CanPoCUS Core Course – Saint John – May 12, 2023
CanPoCUS IP School – Saint John – May 13, 2023
Resuscitative TEE – the whats, the whys and the hows…. A brief review of the literature, examples of use and a proposed cardiac arrest protocol
Professor, Dalhousie Department of Emergency Medicine
Download Slides – PoCUS Rounds – TEE – Nov 2022
http://pie.med.utoronto.ca/tee/
ACEP NOW – How to Perform Resuscitative Transesophageal Echocardiography in the Emergency Department
Dr. Jill Carter Dalhousie EM Resident
Dr. Renee Kinden, PGY2 EM
Patrick Rogers, Clinical Clerk (CC3)
Memorial University of Medicine Class of 2021
Reviewed by Dr. Kavish Chandra
Small bowel obstructions (SBO) are a common cause of acute abdominal pain in emergency departments across Canada. Diagnostic imaging plays a key role in the diagnosis and management of SBO as the history, clinical examination and laboratory investigations lack the sensitivity and specificity needed. Furthermore, diagnostic imaging may help differentiate SBO from other causes of abdominal pain (hernias, malignancies, intussusception, etc).
Historically, plain film abdominal radiography (AXR) has been an initial investigation in emergency departments when an SBO is suspected. However, the current literature suggests that abdominal radiography is a relatively poor test for the diagnosis or exclusion of SBO when compared to other available modalities like US, CT, or MRI. In fact, multiple studies argue for the reduction of abdominal x-rays, especially when patients come in presenting with general abdominal tenderness. 1 Fortunately, there exists a compelling alternative: point of care ultrasound (PoCUS), and is being increasingly used as a first line investigation for SBO. 2
There are several reasons why physicians may start to choose PoCUS over traditional diagnostic modalities:
The current evidence is highly favorable for the diagnostic efficacy of PoCUS in SBO. Here are the findings of peer-reviewed studies on the subject (published between 2013-2020):
There are two major barriers identified in the literature that may prevent the effective use of PoCUS in the diagnosis of SBO. First, not every emergency physician has been trained on the use of PoCUS. Fortunately, two recent studies show that even minimally trained ED physicians can use it accurately. 8 Secondly, some surgeons have argued that PoCUS does not show the location of the obstruction accurately. This becomes a concern when the care team elects for surgical management of the patient’s SBO. However, recent evidence suggests that PoCUS may lead to quicker time to diagnosis and enteric tube insertion in conservative management. 8
Finally, how can learners use this technology? 5 Here are some specific sonographic findings to look for when evaluating a patient for SBO with US:
Figure 1. Dilatation of small bowel loops. Image courtesy Dr. Kavish Chandra
Figure 2. Altered intestinal peristalsis*. Image courtesy Dr. Kavish Chandra
Figure 3. – abnormal peristalsis “to and fro”9
References
Copyedited by Dr. Mandy Peach
Authored and Edited by Dr. Mandy Peach
Big thanks to Dr. Paul Page for leading the discussions in November.
All cases are imaginary, but highlight learning points that have been identified as potential issues during rounds.
Chest pain is a huge topic – this is not a deep dive, but hopefully a helpful review of some useful information for on shift. This post assumes a basic knowledge of bedside ultrasound.
Case
48 yo male presents to the ED with 4 hours of substernal CP. He describes the pain as sudden onset and waking him from sleep overnight. He feels sweaty and has had 2 episodes of nausea/vomiting. He denies any fever or diarrhea. He had a similar episode last week that spontaneously resolved after 3-4 hours. He has no history of exertional chest pain. His cardiac risk factors include hypertension and his father died of ‘heart problems’ in his late 60’s.
An ECG is completed:
On exam his vital signs are within normal limits. He appears slightly diaphoretic and uncomfortable. Cardiorespiratory exam is unremarkable.
What are the BIG can’t miss diagnoses for chest pain? What bedside tool can be helpful in diagnosing some of these conditions?
Acute Myocardial Infarction (MI)
Pulmonary Embolism (PE)
Tension Pneumothorax
Aortic Dissection
Cardiac Tamponade
Esophageal Rupture
The ECG is unremarkable for ischemic change. You order a cardiac work up, including a CXR. While you await these results, you reach for your nearest ultrasound probe. You perform a cardiac and lung scan:
Figure 1 – normal subxiphoid view of the heart
Figure 2: Normal lung slide with visible A lines
You do not see any large pericardial effusion and on an eyeball observation the heart appears to have grossly normal form and function. The lung scan appears unremarkable with no sign of pneumothorax after viewing multiple rib spaces anteriorly and laterally.
How accurate is ultrasound at helping you rule in/out some of the major chest pain diagnoses?
Cardiac tamponade – Trained emergency physicians using beside ultrasound are quite effective at identifying significant pericardial effusions with a sensitivity of 96% and specificity of 98%1.
Figure 3: Large pericardial effusion with collapsing of RV
Pneumothorax – Lack of lung sliding and comet tails has a specificity of over 90% in ruling in pneumothorax. Time constraints? 1 view has comparable sensitivity to 4 views in picking up a clinically significant pneumothorax2
Figure 4: Absence of lung sliding or comet tails indicating pneumothorax
Pulmonary Embolism – Although no one finding is pathognomonic for PE, signs of RV dysfunction in the right clinical context is certainly suggestive of acute PE. Findings of:
have a 99% specificity for PE3.
Figure 5: Enlarged RV with free wall hypokinesis at the apex (McConnell’s sign)
Figure 6: Bowing of RV into LV in parasternal short view “D sign”
For advanced scanners, in patients with abnormal vitals (tachycardiac and hypotensive):
significantly decreases the post-test probability for PE4
Aortic dissection – very specific findings – if you see a dissection flap you found it! If not, it’s still a high risk diagnosis you wouldn’t want to miss. There is evidence that when getting advanced cardiac views, suprasternal notch views and visualizing the abdominal aorta the sensitivity of POCUS is 86%5, however this did not translate into mortality benefit and is likely of more benefit for advanced scanners.
With normal vitals and ultrasound findings you feel confident there is no pneumothorax or tamponade. The probability of PE seems quite low given the history. Is there an objective way to risk stratify your patient for PE risk?
Apply the PERC rule 6 in the targeted low risk patients like this one where your physician gestalt of likelihood of PE < 15% . In the appropriate population this tool has a sensitivity of 96%;
The probability of him having a PE is < 2%.
You revisit the history and physical exam keeping in mind your remaining diagnoses of aortic dissection and esophageal rupture.
Are there any tools I can use to help decide if my patient is high risk for aortic dissection?
This tool is for low-moderate risk patients where dissection is in the differential. When this rule was applied to a retrospective population only 4% of dissections were missed. When adding a normal CXR the miss rate decreased to 2.7%. Each feature equals 1 point. Essentially the absence of any high risk feature essentially rules out aortic dissection7. If more than 1 high risk feature, proceed to CT-A. If ≤ 1 this tool suggest ordering d-dimer.
Does d-dimer help rule out aortic dissection?
It’s controversial. If your patient is low risk and dissection isn’t high on your differential, a normal d-dimer doesn’t really add any value. If you order anyways and it is positive, it may lead to unnecessary testing. It certainly should not be used in isolation. The above tool combined with d-dimer had a sensitivity of 98.8% in one study, however this has not been externally validated8 – proceed with caution.
Your patient has no high risk features for aortic dissection.
Your patient did have episodes of vomiting – could they have a ruptured esophagus (Boerhaave syndrome)?
Mackler’s triad – vomiting, chest pain and subcutaneous emphysema – is present in 14-25% of cases so certainly not reliable. Patients can present with mediastinitis and abnormal vitals.9 CXR findings include 10:
With a normal CXR and normal vitals this is less likely.
So, you’ve considered the major diagnoses for chest pain and cardiac ischemia is left to consider – your first troponin result just become available – it is within normal range.
Can you use a single troponin to rule out a cardiac event?
You are now 4 hours from the onset of the event. Over his visit you have ordered a second ECG which is also normal. The troponin is normal – you feel more reassured. But your patient does have some risk factors for cardiac disease. You need to decide how at risk your patient is. You use the HEART score 11to help stratify:
Your calculated heart score is 3 which is low risk.
“A single undetectable hs-troponin after 3 hours of symptom onset or a delta 2-hr hs-troponin T <4ng/L plus normal serial ECGs and a HEART score of 0-3 rules out acute MI and lowers 30-day MACE to well below 1%, a threshold below which ancillary testing may cause more harm than benefit12.”
You feel quite confident your patient has no acute life-threatening cause of chest pain. You settle the pain and nausea in the ED and feel his is safe to go home. You suspect gastritis.
3 days later on shift you recognize the same patient – he again is complaining of chest pain, but today he looks much worst. You grab his chart – he is mildly tachycardiac, but otherwise vitals are normal. ECG again looks normal.
Today the patient describes having worsening nausea, fatigue and chest pain. His pain is more persistent and is not relieved with OTC medication at home. When you ask him to point to the pain he points towards his epigastric area – not substernal as he previously complained of.
This visit you complete an abdominal exam and find significant RUQ tenderness.
What are some other causes of chest pain, that although not immediately life threatening, should be considered13?
You grab your ultrasound probe as you suspect cholecystitis, what are the ultrasound findings?
Thickened gb wall > 3.5mm and fluid surrounding the gallbladder as seen above14.
You confirm cholecystitis and consult surgical service. On formal imaging the radiologist is concerned for potential perforation of the gallbladder.
Bottom line – chest pain has a broad differential! Grab your ultrasound probe and use some evidence based tools to help narrow your differential. Once life threatening causes ruled out consider other causes that can still affect patient morbidity.
References and further reading:
All ultrasound gifs from The PoCUS Atlas https://www.thepocusatlas.com/
Dr. Scott Foley – CCFP-EM PGY3 Dalhousie University, Halifax NS
Reviewed by Dr. David Lewis
When colour Doppler is initiated, the machine uses the principals of the Doppler effect to determine the direction of movement of the tissues off which it is reflecting.
The Doppler effect is the change in frequency of a wave in relation to an observer who is moving relative to a wave source. It was named after the Austrian physicist Christian Doppler who first described the phenomenon in 1842. The classic example is the change in pitch of a siren heard from an ambulance as it moves towards and away from an observer.
These principles are applied to POCUS in the form of colour Doppler where direction of flow is reflected by the colour (Red = moving towards the probe, Blue = moving away from the probe), and the velocity of the flow is reflected by the intensity of the colour (brighter colour = higher velocity).
*Note: the colour does not represent venous versus arterial flow.
The use of colour Doppler ultrasound can be useful in the emergency department to determine vascular flow in peripheral vessels as well as through the heart. It is one way to determine cardiac valve competency by focusing on flow through each valve.
To optimize valve assessment, proper views of each valve must be obtained. It is best to have the direction of the ultrasound waves be parallel to the direction of flow. External landmarks for the views used are seen below:
Parasternal long axis: MV, AV
Parasternal short axis: PV, TV
Apical 4 chamber: TV, MV
How to examine valvular competency:
See video tutorial below for more
Mitral Regurgitation A4C
Tricuspid Regurgitation A4C
Aortic Stenosis PSLA
Color flow Doppler on POCUS is a straightforward way to assess for valvular competency in the Emergency Department. A more detailed valvular assessment requires skill, knowledge and experience.
Robert Dunfield – PGY1 FMEM Dalhousie University, Saint John NB
Reviewed by Dr. Kavish Chandra
Mr. JG, a 34 year old male snowboarder, presents to your busy emergency department after a snowboarding accident. He suffered a fall onto his left outstretched hand after hitting a jump that was approximately one foot high. Radiograph shows a closed distal radius fracture with significant dorsal angulation.
Tonight is a busy shift and you’re working in a resource-limited department with very few staff. In speaking with the patient, he’s nervous about the prospect of procedural sedation and would prefer to not be “put to sleep to fix [his] wrist”. Luckily, your department recently purchased an ultrasound machine and the patient consents to a hematoma block prior to reduction.
Following the initial impact that causes a fracture, the initial stage of bone healing involves a hematoma formation. In simple terms, a hematoma is a large blood clot that collects at the fracture site. Hematomas are rich in vascular supply and are the site of eventual soft callus formation; they’re the result of bony blood supply being disrupted at the site of the defect
Stages in Fracture Repair. The healing of a bone fracture follows a series of progressive steps: (a) A fracture hematoma forms. (b) Internal and external calli form. (c) Cartilage of the calli is replaced by trabecular bone. (d) Remodeling occurs.1
Compared to procedural sedation, hematoma blocks can be done safely when procedural sedation is not an option or is contraindicated. They also offer an alternative option for analgesia when an emergency department is busy and resources are lacking to safely perform procedural sedation.2
Prior to the advent of bedside ultrasound, hematoma blocks were dependent on external anatomy landmarking, using “step-off” site of the bony deformity as the landmark for injection. This can be difficult, however, in fractures where swelling, habitus, or deformity can distort the anatomy of the hematoma.2 This is where ultrasound plays a role in identifying the deformity and therefore improves the precision of hematoma injection.
Contraindications to hematoma block include allergy to the anaesthetic being used, if the fracture is open, if there is cellulitis overlying the site of the fracture, and/or if there is a neurovascular deficit on exam of the affected limb.5
Mr. JG requires reduction of his distal radius fracture. Due to his uneasiness with procedural sedation, combined with the busy and resource-strained nature of your emergency department, a hematoma block under ultrasound guidance is performed.
Left: Sagittal image of left radius outlining an interruption in the radial cortex at the site of the hematoma. Right: Same image, edited to identify anatomy.8 Edited by Robert Dunfield PGY1-Dalhousie
Injection of hematoma block under ultrasound guidance.6 Modified by Robert Dunfield PGY1-Dalhousie
Summary:
Copyedited by Kavish Chandra
Resources: