, but I don’t find it gives me much additional information to support the diagnosis and can take time away from patient care when PE is your primary concern. Lung ultrasound IS great to look for other serious pathology in critically ill folks though, so remember it for other sick patients. But for PE ultrasound it’s three quick scans and 2-3 minutes to change the course of patient care and save a life.
The biggest value for bedside ultrasound in pulmonary embolism is in the unstable patient. These patient have significant right ventricular dysfunction and compromised hemodynamics, which in an otherwise healthy person requires occlusion of approximately 50% of the pulmonary vasculature. These are patients that need rapid diagnosis and treatment to prevent the significant morbidity and mortality associated with RV failure in massive PEs. Yet such patients are often too unstable to go to the CT scanner, so how do you diagnose their PE? With ultrasound of course! These patients are also so far down the starling curve of their right ventricle that the common treatment of hypotension with IV fluids will only drive them further down the curve, leading to death. This is because as the preload increases several things happen. First, an already failing right heart gets further stretched by the increased preload and RV output decreases as the cardiac myocytes get further stretched down the wrong side of their starling curve. The increase in right heart pressure also causes encroachment of the right heart into the left ventricle, leading to decreased left heart preload and decreased cardiac output for the left heart. This combination of decreased right and left heart output worsens blood pressure and the resulting shock with each bolus of IV fluids. For these reasons early diagnosis is key in the massive PE to prevent harmful interventions that are used to treat other causes of hypotension. This is why be bedside ultrasound is the safest and most reasonable tool to diagnosis massive PE in the unstable, hypotensive patient.
Heart & IVC Ultrasound: IVC & heart ultrasound are the most useful scans when looking for massive PEs and help paint a picture of obstructive shock. These also happen to be a part of the RUSH exam, which is an ultrasound exam for patients with undifferentiated hypotension. My fastest time for a quality RUSH scan to date is < 2 minutes, so it’s certainly worth knowing and being good at this scan. But I digress… let’s get back to PE ultrasound.
An apical four chamber view is all you need cardiac wise. This view shows you RV size and LV function in one view. The RV should be on screen left (if you positioned your probe marker correctly). Normally its smaller than the LV and should measure less than 60% of the LV (0.6:1 for RV:LV). This does not need to be directly measured. Just eyeball it and know a > 1:1 ratio is very concerning. Another sign of PE is a thin RV free wall with retained function at the apex. This is known as a McConnell’s sign and looks like a fat man is bouncing on a trampoline at the apex of the RV. This is specific, but not sensitive and does not rule out PE. It is also important to confirm the ventricle you are called a strained RV is in fact the RV (and not the normal appearing LV misplaced on the left screen due to probe marker placement). Luckily there are a few ways to confirm your RV. It is more tapered at the apex, its valve is more apically attached to the septum, it does not have an aortic outflow tract when you fan anteriorly, it may have a visible moderator band, and you can confirm the correct position of your probe marker. You also happen to get a view of the LV with the apical four chamber, so you can also eyeball LV squeeze and ensure cardiogenic shock of the left heart is not contributing to your clinical picture. If you’re feeling fancy, you can also get a parasternal short view of the heart and see the LV become D-shaped as right heart pressures overcome left heart pressures and the RV encroaches on the LV. But really one view gets you what you need to know, so make the apical four chamber your view of choice.
The IVC view will give you insight into right heart pressures and fluid responsiveness. If pressures build up in the right heart, this will translate to the IVC and its appearance on ultrasound will further confirm you concerns for obstructive shock from PE. A large (> 2cm) IVC that does not collapse with respiration is concerning for high right heart pressures and pulmonary obstruction (or cardiogenic shock with fluid overload, which you ruled out with your left heart assessment in your four chamber view). Large dilated hepatic veins emptying into the IVC just caudal to the diaphragm can further support you assessment of the IVC and conclusion that high right heart pressures are high. If the IVC is large without respiratory variation and the right heart is dilated, their blood pressure is unlikely to respond to fluids. Further fluids will likely worsen cardiac output and a change in management to pressors would be more beneficial. IVC and cardiac views can be quickly acquired at the bedside and will paint a picture of obstructive shock in the unstable PE patient.
DVT Ultrasound: Two region compression ultrasound is a great way to assess for DVT with sensitivities in the mid 90s. Almost 95% of lower extremity DVTs will be located in the vessels scanned by this method. You will scan in two regions, the groin and the popliteal fossa. The idea is to assess compressibility of the veins. If there is a clot proximal to your probe, then the vessel won’t completely collapse with compression. Press with enough pressure until you deform the artery. If the vein does not completely collapsed, then there is clot. If you suspect PE and find a DVT, there is likely a PE.
Femoral Vein – No DVT
Popliteal Fossa – DVT
PE Mimics: It’s also important to be aware of PE ultrasound mimics. COPD and pulmonary hypertension will cause dilation of the right ventricle over time. However these will generally developed slowly and as a result have associated RV hypertrophy. The RV free wall should be < 5 mm thick in the acute setting, so be aware of this to help distinguish chronic RV dilation from acute. RV infarcts can also cause some RV dilation on ultrasound, so be sure to check for inferior MI pattern on the EKG to assess for this. Basically RV infarct, COPD, and pulmonary hypertension cause RV dilation and increased right heart pressures that can be seen in the IVC; but now you know how to distinguish these mimics from an acute massive PE.
Quick Nutshell of PE Ultrasound: How about a quick summary after reading all that goodness above? Essentially you are looking for a dilated RV, a large IVC that doesn’t change with respiration, and possibly a DVT. Because of how simple and quick it is to find these with bedside ultrasound, it is incredibly useful in the undifferentiated hemodynamically unstable patient and will help you quickly provide definitive treatment to patients when time matters. That’s it. End of story.
Obtaining the Views
Skip this section if you’re already comfortable with obtaining the views for IVC, apical four chamber, and DVT ultrasound.
Cardiac: The apical four chamber heart view is obtained by placing you probe at the apex of the heart, usually inferior to the left nipple, and fanning anteriorly towards the base of the heart/the right shoulder. You want the apex of the heart towards the top center of your screen, so that when you fan/rotate to get your image you won’t get off axis cuts through the heart and accidently underestimate the right heart size. You’ll also want to rotation your probe very slowly once you get all four chambers in view to make sure you see the whole RV and not an off axis slice that would underestimate its real size. Now what follows is really important to getting your image correct. If your screen marker is in the conventional position on the screen left, then your probe marker should point to the left (aka patient right). If your screen marker is in the cardiology position on screen right, then your probe marker should point to the right (aka patient left). This way your probe marker and the screen marker match and you won’t get an accidentally flipped view of the heart and mistake the right heart for the left heart. That’s all you need to know to get a good view of the right heart for PE ultrasound. If you want to read more, take a look at this Cardiac Basics Cheat Sheet.
Handsome Model Demonstrating Apical 4 Chamber Positioning
IVC: While some think the IVC can be difficult, it can easily be found with a systematic approach. Start with your probe marker facing patient right just inferior to the xiphoid, flatten your probe, and angle towards the right shoulder to obtain a basic subxiphoid view of the heart. Once you see the heart and have it roughly centered on your screen turn the probe 90 degrees (probe marker towards head) and angle the probe a little under the ribs. Because the the IVC empties into the right atrium you can follow it coming right out of the RA and through the liver. You might also see hepatic veins emptying into the IVC at roughly 90 degrees to further confirm you are looking at the IVC. If this view fails, try a “rescue view” by placing the probe in the right upper quadrant at the mid axillary line. You will see the IVC go through the liver just anterior to the kidney. Remember the aorta can sometimes be seen in this view, so don’t be fooled. Check out One Minute Ultrasound’s IVC video for more info.
DVT: DVT ultrasound is one of my favorite scans. Once you know your anatomy, it’s a pretty simple scan. Does the vessel compress or not? Lower extremity DVT scanning involves assessing compressibility in two regions, the femoral and the popliteal areas. Start at the femoral vein, just inferior to the inguinal crease and medial the femoral artery. Assess compressibility there. Follow the common femoral vein slightly inferior and assess compressibility at the greater saphenous vein (as it branches medially) and the deep femoral vein (as it branches posteriorly). You have now completed the femoral region in just a few sweeps of your probe. Now move to the popliteal fossa behind the knee. The popliteal vein will be more superficial, so the “pop”liteal vein will be “on top” of the screen (“pop on top” to remember this). Assess compressibility here at the proximal popliteal vein. Scan inferior to to its trifurcation (anterior tibial, posterior tibial, peroneal veins) and assess compressibility of the proximal calf veins. That’s it. Two regions, vein compression, and knowing your anatomy makes for a quick, easy DVT scan. Check out this DVT Cheat Sheet for a refresher before your next DVT scan.
Prove It – The Evidence for PE Ultrasound
EM Physicians Are Pretty Good at Finding RV Dilation
- Prospective study: 3 EM physicians acquired cardiac ultrasound for patients being evaluated for PE & compared their interpretation to fellowship-trained ultrasound expert
- 96% agreement between the EM docs and ultrasound expert on presence of RV dilation
- Basically EM physicians can acquire & interpret ultrasound images to diagnosis RV dilation
- Read It for Yourself
Sick PE Patients have RV Dilation
- Same prospective study as above with EM physician acquired & interpreted ultrasound images. Correlated ultrasound findings to all patients with CT confirmed PE and for PE patients admitted to ICU.
- 100% of patient admitted to ICU and 100% of saddle embolisms had RV dilation. RV dilation was 98% specificity (100% in patients without COPD) and 50% sensitive for PE.
- Basically, RV dilation is a good rule in test for PE and was present in the sickest PE patients (those requiring ICU admission).
- Read It for Yourself
If There’s a DVT…
- Prospective study of 524 patients suspected to have PE who had CT PE and DVT ultrasound.
- DVT ultrasound was 99% specific and 39% sensitive. Positive likelihood ratio was 42.
- Presence of DVT on ultrasound in patients suspected to have PE is a good rule in test.
- Read It for Yourself
We all got into medicine to do good and save lives. If you want to be the doctor that young, hopeful medical student/resident you would be proud of, this is an essential scan set. You will save lives that others miss and that kind of save is the most satisfying, the saved life that someone else might have missed and is alive because you were there. As we all know PEs are sneaky and haven’t read the text books. Many present without profound hypoxia, chest pain or evidence of DVT on exam; even when they are massive. If you mistreat this hypotensive patient population with our most common treatment for hypotension (IV fluids), you will likely cause harm and may kill your patient. Getting the ultrasound views takes 2-3 minutes at most and gives you valuable information. This valuable information will enable you to diagnose the cause of shock in patients too unstable for other advanced imaging modalities and allow you to initiate life saving treatments in patients where every minute counts. Patients like this are why we do what we do and cases like this absolutely qualify as a SonoSave. So next time your patient is hypotensive and sick, question the diagnosis momentum and pick up the probe. You won’t regret it and your patient will thank you!
If you want to check out more resources, take a look at these great ones. They’re awesome!
- Alder C, Buttner W, Veh R. Relations of the ultrasonic image of the inferior vena cava and central venous pressure. Aktuelle Gerontologie. November 1983. https://www.ncbi.nlm.nih.gov/pubmed/6140870
- Adhikari S, Zeger W, Thom C, Fields JM. Isolated Deep Venous Thrombosis: Implications for 2-Point Compression Ultrasonography of the Lower Extremity. Annals of Emergency Medicine. November 2014. https://www.ncbi.nlm.nih.gov/pubmed/25465473.
- Crisp JG, Lovato LM, Jang TB. Compression ultrasonography of the lower extremity with portable vascular ultrasonography can accurately detect deep venous thrombosis in the emergency department.Annals of Emergency Medicine. September 2010. https://www.ncbi.nlm.nih.gov/pubmed/20864215.
- Cowger Matthews J, McLaughlin V. Acute Right Ventricular Failure in the Setting of Acute Pulmonary Embolism or Chronic Pulmonary Hypertension: A Detailed Review of the Pathophysiology, Diagnosis, and Management. Current Cardiology Review. February 2008. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2774585/.
- Dawson M, Mallin M. Introduction to Bedside Ultrasound Volume 1. Chapter 5 “Rush”.
- Dresden S, et al. Right Ventricular Dilatation on Bedside Echocardiography Performed by Emergency Physicians Aids in the Diagnosis of Pulmonary Embolism. Annals of Emergency Medicine. August 2013. http://edus.ucsf.edu/sites/edus.ucsf.edu/files/wysiwyg/Dresden%20RV%20dilation%20PE.pdf.
- Five Minute Sono. “PE”. http://5minsono.com/pe/.
- Kucher N, et al. Novel management strategy for patients with suspected pulmonary embolism. European Heart Journal. February 2003. https://www.ncbi.nlm.nih.gov/pubmed/12581684.
- Le Gal G, et al. A positive compression ultrasonography of the lower limb veins is highly predictive of pulmonary embolism on computed tomography in suspected patients. Thrombosis and Haemostasis. June 2006. https://www.ncbi.nlm.nih.gov/pubmed/16732375.
- Life in the Fast Lane. “PE”. https://lifeinthefastlane.com/cardiovascular-curveball-011/.
- Lodato JA, Ward RP, Lang RM. Echocardiographic predictors of pulmonary embolism in patients referred for helical CT. Echocardiography 2008, Jul;25(6):584-90.
- Mathis G, Blank W, Reissig A, Lechleitner P, Reuss J, Schuler A, Beckh S. Thoracic ultrasound for diagnosing pulmonary embolism: a prospective multicenter study of 352 patients. Chest. 2005;128:1531–1538.
- Mount Sinai EM Ultrasound. “RUSH”. http://sinaiem.us/tutorials/rush/.
- McIntyre K, Sasahara A. The hemodynamic response to pulmonary embolism in patients without prior cardiopulmonary disease. American Journal of Cardiology. September 1971. http://www.sciencedirect.com/science/article/pii/0002914971901160.
- Nazerian P, Vanni S, Volpicelli G, Gigli C, Zanobetti M, Bartolucci M, Ciavattone A, Lamorte A, Veltri A, Fabbri A, Grifoni S. Accuracy of point-of-care multiorgan ultrasonography for the diagnosis of pulmonary embolism. Chest. 2014;145:950–957. https://www.ncbi.nlm.nih.gov/pubmed/16162754.
- Squizzato A, Galli L, Gerdes V. “Point-of-care ultrasound in the diagnosis of pulmonary embolism”. Critical Ultrasound Journal. May 2015. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4447771/.
- Squizzato A, Rancan E, Dentali F, Bonzini M, Guasti L, Steidl L, Mathis G, Ageno W. Diagnostic accuracy of lung ultrasound for pulmonary embolism: a systematic review and meta-analysis. J Thromb Haemost. 2013;11:1269–1278 https://www.ncbi.nlm.nih.gov/pubmed/23574640.
- Ultrasound Podcast. “PE”. http://www.ultrasoundpodcast.com/2014/05/multi-organ-us-pe-castlefest-2015-registration-open-last-year-ever-foamed/.