CanPoCUS Core Course – Saint John – May 12, 2023
CanPoCUS IP School – Saint John – May 13, 2023
A 58-year-old male presents to Emergency Department with sudden onset of chest pain that is radiating to the back. He was also having shortness of breath at the same time of chest pain. The patient later reveals that his past medical history only consists of “bicuspid valve”, and he takes no medication. On examination, he was uncomfortable, but no signs of acute distress. His respiratory and cardiac exam were unremarkable for reduced air sound, adventitious sound, heart murmur, or extra heart sound. ECG was normal and initial cardiac markers were within normal range. His chest x-ray is normal.
You are aware that with his medical presentation and a history of bicuspid aortic valve, you need to consider associated concerning diagnosis (aortic root aneurysm and aortic dissection) within the differential (myocardial infarct, congestive heart failure, pneumonia, etc.).
Bicuspid aortic valve is one of the most common types of congenital heart disease that affects approximately one percent of population. There is a strong heritable component to the disease. Bicuspid aortic valve occurs when two leaflets fused (commonly right and left coronary leaflets) and form a raphe, a fibrous ridge1. The fusion of the leaflets can be partial, or complete, with the presence or absence of a raphe1. Bicuspid aortic valve disease is associated with increasing risks for valve calcification, which lead to aortic stenosis or regurgitation secondary to premature degeneration1. This congenital heart defect is also a well-known risks factor for aortic dissection and aortic dilatation. Reports have estimated prevalence of aortic dilation in patients with bicuspid aortic valve ranging between 20 to 80 percent, and that the risks of aortic dilation increase with age2. Increases risk of aortic dilatation in bicuspid valve disease also leads to a significantly greater risk for aortic dissection2.3.
The majority of patients with bicuspid aortic valve are asymptomatic with relatively normal valve function and therefore can remain undiagnosed for many years. However, most patients with bicuspid aortic valve will develop complications and eventually require valve surgery within their lifetime. Early diagnosis, while asymptomatic, can enable close follow-up for complications and early intervention with better outcomes. However, asymptomatic individuals are rarely referred for echocardiography.
With increasing use of cardiac PoCUS by Emergency Physicians, there are two scenarios where increased awareness of the appearance of bicuspid aortic valve and its complications may be of benefit.
This clinical pearl provides a review of the clinical approach to bicuspid aortic valve and its associated complications and provides guide to enhancing clinical assessment with PoCUS.
Although bicuspid aortic valve commonly presents as asymptomatic, a detailed focused cardiac history can assess for clinical signs and symptoms related to valve dysfunction and its associated disease, such as reduced exercise capacity, angina, syncope, or exertional dizziness1. Information about family history with relation to cardiac disease is essential for a clinician’s suspicion of heritable cardiovascular disease. Red flag symptoms that shouldn’t be missed such as chest pain, back pain, hypertensive crisis, etc. should be specifically identified. They are indicators for possible emergent pathologies that should not be missed (for example: acute MI, aortic dissection, ruptured aortic aneurysm, etc.)
Physical examination findings in patients with bicuspid aortic valve include, but not limited to, ejection sound or click at cardiac apex/base, murmurs that have features of crescendo-decrescendo or holosystolic. Clinical signs of congestive heart failure such as dyspnea, abnormal JVP elevation, and peripheral edema may also be present.
With cardiac PoCUS, it is important to obtain images from different planes and windows to increase the complexity of the exam and to be able to be confidently interpreting the exam. There are four standard cardiac view that can be obtained: parasternal short axis (PSSA), parasternal long axis (PSLA), subxiphoid (sub-X), and apical 4-chamber view (A4C). Each cardiac view has specific benefits.
With the PSLA, the phased-array transducer is placed to the left sternum at 3rd or 4th intercostal with transducer orientation pointing toward patient’s right shoulder. Key structures that should be seen are Aortic Valve (AV), Mitral Valve (MV), Left Ventricle (LV), pericardium, Right Ventricle (RV), Left Ventricular Outflow Tract (LVOT), and portion of ascending and descending aorta8. It is primarily used to assess left ventricular size and function, aortic and mitral valves, left atrial size8. Furthermore, pericardial effusions and left ventricular systolic function can be assessed.
Using the same transducer position as the PSLA the transducer can be centered to the mitral valve and rotated 90 degrees clockwise to a point where the transducer marker points to patient’s left shoulder to obtain the PSSA. With this orientation, one can assess for global LV function and LV wall motion8. Furthermore, with five different imaging planes that can be utilized with this view, aortic valve can be visualized in specific clinical contexts.
The apical 4-chamber view is generated by placing the transducer at the apex, which is landmarked just inferolateral to left nipple in men and underneath inferolateral of left breast in women. This view helps the clinician to assess RV systolic function and size relative to the LV8.
The subxiphoid view can be visualized by placing a transducer (phased-array or curvilinear) immediately below the xiphoid process with the transducer marker points to patient’s right. The movements of rocking, tilting, and rotation are required to generate an optimal 4-chamber subcostal view. A “7” sign, which consists of visualizing the border between liver and pericardium, the septum, and the RV and LV that looks like number 7. This view allows user to assess RV functions, pericardial effusion, and valve functions8. In emergency setting, it can be used for rapid assessments in cardiac arrest, cardiac tamponade, and global LV dysfunction8.
From – the PoCUS Atlas
In assessing the aortic valve, the PSSA and PSLA can be best used to obtain different information, depending on clinical indications. Both views can be used to assess blood flows to assess stenosis or regurgitation. However, the PSLA view includes the aorta where clinician can look for aortic valve prolapse or doming as signs of stenosis and its complications, like aortic dilatation. On the other hand, PSSA are beneficial when assessing the aortic valve anatomy.
From – the PoCUS Atlas
With PSSA view, the normal aortic valve will have three uniformly leaflets that open and form a circular orifice during most of systole. During diastole, it will form a three point stars with slight thickening at central closing point. The normal aortic valve is commonly referred to as the Mercedes Benz sign.
However, the Mercedes Benz Sign sign can be misleading bicuspid valve disease when three commissure lines are misinterpreted due to the presence of a raphe. A raphe is a fibrous band formed when two leaflets are fused together. It is therefore important to visualize the aortic valve when closed and during opening, to ensure all 3 cusps are mobile. Visualization of The Mercedes Benz sign is not enough on its own to exclude Bicuspid Aortic Valve.
Apparent Mercedes sign when AV closed due to presence of raphe. Fish mouth appearance of the same valve when open confirming bicuspid aortic valve
Identification requires optimal valve visualization during opening (systole). Appearance will depend on the degree of cusp fusion. In general a ‘fish mouth’ appearance is typical for bicuspid aortic valve.
In the parasternal long axis view the aortic valve can form a dome shape during systole, and prolapse during diastole, rather than opening parallel to the aorta. This is called systolic doming. Another sign that can be seen in PSLA view is valve prolapse, when either right or non-coronary aortic valve cusps showed backward bowing towards the left ventricle beyond the attachment of the aortic valve leaflets to the annulus. This can be estimated by drawing a line joining the points of the attachment.
In patients presenting with chest/back pain, shock or severe dyspnea who have either known or newly diagnosed bicuspid valve disease, PoCUS assessment for potential complications can be helpful in guiding subsequent management.
Complications of bicuspid aortic valve include aortic dilatation at root or ascending (above 3.8cm) and aortic dissection 5-9.
Valve vegetations or signs of infective endocarditis are among the complications of severe bicuspid valve5-9
Management of bicuspid aortic valve disease is dependent on the severity of the disease and associated findings.
For a patient with suspicious diagnosis of bicuspid valve disease, a further evaluation of echocardiography should be arranged, and patient should be monitored for progressive aortic valve dysfunction as well as risk of aortic aneurysm and dissection. Surgical intervention is indicated with evidence of severe aortic stenosis, regurgitation, aneurysm that is > 5.5cm, or dissection1.
Bicuspid aortic valve disease is usually diagnosed with transthoracic echocardiography, when physical examination has revealed cardiac murmurs that prompt for further investigation. However, patients with bicuspid valve disease frequently remain asymptomatic for a prolonged periods. Michelena et al. (2014) suggested that auscultatory abnormalities account for 60 to 70% diagnostic echocardiograms for BAV in community10.
While there are no published studies on the utility of PoCUS for the diagnosis of bicuspid aortic valve, there are studies on the use of PoCUS as part of the general cardiac exam. Kimura (2017) published a review that reported early detection of cardiac pathology when PoCUS was used as part of the physical exam 9. Abe et al. (2013) found that PoCUS operated by expert sonographer to screen for aortic stenosis has a sensitivity of 84% and a specificity of 90% in 130 patients 11. In another study by Kobal et al. (2004), they found that PoCUS has a specificity of 93% and sensitivity of 82% in diagnosing mild regurgitation12.
There are also limitations of using PoCUS to assess for bicuspid aortic valve disease, or valve disease in general. Obtaining images from ultrasound and interpretation are highly dependent on user’s experiences to assess for the valve9. Furthermore, research is needed to investigate the use of PoCUS in lesser valvular pathology.
When a new diagnosis of bicuspid aortic valve is suspected, a formal echocardiogram should be arranged, and follow-up is recommended.
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. Rawan Alrashed (@rawalrashed)
PEM Physician
PoCUS Fellow
Reviewed and edited by: Dr. David Lewis
A 55 year old man known to have hypertension, diabetes, atrial fibrillation, chronic kidney disease presenting with 1 week H/O fever, SOB, chest pain, cough, fatigability, looking distressed on exam with HR 110, SpO2 of 86% on RA and BP of 87/45. No audible crackles or gallop rhythm, bilateral pitting edema noticed.
So, you are asking yourself should your next step be Fluids or Diuresis ??
Patient presenting to the emergency department as critically ill with shock status presents a challenge in the initial hour to balance their fluid requirements with their volume status to reach an improvement in hemodynamics without causing harm.
Volume status assessment and fluid responsiveness have been investigated using multiple measures ranging from physical examination to laboratory work up to invasive measures. Despite all that, no single or multiple factor have been sensitive or specific enough to guide further fluid management. Currently, PoCUS is progressing widely in aiding the emergency physician to take a decision in assessing patient’s fluid vs vasopressor vs diuretic needs and guide further resuscitation. PoCUS is noninvasive, readily available, reproducible test that can be augmented with other measures to guide fluid management (1).
To simplify fluid responsiveness, patients are assessed on accordance of the Frank-Starling curve. Patients will respond to fluid administration if they are on the ascending portion of the Starling curve and no benefit will be added if they are at a plateau where more harm can occur which is difficult to be predict form physical examination solely (2).
Traditionally volume responsiveness has been assessed by small fluid bolus challenge. A safer alternative to this is passive leg raise (PLR) which is an autotransfusion where you mobilize about 300-500 ml of intravascular volume from the lower limb to the heart by raising the patient legs from 0o to 45o. A Pre-Post assessment of stroke volume within 30-90 sec from PLR can be done to measure the difference where change of 10% consider to be responsive.
This have been shown to have a sensitivity of 77% to 100%, and a specificity of 88% and 99% (1).
PoCUS have been used in volume status assessment and fluid responsiveness using multiple surrogates which can be classified as follows for simplification:
The target of Cardiac PoCUS is to assess for possible causes of hypotension and shock status using the RUSH or SHoC protocol (3).
Two measures can be used to assess fluid responsiveness: the left ventricular outlet tract (LVOT) and the carotid artery where you assess the velocity time integral (VTI) representing the column of blood passing through the vessel through time. This can be used as surrogate of fluid responsiveness before and after the PLR where a change of 10-15% consider as fluid responsive (4).
Cardiac output variation of greater than 14% has a high positive predictive value for the patient being fluid responsive while values less than 10% are associated with a high negative predictive value (1)
Cardiac output (mL/min) = Stroke Volume (mL/cycle) x Heart Rate (bpm)
Stroke Volume= LVOT area x LVOT VTI
PoCUS Technique (4)
Two measurement are applied to the carotid artery: the carotid blood flow and the corrected carotid flow time index. These measure are recently established in the field of cardiac output assessment and accuracy is still under debate with further studies needed.
PoCUS Technique (4,5)
a. The linear transducer is placed at approximately at the level of the thyroid cartilage, with the orientation marker pointed toward the patient’s head (A).
b. The Carotid artery identified in long-axis and the bulb before the bifurcation visualized and the doppler is applied within 2–3 cm proximal to the carotid bulb, interrogation line (green) has also been angled to make it more parallel to the long-axis of the artery.
c. The Doppler angle correction cursor is placed parallel to the direction of blood flow with insonation angles <60° .
d. Carotid artery Doppler waveform with measurement of the systolic flow time (SFT) and total cycle time (CCT).
e. Calculate the corrected flow time index using the following formula (Figure-5):
CFTI=SFT/√CCT
f. Calculate the carotid blood flow using velocity time integral tracing and carotid diameter (Intima to intima) then apply it in this formula (Figure-6):
blood flow=π×(carotid diameter)2/4×VTI×heart rate
Measurements of IVC diameter and respiratory variation with the collapsibility index as a predictor of fluid responsiveness was found to be having pooled sensitivity and specificity of 63% and 73% respectively (7).
PoCUS Technique (8)
Measurements:
Collapsibility Index (Caval Index)
The collapsibility index=(maximal vessel diameter – minimal vessel diameter)÷maximal vessel diameter
It has been demonstrated that venous collapsibility may be inversely proportional to CVP: a 1 mmHg change in central venous pressure correlates to about 3.3% change in IVC collapsibility (9).
IVC diameter (cm) | CI (%) | CVP (mmHg) | |
<1.5 | 100% | <0-5 | Volume depleted |
1.5-2.5 | >50% | <10 | Less predictive of responsiveness |
1.5-2.5 | <50 | >10 | |
>2.5 | 0% | >20 | Volume overload |
Important to note that sole interpretation of the IVC for volume assessment was found to be poorly correlating and thus should be used in conjunction with other measures and integrated on patient presentation (9).
Internal jugular vein is used for the assessment of the central venous pressure in comparable way to IVC. A small study of non-ventilated patients who were simultaneously undergoing CVP monitoring, a mean IJV diameter of 7 mm correlated with a CVP of 10 mmHg (8).
Collapsibility index of the IJV with change of 39% consider the patient as volume depleted but this carries a limitation of the intrabdominal/ intrathoracic pressure effects (4).
PoCUS Technique
This includes assessment of the Hepatic/Portal/Intrarenal veins wave forms which has been correlated to the level of venous congestion thus estimating the end organ volume effects.
Hepatic Vein Doppler mainly reflects the right atrium filling pattern, portal and intrarenal venous Doppler provide additional information about right atrial filling pressure and its correlation with congestive organ injury (10).
PoCUS Technique (9)
Findings: The waveform of the hepatic vein is reversed with higher velocities seen in diastole in states of volume overload. In severe volume overload, retrograde flow is seen in systole (Figure 9)
Findings: Flow through the portal vein is normally monophasic, but in the presence of hypervolemia, pulsatility will be present. This can be quantified using the pulsatility index where a pulsatility index greater than 50% indicates severe volume overload.
Findings: A normal Doppler waveform is continuous. With increasing venous congestion, there is a decrease in the systolic component of the wave with progression to biphasic (systolic/diastolic phases), and with severe renal congestion, there is complete absence of systolic flow showing only diastolic phase.
Figure -13: VExUS grading system for venous congestion using IVC and different venous doppler wave form for categorization.
A meta-analysis showed that LUS is 88% sensitive and 90% specific for acutely decompensated heart failure and was more sensitive at detecting pulmonary edema than CXR (8).
Another meta-analysis determined the sensitivity and specificity of ultrasound for detection of pleural effusions as 93% and 96% respectively. The sensitivity approaches 100% with pleural effusions >100 mL in volume (8).
PoCUS Technique
Findings:
Patient was found to have reduced LV function with Dilated IVC and CI of 15%, VExUS grade 2. Assessment of COP after PLR didn’t show a proper change thus patient was started on diuretic and respiratory support with consideration of inotropic support.
The table below (8) shows a summary of the evidence related to the different used marker for volume assessment from physical exam to the use of PoCUS. Thus, it is imperative that we do not rely on one single tool, but rather integrate both pertinent physical examination and POCUS findings for better probability of coming to the right decision.
Dr. Victoria Landry, R3
Integrated Family Medicine Emergency Medicine Program
Saint John, NB
Edited by Dr. Rawan AlRashed, PoCUS fellow
Copyedited by Dr. Mandy Peach
PoCUS use by the emergency physician for the diagnosis of uncomplicated intrauterine pregnancy have been proven to be affective in expiditing patient management and decreasing the length of stay in the emergency department. In a metanlaysis done by Stein et.al. emergency physiscain performed PoCUS was found to be 99.3% sensitive in ruling out ectopic pregnancy by detecting an Intauterine pregnancy (IUP). In this review, ultrasound findings in the first trimester will be highlighted.
Indication: Confirmed or suspected pregnancy with abdominal pain, vaginal bleeding, syncope, or hypotension(2)
Start with trans-abdominal ultrasound (TAUS) (1,2)
Then Consider the use of transvaginal ultrasound (TVUS) if available, and qualified to use (1)
General principles (1)
Figure 1 – Longitudinal/sagittal view (TAUS): (1)
Figure 2 – Transverse view (TAUS): (1)
Discrimination zone (βHCG levels below which you cannot see an IUP)(2, 3)
Inutrauterine pregnancy
Figure 3 – Double ring sign(1)
Figure 4 – Double ring sign(4)
Figure 5 – Fetal pole(1)
Mean sac diameter
Crown-rump length (CRL) = Top of skull to base of pelvis(1)
Fetal cardiac activity = proof of live IUP(1)
No definitive intrauterine pregnancy (NDIUP) (2)
DDx for NDIUP(2):
Threatened abortion: abnormal bleeding during pregnancy; normal IUP on US(3)
Inevitable abortion: vaginal bleeding with open os; normal IUP or product of conception (POC) near cervix on US(3)
Incomplete abortion: open os with retained POC; US shows anything from debris to embryo; abnormal uterine contents confirms dx(1)
Complete abortion: empty uterus + positive βHCG +/- closed os; same findings as for ectopic therefore requires formal US + serial βHCG(1)
Ectopic pregnancy (3)
Corpus luteal cyst(2,3)
Blighted ovum (anembryonic pregnancy)(1,2)
Molar pregnancy (1,3)
Figure 7 – Extrauterine pregnancy(1)
Figure 8 – Normal myometrial mantle(1)
Figure 9 – Cornual ectopic pregnancy(1)
Figure 10 – Clinical application(2)
References:
Dr. Kyle Traboulsee, PoCUS Fellow
Reviewed by Dr. David Lewis
Copyedited by Dr. Mandy Peach
Background:
Often hypotensive, or acutely dyspneic patients, present to the emergency department in significant distress, and emergency physicians must work quickly to evaluate, stabilize, and treat these patients. In the past, determining whether there was a cardiac etiology to these presentations often relied solely on history, physical exam, and varies biochemical markers. Point-of-care ultrasound has increasingly been adopted as a tool to assess cardiac function, and specifically left ventricular ejection fraction (LVEF). Different methods can be used to estimate LVEF (such as “eyeballing”, and the Simpson method), but they can have large inter-reader variability, and require significant cardiac PoCUS experience. E-point septal separation is a measurement of how close the anterior mitral valve leaflet comes towards the interventricular septum and has been shown to be a quick and easy method for estimating LVEF. (1)(2)
Anatomy/pathophysiology
Blood flow is determined by pressure gradients, where blood will travel from areas of high pressure to low pressure. Such a pressure gradient exists between the left atrium and left ventricle. During diastole, the left ventricle relaxes, and the intraventricular pressure decreases until the pressure falls below that of the left intra-atrial pressure. When the left atrial pressure exceeds the left ventricular pressure, the mitral valve opens, and blood passively flows from the high(er) pressure atrium to the lower pressure ventricle. This occurs early in diastole, and the flow of blood from atrium to ventricle is further assisted by an atrial contraction (termed atrial kick) later in diastole. In a healthy individual the atrial-ventricular (A-V) gradient is sufficient to open the mitral valves and bring the anterior mitral leaflet in proximity (or contact) with the intraventricular septum. (1)(2)(3)
In the case of reduced LVEF, the diastolic pressure inside the left ventricle increases due to a decreased ability to eject blood during systole. This can occur due to several reasons, but often result in left ventricular dilation to compensate and preserve LVEF. As LVEF decreases, the ventricular diastolic pressure increases, and the atrial-ventricular (A-V) gradient decreases, leading to a decreased flow rate from atrium to ventricle during diastole, and thus a decreased mitral valve opening. That, paired with LV dilation, leads to an increased (measurable) distance between the anterior mitral valve leaflet and the intraventricular septum during diastole, which can be used as a surrogate marker for left ventricular function. (1)(2)(3).
PoCUS Technique
The E-point septal separation measurements will be made using a parasternal long axis (PLAX) view
Obtaining PLAX view
Steps:
The optimal PSL image includes the left ventricle (LV) in continuity with the aortic outflow tract. The right ventricle will be near field, the left atrium far field, and the mitral valve, aortic valve, and LV cavity are in between (in the middle of the field). The apex of the left ventricle will be screen left. (4)(5).
Parasternal long axis view- probe orientation (6) Parasternal long axis view-anatomy (7)
Parasternal long axis view: normal (own image)
EPSS measurements
EPSS measurements are commonly obtained using M-mode.
A normal EPSS measurement with M-mode (8)
PSL: normal EPSS, M-mode (own image)
An abnormal EPSS measurement with M-mode (8)
EPSS measurements can alternatively be measured in B mode
PSL-Poor mitral valve opening (own image)
PSL view- abnormal EPSS measurement in B mode (9)
Interpretation
An EPSS < 7mm is considered normal
An EPSS >7 mm has been suggested as 87% sensitive and 75% specific for an EF <50% (10)
Another study suggested that an EPSS >7 mm was 100% sensitive and 51.6% specific for an EF<30% (11).
One MRI study came up with the following formula to calculate EF (4):
EF=75.5 – (2.5 x EPSS in mm)
Pitfalls
Although a quick and relatively simple surrogate measurement for LVEF, there are some patient populations and situations in which EPSS may give in inaccurate estimate of cardiac function. Patients with mitral stenosis may have poor valve opening, leading to a high EPSS, in the context of an otherwise normally functioning left ventricle. Patients with aortic regurgitation may also have poor anterior mitral valve leaflet motion, and thus have a falsely high EPSS. For these reasons, it would be reasonable to apply color doppler across the mitral and aortic valves to assess for signs of regurgitant jets, as well as close assessment of the valves for signs of calcification. Off-axis measurement, regional wall motion abnormalities, and left ventricular hypertrophy may also result in false interpretations concerning LVEF (1)(3)(4).
Bottom line
E-point septal separation is a relatively easy and reproducible technique that can be used to generate a quick estimation of left ventricular function and can help point towards a cardiac etiology in the undifferentiated patient. It is important to keep in mind factors (as discussed) that may lead to false EPSS interpretations, and EPSS results should not preclude a more global cardiac assessment.
References:
Victoria Mercer, Clinical Clerk 3, DMNB
Reviewed and Copyedited by Dr. Mandy Peach
Rib fractures are a frequent presentation in the ED, occuring in approximately 10% of all injured patients with the primary causes being blunt chest trauma and MVAs(1,2). The mainstay of treatment for rib fractures is analgesic control(1). When pain cannot be adequately managed, the patient is at a heightened risk of hypoventilation due to decreased thoracic mobility and secretion clearance, predisposing the patient to significant atelectasis(1,2).
Historically the pain from rib fractures has been managed with acetaminophen or NSAIDS and if these do not sufficiently alleviate the pain, opioids are used(1,3). Unfortunately, these methods often do not provide adequate pain control or in the case of opioids, come with a myriad of side effects such as nausea, vomiting, constipation, respiratory depression and the potential for dependency and abuse (1,4).
An alternative to traditional methods include regional techniques such as paravertebral or epidural nerve blocks. These interventions have been shown to effectively control pain in rib fractures(3,4). The downside to these interventions include being technically challenging and time consuming with significant complication risks and contraindications such as coagulation disorders (1,3).
The solution? A serratus anterior block
An ultrasound guided blockade of the lateral cutaneous branches of the thoracic intercostal nerves was first described by Blanco et al. in 2013 for patients following breast surgery to manage their postoperative pain(5). This procedure has been adopted by many emergency departments for its convenience and practicality compared to epidural or paravertebral nerve blocks(3).
Serratus anterior blocks are less invasive and considerably more practical in the ED setting, providing paresthesia to the ipsilateral hemithorax for 12-36 hours (6).
The only absolute contraindications are patient refusal, allergy to local anesthetic and local infection(1).
Complications of a serratus anterior block include pneumothorax, vascular puncture, nerve damage, failure/inadequate block, local anesthetic toxicity and infection(1).
Serratus anterior blocks are only effective for the anterior two-thirds of the chest wall (3).
Figure 1. Ultrasound image of serratus anterior muscle and surrounding tissues with superficial or deep needle guides. Image from Thiruvenkatarajan V, Cruz Eng H, Adhikary SD. An update on regional analgesia for rib fractures. Current Opinion in Anaesthesiology. 2018;31(5):601–607.
How do you do it?
The procedure is usually performed with the patient laying supine however the patient could also lay in a lateral decubitus position (1,3). Using a high frequency linear ultrasound probe (6-13MHz), identify the serratus anterior and latissimus dorsi muscles over the fifth rib in the mid-axillary line(1,3). Using an in-plane approach, insert the needle either superficial or deep to the serratus anterior and confirm correct needle placement by visualizing anaesthetic spread via ultrasound(1,3). According to May et al., superficial spreading tends to have a longer lasting analgesic effect(1). Place and secure a catheter to infuse the remainder of the bolus(1,3). Thiruvenkatarajan et al. recommend a bolus of 40ml of 0.25% levobupivacaine and a 50mm 18G Tuohy catheter needle(3).
See this excellent review by Dr. David Lewis on identifying rib fractures and their complications using ultrasound (start 3:08) as well as a review of the block and procedure (start 8:00)
References
PoCUS Fellow
Dalhousie University Department of Emergency Medicine
Dr. Melanie LeClerc
PoCUS Fellow
Dalhousie University Department of Emergency Medicine
Two- plane point of care ultrasonography helps in the differential diagnosis of pulled elbow
Dr. Melanie Leclerc, CCFP-EM
MSK PoCUS Fellow
Dalhousie University Department of Emergency Medicine
Reviewed & Edited by Dr David Lewis (@e_med_doc)
All case histories are illustrative and not based on any individual
A 37 year old, right hand dominant, carpenter presents to your local ED with a complaint of right wrist pain. He was on a step-stool and lost his balance earlier today. He fell landing on his outstretched arm and had an acute-onset of radial-sided wrist pain. He denies any other injury. There are no neurologic complaints.
On exam, there is no visible deformity. The skin is closed and there is some swelling noted. The patient is tender over the anatomic snuff box as well as volarly over the scaphoid. There is pain noted with axial loading of the thumb. There is no other tenderness. ROM is within normal limits. The limb is distally neurovascularly intact.
X-rays are normal.
An occult scaphoid fracture is suspected. At this institution, patients with suspected occult scaphoid fracture are placed in a thumb spica splint and referred to the local hand surgeon to be seen in ~10-14 days for repeat assessment and X-ray.
Can Point of Care Ultrasound change this traditional “splint and wait” patient pathway?
Scaphoid fracture is a common presentation to the Emergency Department accounting for approximately 15% of all wrist injuries and 70% of carpal fractures. Up to 30% of the time, radiographs at initial presentation appear normal making fracture a commonly missed injury for Emergency physicians. A failure to recognize this injury can lead to chronic pain and functional impairment for patients. Particularly, fractures of the proximal pole (most distant to the blood supply) can lead to avascular necrosis (AVN) at high rates. Non-union can lead to scaphoid non-union advanced collapse (SNAC wrist) which can perpetuate further degenerative changes throughout the carpus. This can cause a significant impact on quality of life and occupation. Early detection of fracture could expedite fixation and possibly results in better outcomes. Further study in this area is needed.
The scaphoid bone lies in the radial aspect of the proximal carpal row. It’s unique shape (“twisted peanut”), lends to easy recognition. It articulates proximally with the distal radius, distally with the trapezium, and on its’ ulnar aspect with the lunate to form the scapho-lunate interval. The blood supply to the scaphoid is unique in that the majority of it is retrograde. The dorsal carpal branch of the radial artery supplies the bone from distal to proximal. A small proportion of the blood supply originates at the proximal end. The boundary between the two supplies creates a “watershed” area prone to non-union and AVN.
Scaphoid fractures are classified by location. These regions are the proximal, middle and distal thirds which account for 20%, 75%, and 5% of the fractures respectively. The stability of fractures is determined by the displacement (>1mm) and angulation (scapholunate angle >60 and radiolunate angle >15). The Hebert Classification as endorsed by Traumapedia can be found below.
Imaging of these suspected injuries varies. Traditionally serial X-rays were used, but have been found to be poorly sensitive even several weeks after injury. Bone scan has also been used as an alternative due to it’s high sensitivity, but has poor specificity and provides no further information regarding the nature of the fracture. CT is relatively sensitive and specific and provides information for pre-operative planning. MRI is considered the gold standard, but is difficult to obtain in a timely manner in Canada.
Bäcker HC, Wu CH, Strauch RJ. Systematic Review of Diagnosis of Clinically Suspected Scaphoid Fractures. J Wrist Surg. 2020 Feb;9(1):81-89. doi: 10.1055/s-0039-1693147. Epub 2019 Jul 21. PMID: 32025360; PMCID: PMC7000269.
Scaphoid cortical disruption was visualized using PoCUS. After discussion with the hand surgeon, a CT Scan of the wrist was performed which confirmed a minimally displaced waste fracture of the scaphoid. The patient was splinted and seen the next day in clinic for discussion regarding operative management.