Category: Journal Club

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Ultrasound Guided Catheterization of the Radial Artery

Background

Arterial catheterization (the radial artery being the most common site)  is often performed in critically ill patients for hemodynamic monitoring and serial blood gas sampling, and is a core skill for critical care and emergency providers alike. While ultrasound guidance has become standard of care for  central venous catheterization, this is still not common practice for radial artery catheterization. In this critically ill patient population, there are often patient specific factors that make this procedure difficult using the palpation method, including hypotension, edema and obesity. Frequently, the palpation method requires multiple attempts which can result in arterial vasospasm, making further attempts even more difficult. This review article investigates whether their is a role for the addition of ultrasound guidance to radial artery catheterization. 

Ultrasound-Guided Catheterization of the Radial Artery 

Figure 1: Flow diagram of study identification, inclusion, and exclusion

Figure 1: Flow diagram of study identification, inclusion, and exclusion

Figure 2: Summary of RCTs of ultrasound-guided arterial catheterization

Figure 2: Summary of RCTs of ultrasound-guided arterial catheterization

Figure 3: Effect of ultrasound-guided catheterization of first attempt success

Figure 3: Effect of ultrasound-guided catheterization of first attempt success

Figure 4: Effect of ultrasound guided catheterization on first attempt success

Figure 4: Effect of ultrasound guided catheterization on first attempt success

Clinical Question

Does ultrasound guidance for radial artery catheterization improve first attempt success compared to the palpation method? 

Methods & Study Design

  • Design
    • Systematic Review and Meta-analysis of Randomized Controlled Trials
      • Article selection
        • Databases searched: EMBASE, CENTRAL, and Medline from inception through February 23, 2010
        • Critical care conference abstracts reviewed from 2005-2009
        • Experts in the field also contacted to seek additional articles
        • The methodologic quality of selected trials was appraised by two independent reviewers using the Jadad criteria
  • Population (See Figure 1)
  •  Heterogenous population of adults and pediatric patients in different clinical settings
  • Inclusion criteria
    • Randomized control trials comparing 2-D ultrasound guidance technique to traditional palpation technique for radial artery catheterization
  • Exclusion criteria
    • Trials evaluating use of doppler ultrasonography, marking techniques, or catheterization of arteries other than the radial artery were excluded
  • Intervention
    • Ultrasound guided radial artery catheterization
  • Outcomes
      • First-attempt success for radial artery catheterization

Results

    • A total of 4 RCTs were included in the final meta-analysis. Individual characteristics can be viewed in figure 2.
    • Pooled Findings
      • The pooled relative risk for ultrasound guided techniques was 1.71 (95% CI, 1.25-2.32). The forest plot can be seen in figure 3 with data provided in figure 4.

Strengths & Limitations

  • Strengths
    • Comprehensive literature search
    • Included only RCTs comparing traditional palpation technique to ultrasound guided technique for radial artery catheterization
    • Adequate sample size obtained which reached statistical significance with respect to outcome
    • Studies independently reviewed by two reviewers for inclusion in meta-analysis
  • Limitations
    • The patient populations were very heterogenous among RCTs (1 adult surgery population, 1 infant neurosurgery population, 1 adult ED population, 1 pediatric surgery population)
    • The operator populations were very heterogeneous among RCTs (anesthesia attendings/residents, emergency physicians, pediatric trainee and consultant anasthesiologists)
    • Lack of blinding

Author's Conclusions

 "Our meta-analysis clearly demonstrated a 71% increase in the likelihood of first-attempt success when using ultrasound guidance for radial artery catheterization."

Our Conclusions

Radial artery catheterization is fraught with error and barriers to success. Often this procedure will be performed in sick patients, with the operator encountering obesity, edema, and shock, all of which can contribute to difficulty palpating the radial pulse. Furthermore, even if the pulse is palpated, this can be unreliable at predicting underlying anatomy. Ultrasound allows direct visualization of the radial artery, including depth, diameter and surrounding structures, and allows for ongoing needle guidance. While not studied, in my personal experience I have also noted numerous occasions where the only sign of successful radial artery catheterization was direct visualization of the catheter tip in the radial artery (i.e. no blood seen in flash chamber) on ultrasound. If the standard palpation method was used, this would lead to a failed attempt.

It has become clear in many other instances that ultrasound adds safety and success to procedures routinely performed in the emergency department including: central venous access, thoracentesis, paracentesis, peripheral nerve blocks and arthrocentesis (of specific joints). This study allows us to confidently add radial artery catheterization to the list. While the patient population and operators in the study discussed are heterogeneous, it is reasonable to assume that emergency medicine providers who have experience with ultrasound guided procedures, will perform just as well, if not better than the study findings.  This generalization assumes ultrasound guided procedure experience and those without this experience may not show a benefit over the traditional palpation method for radial artery catheterization. This study does not mean that the palpation method is obsolete, rather, it suggests that ultrasound is a useful adjunct and likely adds success in patients with risk factors for difficult radial artery catheterization such as obesity, hypotension, edema or a difficult to palpate pulse.

The Bottom Line

Ultrasound guidance for radial artery catheterization shows a higher first-attempt success rate compared to the standard palpation method and should be considered by operators with other procedural ultrasound guidance experience. 

Authors

This post was written by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Shiloh AL, e. (2018). Ultrasound-guided catheterization of the radial artery: a systematic review and meta-analysis of randomized controlled trials. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 13 January 2018, from https://www.ncbi.nlm.nih.gov/pubmed/20724734

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Review of Lawsuits Related to Point of Care Emergency Ultrasound Applications

Background

Point-of-care (POC) ultrasound has become heavily integrated into clinical practice in emergency departments (ED). Ultrasound training is now standard in emergency medicine (EM) residency programs and most emergency physicians are able to independently perform and interpret bedside ultrasounds exams. With the rise in use of POC ultrasound by emergency physicians, there is an accompanying theoretical increase in malpractice risk. Malpractice risk can potentially arise from failure to perform an adequate study, failure to interpret findings accurately, or misdiagnosis. This increased liability has prompted some emergency physicians to avoid POC ultrasound in their own practice to decrease their personal risk or transfer risk to consulting services, such as radiology. However, the opposite argument could also be made that failure to incorporate ultrasound into one’s emergency medicine practice can leave clinicians susceptible to legal action as well. This study aims to build on the work of Blavais et al, which revealed that from 1987-2007 there was only one identifiable malpractice lawsuit associated with POC ultrasound. Given the increased use of POC ultrasound since the prior study, this article aims to further characterize the nature of malpractice lawsuits associated with POC ultrasound in more recent years.

Review of lawsuits related to POC emergency ultrasound applications

Clinical Question

With the increased use and scope of practice of POC ultrasound in EM, is there an associated increased  legal risk to emergency physicians performing POC ultrasound?

Methods & Study Design

  • Design
    • Retrospective review of Westlaw database for reported decisions in state and federal malpractice cases involving POC ultrasound
      • Westlaw database include state and federal case law and statutes, and public records
  • Population
    • Published case law in the US from Jan 2008 – Dec 2012 in the Westlaw database
  • Inclusion criteria
    • Cases were included if:
      • Physician was accused of misconduct
      • Patient encounter was in ED
      • Interpretation or failure to perform ultrasound was discussed to any degree
      • Ultrasound application was within ACEP ultrasound core applications (trauma, intrauterine pregnancy, AAA, cardiac, biliary, DVT, urinary tract, soft tissue/MSK, thoracic, ocular, procedure)
      • Ultrasound exam performed or ordered through a radiology department was within scope of ACEP core emergency ultrasound applications
  • Exclusion criteria
    • There were no specific exclusion criteria. However, cases settled out of court, cases with unreported decisions, and cases not publically available (private negotiations, arbitration, sealed records, etc) were not available for analysis through the Westlaw database.
  • Intervention
    • Westlaw database was reviewed for published case law (federal and state) in the US from Jan 2008 – Dec 2012
    • Search terms included “ultrasound”, “sonography”, “emergency”, “physician”, “doctor”
    • Emergency physicians with emergency ultrasound fellowship training reviewed case records that were identified via search. Specific case information was collected. Any discrepancies were discussed between the two reviewers to reach a consensus.
  • Outcomes
      • The follow case information was collected:
        • Basic clinical narrative of case
        • Exam type involved
        • Department that performed exam
        • Broad category of type of allegation (i.e. misdiagnosis, failure to interpret, failure to perform, failure to perform in timely manner)

Results

    • 120 records matched initial search criteria; 7 of these matched inclusion criteria
      • 2 out of 7 were reviewed and found to be outside the scope of ACEP core ultrasound applications
    • 5 identified malpractice cases relating to POC ultrasound in the ED
      • No cases resulted from misdiagnosis with POC ultrasound or failure to interpret POC ultrasound
      • All cases involved failure to perform a complete ultrasound study or failure to perform in a timely manner
      • Most common exam type was DVT study
      • Majority of cases involved patient death

Strengths & Limitations

  • Strengths
    • Provides valuable data on legal landscape of POC ultrasound
    • Study was designed to identify cases where emergency physicians not only performed but could have performed an ultrasound exam. This allows for potential assessment of “deferred risk”.
  • Limitations
    • Small n – Small number of cases limits ability to approximate any measure of risk to emergency physicians using POC ultrasound
    • Selection bias – Cases settled out of court, cases with unreported decisions, cases not publically available (private negotiations, arbitration, sealed records, etc) not included in Westlaw database
    • Limited assessment of other factors associated with each case: emergency physician ultrasound skills, access to ultrasound, level of facility support, barriers to perform ultrasound, medical decision making process

Author's Conclusions

“From 2008 to 2012, the Westlaw database reported no judicial decisions against an emergency physician performing POC ultrasound. The database reports five cases related to failure to perform an ultrasound examination that was within the scope of ACEP core emergency ultrasound applications in a timely manner. Further analyses using other legal data sources and insurance claim data are desired and further work is necessary to confirm these preliminary findings.”

Our Conclusions

This study provides reassuring evidence that emergency physicians are not significantly burdened by malpractice lawsuits relating to POC ultrasound use in their clinical practice. In a comprehensive search of publicly available federal and state US malpractice claims, only five cases were found to be associated with POC ultrasound. However, this number must be interpreted with caution. Rubin et al demonstrated that a very small percentage of paid malpractice claims in the US are judged in court (3.1%) while the majority are settled outside (96.9%). The Westlaw database used in this study was able to access only publicly available case data, or cases that were judged in court. Thus, it is difficult to draw generalizable conclusions about the legal risks associated with POC ultrasound from this study. Overall, this study reveals that within publicly available malpractice claims data, lawsuits relating to POC ultrasound are in the minority. While there is legal risk associated with use and failure to use available diagnostic modalities, emergency physicians should feel encouraged to incorporate POC ultrasound exams into their clinical practice.

The Bottom Line

Though the data is limited, there is some reassuring evidence that there is no significant legal burden associated with POC ultrasound used within the scope of ACEP core emergency ultrasound applications. Emergency physicians should continue to incorporate POC ultrasound into their clinical practice.

Authors

This post was written by Neha Chandra, MS4 at University of California, San Diego. It was reviewed by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

      1. Rubin, Jessica B., and Tara F. Bishop. "Characteristics of paid malpractice claims settled in and out of court in the USA: a retrospective analysis." BMJ open 3.6 (2013): e002985.
      2. Stolz, Lori, et al. "A review of lawsuits related to point-of-care emergency ultrasound applications." Western Journal of Emergency Medicine 16.1 (2015): 1.
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The effect of vessel depth, diameter, and location on US guided peripheral intravenous catheter longevity

Background

Nearly 30% of all patients who visit the ED in the US each year will require venous access. Bedside ultrasound-guided peripheral IVs (USGPIV) offer an alternative to central venous cannulation and external jugular cannulation for patients in which PIV access cannot be obtained, thereby reducing the risks of infection and the need for additional resources that are associated with the aforementioned procedures. The downside to USGPIVs lies in the longevity of this method of venous access, which introduces complications such as extravasation, tissue necrosis and disruption of access.  Failure rates are high, with 8% of them failing within the first 8 hours, and 47% failing within the first 24 hours. The authors of this weeks article speculate that this is due to the nature of the vessels targeted by ultrasound (US), being that they are often deeper and smaller veins in locations that are otherwise difficult to access without specialized imaging. This article will explore the influence of various vessel characteristics on the success and longevity of the USGPIVs, including vessel depth, diameter, and location.

The effect of vessel depth, diameter, and location on US guided peripheral intravenous catheter longevity

Clinical Question

How do specific characteristics of a vessel determine the success and longevity of a USGPIV?

Methods & Study Design

  • Design
    • A retrospective chart review of a previously gathered database of difficult intravenous access (DIVA) patients who underwent USGPIV placement in the ED
    • Data included images and measurements of the vessel’s depth, diameter and location as well as survival time of the IV
  • Population
    • Urban tertiary care center with a 4-yr EM residency and an US fellowship
    • Study period: Dec 2007-May 2008
  • Inclusion criteria
    • All DIVA patients: A DIVA patient is defined as someone with 2 failed peripheral IV attempts or a history of DIVA with inability to visualize or palpate a target vein on physical exam
    • DIVA patient must have underwent successful USGPIV placement in ED
  • Exclusion criteria
    • There were no specific exclusion criteria however patients were excluded for several reasons:
      • 18 for inability to establish USGPIV using study protocol
      • 12 for lack of charting to accurately determine time of IV removal
      • 2 for failure of consensus of at least 2 of the 3 blinded independent chart reviewers on timing or outcome of IV
  • Intervention
    • USGPIVs were placed by 2 PGY-2s, 1 PGY-3, and 1 US fellow, all met ACEP guidelines (at least 10 USGPIVs previously performed)
      • Successful IV placement was defined as aspiration of 5 mL of blood and ability to flush the line without resistance
      • Only 20-gauge, 48-mm-long (Angiocath Autoguard;BD Medical Systems, Sandy, UT) catheters were used for USGPIV placement
      • During USGPIV placement, vessels were measured for depth and diameter, and location was noted on a diagram of the upper extremity
  • Outcomes
      • Failure rate of USGPIV based on depth, diameter, and location
        • 2 blinded independent chart reviewers followed successfully placed USGPIVs for 48 hours or until failure, whichever came first
        • Failures were defined as IVs that infiltrated, dislodged, stopped working or were discontinued prematurely
        • IVs removed on patients that no longer required access were not considered failures

Results

  • Calculated USGPIV survival curves for vessels at given depths and location from Fields et al.
    • Statistical Analysis
      • Vessel depth divided into 3 zones: shallow (0.4 cm), intermediate (0.4-1.19 cm), and deep (≥1.2 cm); Intravenous diameter was divided into 4 groups (<0.3, 0.3-0.39, 0.4-0.49, and ≥0.5 cm);
      • Vessel location was divided into proximal (brachial region) and distal (antecubital fossa, forearm, or hand veins).
      • Kaplan-Meier estimator was used to measure time-to-failure and remove potential confounder of IVs that were removed for discharge or no longer needed
    • Findings
      • At 48 hrs, 48 (32%) had failed because of dislodgment, infiltration, or patient discomfort
        • 20 (42%) infiltrated
        • 11 (23%) dislodged
        • 16 (33%) were not flushing
        • 1 removed for discomfort
        • 36 (24%) were removed for routine reasons
        • 67 (44%) were still in place and without incident
        • There was no difference in patient characteristics of IVs that failed vs. those that did not fail
      • Kaplan-Meier Survival Analysis 
        • Depth: Survival probability excellent (1.00) for shallow vessels, moderate (0.62) for intermediate vessels, poor (0.29) for deep vessels STRONGEST PREDICTOR
        • Location: antecubital fossa or forearm associated with improved survival when compared with proximal placement in brachial or basilic vein (0.93 vs. 0.71)
        • Diameter: no significant difference
        • For each increase of 0.2 cm in depth, odds of failure at 48 hrs increases by hazard ratio of 1.36
        • Placement in proximal vs. distal location increases odds of failure by hazard ratio 2.76

Strengths & Limitations

  • Strengths
    • No difference in patient characteristics between failed and successful USGPIVs
    • Recruited difficult IV access patients from urban academic tertiary ED which is likely representative of true difficult access patient population and can be generalized to other EDs
    • 2 independent reviewers used for retrospective chart review
  • Limitations
    • Outcome variable (survivability) was gathered retrospectively; potential bias in rapid realization of IV failure and clear documentation
    • Possible that failed catheters were documented as “removed” because they were no longer needed or another access was obtained
    • Did not account for certain factors: nature of the infusion, how often IV accessed, movement of extremity, use of fixation device
    • Only assessed using 20-gauge, 48-mm IV
    • Small group of sonographers performed data collection, they may be more skilled than general population of emergency physicians

Author's Conclusions

“Ultrasound provides a useful rescue method for establishing IV access in patients with DIVA. The current study reveals 2 factors that significantly affect the durability of these IVs— depth and location. Using a 48-mm catheter, vessels of 1.2 cm or more deep have a high likelihood of USGPIV failure and should only be cannulated when other options are not available. Vessels of less than 0.4 cm deep yield the best USGPIV longevity. Forearm and antecubital sites are more enduring than those in the upper arm. Understanding of these associations will help the sonologist select the optimal vessel for successful USGPIV cannulation and longevity.”

Our Conclusions

Depth should be the primary consideration when selecting a vessel for USGPIV access. Due to high immediate failure rates, vessels of 1.2 cm deep or more deep should be avoided and other means of obtaining venous access should be considered. Providers should also take into consideration the location of IV placement. If it is anticipated that a patient will require IV access for longer than the immediate stay in the emergency department, then proximally-located IVs should be avoided given their high failure rate at 18 hours. This failure may be explained by the fact that proximal vessels are located closer to the axilla and usually embedded in looser skin containing more subcutaneous fat with greater potential for dislodgment upon movement of the extremity. Therefore, providers should consider how long the patient will be requiring access as well as how often the patient will be required to move the extremity in making decisions regarding venous access.

The Bottom Line

USGPIVs that are placed in more superficial (<1.2 cm) and distal (forearm/antecubital space) veins have a significantly higher likelihood of survival at 48 hours and these factors should strongly be considered when evaluating for a target for IV placement.

Authors

This post was written by Courtney Shay, MS4 at George Washington University. It was reviewed by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Fields JM, e. (2017). The effect of vessel depth, diameter, and location on ultrasound-guided peripheral intravenous catheter longevity. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 10 November 2017, from https://www.ncbi.nlm.nih.gov/pubmed/22078967

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Focused Transesophageal Echocardiography by Emergency Physicians is Feasible and Clinically Influential

Background

Cardiac ultrasound is frequently used in the emergency department (ED) to effectively identify  pericardial effusion, differentiate causes of shock, assess left ventricular function, and guide cardiopulmonary resuscitation (CPR). However, cardiac ultrasound employed in the ED is usually transthoracic echocardiography (TTE) as opposed to transesophageal echocardiography (TEE). TTE can often be limited, especially in critically ill patients and patients with high BMI. TEE offers the ability to reliably obtain continuous high-quality images that can be performed without interrupting CPR. Despite this, TEE is not often employed in the ED due to a variety of factors, including transducer cost, invasiveness, physician training, and hospital culture.

Focused Transesophageal Echocardiography by Emergency Physicians is Feasible and Clinically Influential: Observational Results from a Novel Ultrasound Program

 

Clinical Question

Is TEE performed by emergency medicine trained  physicians, in the emergency department setting, feasible and does it provide clinical utility?

Methods & Study Design

  • Design
    • Retrospective Review
  • Population
    • Study performed during a TEE in the ED pilot program by an academic emergency medicine program comprising 2 separate EDs, one of which is a regional trauma center.
    • All patients who underwent TEE in the ED during the 2-year program period were included.
  • Exclusion criteria
    • None
  • Intervention
    • TEE was performed on critically ill, intubated patients. Most commonly, the mid-esophageal 4-chamber view, followed by the transgastric short axis, mid-esophageal long axis, and bicaval views  were obtained.
  • OutcomesThe clinical impact of TEE, divided into two categories:
      • Diagnostic influence on clinical decision making
      • Therapeutic influence on procedures, medications, fluids, and CPR

Results

    • 54 TEE exams performed with 100% probe insertion success rate
      • 83% on first attempt
      • 11% required multiple attempts
      • 6% required use of a laryngoscope
      • 98% of exams produced images that were interpretable by the operator
    • TEE was diagnostically influential in 78% of cases
      • Excluded cardiac cause of arrest (56%)
      • Identified depressed left ventricular function (15%)
      • Identified hypovolemia (13%)
      • Identified regional wall motion abnormalities (6%)
      • Identified aortic dissection (4%)
    • TEE was therapeutically influential in 67% of cases
      • Influenced changes to CPR (43%)
      • Directed cessation of resuscitation (30%)
      • Guided hemodynamic support (26%)
    • No major adverse effects from probe placement identified

Strengths & Limitations

  • Strengths
    • TEE exams were performed successfully by 14 different emergency physicians at 2 separate sites after only 4 hours of training, which demonstrated well the feasibility of TEE use in the ED on a more widespread basis.
    • Well-described outcomes
  • Limitations
    • Retrospective
    • Relatively small sample size
    • No comparison with TTE

Author's Conclusions

“ED- based TEE showed a high degree of feasibility (98% determinate rate) and clinical utility, with a diagnostic and therapeutic influence seen in the majority of cases. Focused TEE demonstrates the most promise in patients who are intubated and have either undifferentiated shock or cardiac arrest.”

Our Conclusions

This study demonstrates that performing TEE in the ED is both feasible and safe, and can be implemented with limited training of the physician staff. It also shows that TEE does have some clinical utility in the ED, specifically the detection of aortic dissection. However, the most common therapeutic effect noted in the study was the assessment of CPR quality, which can typically be assessed with less invasive means such as femoral pulse palpation and waveform capnography. The other common findings noted in the study (i.e. depressed ejection fraction, hypovolemia, guidance of hemodynamic support) can typically be assessed with more traditional and less invasive TTE. In order to truly evaluate the utility of TEE in the ED, a prospective study showing a comparison of TEE with TTE, and other less invasive diagnostic modalities, would need to be performed. That being said, having the ability to diagnose aortic dissection at the bedside and to guide resuscitation via direct cardiac visualization during ongoing CPR are important considerations. This is a promising pilot study that opens up the door for further research evaluating the utility of TEE in the ED, however at this point, it is not clear whether it will perform better than traditional TTE and other clinical adjuncts in both diagnostic and therapeutic abilities.

The Bottom Line

Performing TEE in the ED is both feasible and safe, and does provide useful clinical information. However more studies are required in order to assess the true clinical utility of this modality.

Authors

This post was written by Toby Matt, MS4 at UCSD. It was reviewed by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Arntfield R, e. (2017). Focused Transesophageal Echocardiography by Emergency Physicians is Feasible and Clinically Influential: Observational Results from a Novel Ultraso... - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 30 October 2017, from https://www.ncbi.nlm.nih.gov/pubmed/26508495
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Variability in Interpretation of Cardiac Standstill Among Physician Sonographers

Background

The use of point-of-care echocardiography to inform termination or continuation of cardiopulmonary resuscitative efforts remains controversial [1,2]. Current understanding of its utility in prognostication is limited by varying definitions of cardiac activity. Definitions of cardiac standstill range from absence of “organized contractile activity (nonfibrillating) with a decrease in chamber size” to absence of “any visible movement of the myocardium, excluding movement of blood within the cardiac chambers or isolated valve movement” to absence of “any detected atrial, valvular, or ventricular motion within the heart” [3-5]. Without a consistent definition of cardiac standstill, it is difficult to interpret studies reporting conflicting resuscitation outcomes in cardiac arrest.

Variability in Interpretation of Cardiac Standstill Among Physician Sonographers

Clinical Question

What is the interrater reliability among providers in classification of cardiac standstill in point-of-care echocardiography?

Methods & Study Design

  • Design
    • Cross-sectional convenience sample survey
  • Population
    • Eligible: Residents, fellows, and faculty practicing in emergency medicine, critical care, or cardiology in attendance at one of six weekly emergency medicine (EM) conferences held at the following locations:
      • Icahn School of Medicine at Mount Sinai
      • Beth Israel Medical Center
      • St. Luke’s-Roosevelt Hospital
  • Exclusion criteria
    • Providers who had previously participated at a prior conference
  • Intervention
    • Participants were presented with the following clinical scenario: “55-year-old man in cardiac arrest who remains pulseless after 20 minutes of CPR”
    • Participants were shown 15 clips (6 seconds each, looped for 20 seconds total) presenting a variety of sonographic features
    • Asked to identify presence or absence of cardiac activity
    • Responses transmitted via remote polling devices
    • No definition of cardiac activity was provided
  • Outcomes
    • Primary: interrater reliability in interpreting cardiac standstill (Krippendorff’s alpha coefficient)
    • Secondary: subgroup analyses by specialty, training level, and self-described point of care (POC) ultrasound experience

Results

    • 127 participants (majority EM residents with basic ultrasound skills)
    • Overall moderate agreement with respect to identifying cardiac standstill (alpha 0.47)
    • Clips with stronger agreement:
      • No myocardial contraction
      • Myocardial contraction
      • Strong myocardial contraction
    • Clips with poorer agreement:
      • Valve flutter
      • Mechanical ventilation
      • Weak myocardial contraction
    • Moderate agreement across all training levels and self-reported ultrasonographic skill levels

Strengths & Limitations

  • Strengths
    • All participants saw the same clips
    • Response time limited (similar to clinical practice)
  • Limitations
    • Bias: recruitment from academic conferences
    • Majority with no or basic self-reported ultrasonographic skill level
    • Reported discussion among participants throughout survey

Author's Conclusions

“Our results support the possibility that previous studies have been subject to variability in the interpretation of cardiac standstill.”

Our Conclusions

We agree with the authors’ conclusions that there appears to be substantial variability in the interpretation of cardiac standstill. This study highlights a weakness in the current literature examining the utility of POC echocardiography used during resuscitation futility assessment. While this study does not provide data on clinical outcomes of standstill misclassification, it identifies a potential weakness in the available research. It is difficult to interpret studies reporting outcomes after standstill (such as meaningful survival) when the predictor is not consistently identified.

As a follow-up study, it would perhaps be interesting to see how the interrater reliability changes when participants are provided with a clear definition of cardiac standstill. Does the variability persist even with a uniform definition? If this improves interrater reliability it would provide additional support for the need for a consensus definition across future studies.

The Bottom Line

There is significant variability in classification of cardiac standstill among providers. A uniform definition of standstill may reduce this variability and aid in the interpretation of studies reporting conflicting outcomes after cardiac arrest.

Authors

This post was written by Carly Dougher, MS4 at UCSD. It was reviewed by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Blyth, L., Atkinson, P., Gadd, K. & Lang, E. Bedside Focused Echocardiography as Predictor of Survival in Cardiac Arrest Patients: A Systematic Review: Echocardiography in Cardiac Arrest. Acad. Emerg. Med. 19, 1119–1126 (2012).
    2. Cohn, B. Does the Absence of Cardiac Activity on Ultrasonography Predict Failed Resuscitation in Cardiac Arrest? Ann. Emerg. Med. 62, 180–181 (2013).
    3. Schuster, K. M. et al. Pulseless Electrical Activity, Focused Abdominal Sonography for Trauma, and Cardiac Contractile Activity as Predictors of Survival After Trauma: J. Trauma Inj. Infect. Crit. Care 67, 1154–1157 (2009).
    4. Gaspari, R. et al. Emergency department point-of-care ultrasound in out-of-hospital and in-ED cardiac arrest. Resuscitation 109, 33–39 (2016).
    5. Kim, H. B., Suh, J. Y., Choi, J. H. & Cho, Y. S. Can serial focussed echocardiographic evaluation in life support (FEEL) predict resuscitation outcome or termination of resuscitation (TOR)? A pilot study. Resuscitation 101, 21–26 (2016).
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Right ventricular dilatation on bedside echocardiography performed by emergency physicians aids in the diagnosis of pulmonary embolism

Background

Pulmonary embolism (PE) is a disease entity with a high mortality rate, ranging from 2.5-33%. Frequently, its diagnosis is delayed or frankly missed and often it is only discovered during autopsy. Around 66% of deaths occur during the first hour of presentation and 75% of deaths during the initial hospitalization. The mechanism of morbidity/mortality for PE is thought to be secondary to right ventricle (RV) outflow obstruction, leading to circulatory collapse. Delays in diagnosis have been linked to issues with imaging (wait times, schedules), contrast in the setting of renal impairment, and poor IV access.

In the emergency department, it is not only critical to identify patients with PE, but also to identify those who are at risk for decompensation and poor outcomes. This can be accomplished by evaluating for signs of RV dysfunction which has been associated with RV failure, hemodynamic collapse, and death. Previous studies have shown that right ventricular dysfunction has been found in 27-40% of normotensive patients with PE. Well studied markers of RV dysfunction include elevated biomarkers [1], specific ECG findings (RBBB, tachycardia, S1Q3T3, anterior TWI, ST elevation aVR, atrial fibrillation) [2], and RV dysfunction on echocardiography [3]. While biomarkers and ECG are readily available to emergency providers (EP), these are less specific for the diagnosis of PE and bedside echocardiography may prove to be more useful for evaluation of PE and RV dysfunction.

Right Ventricular Dilatation on Bedside Echocardiography Performed by Emergency Physicians Aids in the Diagnosis of Pulmonary Embolism

Clinical Question

Does evaluation for right ventricular dilation by emergency physicians using bedside echocardiography add diagnostic value in the evaluation for suspected pulmonary embolism? 

Methods & Study Design

  • Design
    • Prospective observational study
  • Population
    • Using a “convenience sample” population of patients who presented to the ED at Boston Medical Center from June 2009 – August 2011, with a moderate to high suspicion (pretest probability) of having a PE.  Wells score ≥2, those receiving PE imaging (CT, angio, V/Q scan), or those who came in with diagnosis of PE.
  • Exclusion criteria 
    • Non-english speakers
    • Prisoners
  • Intervention
    • Transthoracic echocardiography (blinded of confirmatory results) was performed by 4 ED docs, 1 with advanced training in cardiac sonography.  The other 3 had standard 1-month residency rotation in ultrasound and a minimum of 25 cardiac ultrasounds; plus, 10 hours hands-on and 10 hours image review with principal investigator.
    • Data collection
      • 3 views recorded: parasternal short & long axis, and apical 4-chamber, with primary measurement being qualitative assessment of RV size vs. LV size. Normal ratio (0.6:1)
        • Dilation defined as >1:1 RV:LV ratio
        • RV length and diameter or qualitative distension of RV apex adjacent to LV apex also assessed
      • They also recorded: RV function (nl vs. hypokinetic), paradoxical septal motion, and presence of McConnell’s sign.
      • All image reads were reviewed by the PI.
      • ED RAs then used chart review to compare findings to confirmatory imaging
        • PE was categorized as proximal vs distal
        • Disposition of patient was also documented 
  • Outcomes
    • Diagnostic characteristics
      • Sensitivity, specificity, PPV, NPV, positive and negative likelihood ratios
    • Presence of advanced signs of RV dysfunction
      • Right ventricular hypokinesis [qualitatively assessed as normal or hypokinetic], paradoxical septal motion, and McConnell’s sign

Results

    • Final analysis
      • 146 patients included in study
      • 126 with moderate pretest probability
      • 20 with high pretest probability
      • 126 with normal RV:LV ratio, 17 with increased RV:LV ratio
      • 30 had PE, of these 15 also had increased RV:LV ratio
    • Presence of RV dilation test characteristics
      • Sensitivity 50% (95% CI 32% to 68%)
      • Specificity 98% (95% CI 95% to 100%), a positive predictive value of 88%
      • Positive Predictive Value 88%  negative predictive value of 88%
      • Negative Predictive Value 88% (95% CI 83% to 94%).
      • Positive Likelihood Ratio 29 (95% CI 6.1% to 64%)
      • Negative Likelihood Ratio 0.51 (95% CI 0.4% to 0.7%)
      • Good observer agreement 96%, independent 100%

Strengths & Limitations

  • Strengths
    • Good concordance of sens/spec with prior study observations, although higher sensitivity
    • Good intra-observer agreement/reliability
  • Limitations
    • Single location, young population (less chronic diseases leading to RV changes)
    • Operator skill may not generalize to other physicians, other EDs.  PI was very experienced sonographer.
    • Convenience sample leading to possible selection bias.
    • Secondary outcomes under-powered.

Author's Conclusions

The authors conclude that right ventricular dilatation on bedside echocardiography may help emergency physicians rule in pulmonary embolism more rapidly by raising a provider’s index of suspicion before definitive testing. They also note that this evidence supports the concept that patients with a moderate to high pretest probability for pulmonary embolism and a bedside echocardiography result showing right ventricular dilatation should be considered for anticoagulation before definitive testing.

Lastly, they also comment on severity of PE, noting that patients with signs of advanced right ventricular dysfunction on bedside echocardiography (right ventricular dilatation with right ventricular hypokinesis, McConnell’ s sign, or paradoxical septal motion), tends to occur in patients with a larger clot burden who are more likely to be admitted to an ICU setting or have in hospital mortality (though this study was not powered appropriately for this analysis).

Our Conclusions

 We agree with the author's conclusions of this study that EP performed bedside echocardiography is a useful adjunct in the evaluation of suspected PE, both in identification of PE as well as risk stratification. We know that delays in diagnosis/treatment can lead to worse outcomes, however with the ability of EPs to perform bedside echocardiography and identify right ventricular dilation, this may reduce the time to both of these endpoints. It also seems reasonable that in patients who are moderate to high risk for PE, whom have evidence of right ventricular dilation on bedside echocardiography,  be empirically treated with anticoagulation prior to definitive imaging, with the caveat that they have no high bleed risk.

The Bottom Line

Emergency physician performed bedside echocardiography can be used reliably to increase provider's index of suspicion for PE in patients demonstrating RV dilation; however, given its poor sensitivity, it should not be used as a screening tool for PE.

Authors

This post was written by Hector Guerrero, MS4 at UCSD. It was reviewed by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Weekes AJ, e. (2017). Diagnostic Accuracy of Right Ventricular Dysfunction Markers in Normotensive Emergency Department Patients With Acute Pulmonary Embolism. - PubMed - NCBI. Ncbi.nlm.nih.gov. Retrieved 25 September 2017, from https://www.ncbi.nlm.nih.gov/pubmed/26973178
    2. Shopp, J., Stewart, L., Emmett, T., & Kline, J. (2015). Findings From 12-lead Electrocardiography That Predict Circulatory Shock From Pulmonary Embolism: Systematic Review and Meta-analysis. Academic Emergency Medicine, 22(10), 1127-1137. doi:10.1111/acem.12769
    3. Dudzinski DM, e. (2017). Assessment of Right Ventricular Strain by Computed Tomography Versus Echocardiography in Acute Pulmonary Embolism. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 25 September 2017, from https://www.ncbi.nlm.nih.gov/pubmed/27664798
    4. Dresden S, e. (2017). Right ventricular dilatation on bedside echocardiography performed by emergency physicians aids in the diagnosis of pulmonary embolism. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 25 September 2017, from https://www.ncbi.nlm.nih.gov/pubmed/24075286
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Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions

Background

Point-of-care ultrasound (POCUS) has quickly become a core adjunct used in the emergency department (ED) during cardiopulmonary resuscitation (CPR). Specifically, it is now frequently used to evaluate for reversible causes of cardiac arrest (i.e. cardiac tamponade, pulmonary embolism), guide resuscitation, and prognosticate on patient outcomes based on presenting cardiac activity [1]. However at this time, the benefits of the use of POCUS during CPR are not yet clear in terms of patient centered outcomes. What is known to have an effect on patient outcomes is providing high quality CPR, with minimal interruptions, and early defibrillation [2]. POCUS during CPR is often performed during pulse checks and it can take ample time to obtain sufficient views for proper interpretation. One concern is that this can result in unnecessary delays in resuming chest compressions during CPR, leading to harmful effects on patient outcomes.

Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions

 

Clinical Question

Does use of point-of-care ultrasound (POCUS) in cardiopulmonary resuscitation lengthen the duration of pulse checks beyond the guideline recommendation of 10 seconds?

Methods & Study Design

  • Design
    • Prospective cohort study
  • Population
    • This was a single center study performed at an adult, urban, tertiary care, academic medical center
    • All patients, 18 years of age or older, who presented to the emergency department (ED) in cardiac arrest or in whom cardiac arrest occurred while in the ED were eligible for enrollment
  • Exclusion criteria 
    • No documentation of a pulse check
    • Not placed in one of three designated resuscitation rooms with continuous video monitoring capability
    • Video monitoring obtained was not available or image quality was too poor for extraction of data
  • Intervention
    • All cardiac arrest resuscitations were recorded by video camera
      • Researchers recorded the duration of pulse checks (in milliseconds) and whether POCUS was used
  • Outcomes
    • Duration of pulse checks with the use of POCUS

Results

    • 23 patients enrolled
    • 123 individual rhythm checks
    • The use of POCUS significantly increased the pulse-check duration by 8.4 seconds (95% CI, 6.7-10.0 [p<0.0001])
    • Age and BMI did not affect the duration of pulse checks or CPR interruptions
    • No findings on any of the POCUS images prompted a procedure
    • Survival to ED discharge/hospital admission: 35% (8/23)
    • Survival to hospital discharge: 4% (1/23)
    • Survival at 30 days: 4% (1/23)

Strengths & Limitations

  • Strengths
    • Data collected directly from video which removes any bias on recall of events that occurred during cardiopulmonary resuscitation
  • Limitations
    • Small number of patients included in the study
    • Single center study reduces its external validity
    • No information of level of training of US operators
    • No commentary on the impact of POCUS on mortality or neurologic outcomes

Author's Conclusions

"The use of POCUS during cardiac arrest resuscitation was associated with an increase in the duration of pulse checks by 8.4 seconds, causing interruptions in high-quality chest compressions nearly double the 10-second duration recommended by current international cardiopulmonary resuscitation guidelines. It is critical for acute care providers to pay close attention to the duration of CPR interruptions when using POCUS during cardiac arrest resuscitation."

Our Conclusions

With the introduction of novel indications for POCUS, we need to be aware of both the benefits and harms. This is an important study that identifies a potential harm of POCUS during CPR. There is no doubt from this data that POCUS did result in prolonged pulse checks above the guideline recommended 10 seconds. While this study does not directly tell us that POCUS increases mortality in cardiac arrest (as it is much too small), there is clear evidence that increased interruptions in chest compressions during CPR leads to worse outcomes.

The utility of this study is that it identifies a problem with POCUS in which there are clear solutions. With this new evidence, we must take a thoughtful approach to use of POCUS during CPR. Some proposed solutions to address this problem include:

    • Identifying personnel during CPR who can verbalize the time spent during pulse check to make providers acutely aware of when CPR should be resumed ("10, 9, 8, 7...")
    • Recording a POCUS clip for 5 seconds, then reviewing the stored images while CPR is resumed
    • Having a care provider ready to perform POCUS exam with probe on chest just before chest compressions are withheld
    • Use of transesophageal (TEE) POCUS which allows for image acquisition during ongoing CPR

The findings of this paper are definitely not the end of POCUS in CPR, as I find that there are numerous reasons that it is useful (i.e. monitoring of proper chest compression location, identification of reversible etiology of cardiac arrest, prognostication, closure for health care providers during end of resuscitations...), however I would like to see larger studies on this topic as well as quality improvement and awareness of this potential harm of prolonged pulse checks secondary to POCUS utilization.

The Bottom Line

The use of POCUS during CPR may increase the duration of pulse checks beyond the recommended 10 seconds. Care providers should be aware of this potential harm and measures should be taken to prevent unnecessary delays in chest compressions.

Authors

This post was written by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Gaspari R, e. (2017). Emergency department point-of-care ultrasound in out-of-hospital and in-ED cardiac arrest. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 8 September 2017, from https://www.ncbi.nlm.nih.gov/pubmed/27693280

    2. Link MS et al. Part 7: Adult Advanced Cardiovascular Life Support: 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2015 Nov 3;132(18 Suppl 2):S444-64.

    3. Huis In 't Veld MA, e. (2017). Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 8 September 2017, from https://www.ncbi.nlm.nih.gov/pubmed/28754527
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Feasibility and accuracy of bedside transthoracic echocardiography in diagnosis of acute proximal aortic dissection

Background

Acute aortic dissection is a life threatening condition that requires prompt diagnosis and definitive management; dissection involving the ascending aorta is undoubtably an indication for emergent surgical intervention. Previous data suggests that the mortality of type A dissection increases by 1-2% for every hour that passes which further highlights the importance of rapid diagnosis [1-2]. Currently, CT is considered the gold standard that enables the visualization of the entire aorta and can distinguish among the different types of acute aortic syndromes; however this is not always available, requires transferring patients to the CT scanner, and can ultimately generate a significant delay in treatment. Ultrasound is an easily available alternative imaging adjunct that may prove useful in rapid diagnosis of acute aortic dissection, specifically, type A dissection that require emergency surgical intervention.

Feasibility and Accuracy of Bedside Transthoracic Echocardiography in Diagnosis of Acute Proximal Aortic Dissection

 

Clinical Question

What is the accuracy of transthoracic echocardiography (TTE) in the diagnosis of acute type A aortic dissection in comparison to CT (with reference to the intra-operative diagnosis)?

Methods & Study Design

  • Design
    • Retrospective chart review
  • Population
    • This was a single center study involving patients  transferred due to suspected acute type A aortic dissection
    • Cardiac surgery for type A dissection was conducted in 172/178 patients (1 patient refused the operation and died, 5 patients underwent cardiac arrest and died prior to transfer to the operating room)
      • Because intra-operative findings were considered the gold standard reference for the presence of aortic dissection, the 6 patients who died without cardiac surgery were excluded from the final analysis
    • Inclusion criteria:
      • Referral for an urgent surgery due to proximal aortic dissection (Stanford classification Type A)
      • Available results of both CT and bedside TTE
    • Excluded
      • Patients who died prior to cardiac surgery
      • 1 patient who refused surgery
      • Patients who underwent surgical repair of acute type A aortic dissection based on TTE without confirmatory CT
  • Intervention
    • TTE was performed in the emergency department by an “experienced echocardiographer" to evaluate for: maximum ascending aorta diameter, presence of a dissection flap in the ascending aorta, left ventricular ejection fraction, pericardial effusion (and cardiac tamponade), aortic valve morphology and severity of aortic regurgitation
      • Echocardiographic findings were compared to CT findings and intra-operative findings were used as a gold standard
  • Outcomes
    • Identification of type A aortic dissection by TTE
    • Correlation of TTE measurements of maximum ascending aortic diameter with CT and intra-operative findings

Results

    • Statistical analysis with chi square test did not show any statistically significant differences between CT and TTE in the detection of proximal aortic dissection.
    • Additionally, echo revealed concomitant abnormalities (i.e. bicuspid aortic valve, AV calcifications, moderate/severe aortic incompetence, cardiac tamponade), which were all confirmed intra-operatively and influenced the treatment strategy (graft vs. valve-sparing surgery).
    • In patients with any aortic valve abnormalities (bicuspid aortic valve, AV calcifications, significant aortic regurgitation) procedure of choice was replacement by a composite graft (77.59% vs. 49.12%), whereas patients with normal aortic valves were significantly more likely to have the valve sparing surgery (50.88% vs. 22.41%)
    • There was a strong positive correlation between maximum diameter of the ascending aorta measured by TTE and CT (correlation coefficient 0.869)

Strengths & Limitations

  • Strengths
    • This was a feasibility study, and they used a population with known acute type A aortic dissection to determine if TTE could be used to provide both a rapid and reliable diagnosis in proximal aortic dissection
    • Gold standard was intra-operative findings
  • Limitations
    • Retrospective analysis, meaning that the diagnosis of aortic dissection has either already been made or was strongly suspected prior to initiating scanning; some may argue this may falsely increase the noted sensitivity/specificity of TTE
    • All patients who underwent cardiac surgery for acute proximal dissection based on TTE without CT verification (~30% patients at their institution) were excluded from the analysis
    • The TTE was performed by personnel trained in advanced echocardiography which may lower the sensitivity/specificity of these findings in the hands of less experienced operators

Author's Conclusions

"Our data confirm that TTE is a reliable method for diagnosis of proximal aortic dissection. TTE provides a reliable value of maximum diameter of the ascending aorta in comparison to both CT and direct intra-operative measurement. Moreover, TTE gives the additional information that influences the operative technique of choice and identifies the high-risk patients (cardiac tamponade, severe aortic dilatation, severe aortic regurgitation). Our retrospective analysis confirms the pivotal role of TTE in the evaluation of the patients with suspected proximal aortic dissection in emergency room setting."

Our Conclusions

Our conclusions are very similar to author findings on this paper. From the emergency department standpoint, we need the ability to distinguish sick patients from not sick patients and TTE in suspected acute aortic dissection does just that. Looking at this data, TTE measurements of maximum ascending aorta diameter correlate very well with intra-operative measurements. Furthermore, TTE is very accurate at identifying complications of type A aortic dissection such as decompensated heart failure (due to acute aortic regurgitation) and cardiac tamponade, both of which will alter surgical management.

What this means is that if you suspect aortic dissection, a bedside echo should be performed immediately looking for ascending aorta enlargement, dissection flap, and/or complications of dissection. If found, cardiac surgery can confidently be consulted and the patient can either be pushed to the operating room if unstable or pushed directly to the CT scanner by the emergency medicine provider. What this does not mean is that your work up stops here if no findings of dissection are found. If you are truly concerned about aortic dissection then the next step is to proceed with CT for definitive rule out. For more information on evaluation of acute aortic dissection, please read our recent case here.

The Bottom Line

The use of TTE in suspected proximal aortic dissection facilitates a rapid and reliable diagnosis, and shortens the delay to definitive treatment in a subset of high-risk patients.

Authors

This post was written by Ryan Shine, MS-4 at UCSD. It was edited by Michael Macias, MD.

References

    1. HIRST AE Jr, e. (2017). Dissecting aneurysm of the aorta: a review of 505 cases. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 26 August 2017, from https://www.ncbi.nlm.nih.gov/pubmed/13577293

    2. Hagan PG, e. (2017). The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 26 August 2017, from https://www.ncbi.nlm.nih.gov/pubmed/10685714

    3. Sobczyk, D., & Nycz, K. (2015). Feasibility and accuracy of bedside transthoracic echocardiography in diagnosis of acute proximal aortic dissection. Cardiovascular Ultrasound, 13(1). doi:10.1186/s12947-015-0008-5
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Diagnosing Acute Heart Failure in the Emergency Department: A Systematic Review and Meta-analysis

Background

The chief complaint of “dyspnea” represents a very large cohort of patient who present to the emergency department. While acute heart failure (AHF) is a very common diagnosis in the setting of dyspnea, the diagnosis remains challenging when the emergency physician is presented with the undifferentiated dyspneic patient. Interestingly, emergency physicians have varied approaches to the work up and diagnosis of these patients and it is not clear as to which diagnostic element is most crucial in confirming the diagnosis of AHF. Spoiler: Ultrasound proves to be quite useful.

Diagnosing Acute Heart Failure in the Emergency Department: A Systematic Review and Meta-analysis‌

 

Clinical Question

What are the operating characteristics of the diagnostic elements available to the emergency physician for diagnosing acute heart failure?

Methods & Study Design

  • Design
    • This is a systematic review evaluating index test operating characteristics in diagnosing AHF. A medical literature search was performed using PubMed and EMBASE, evaluating peer-reviewed published papers from 1965 through 2015
    • Individual systematic reviews for each index test were conducted by two separate physicians and thereafter reconciled to obtain a comprehensive set of studies on the topic. These were then screened against the inclusion/exclusion criteria for final inclusion into the meta-analysis
    • The reference standard used was a final diagnosis of AHF based on review of clinical data by independent reviewers who were blinded to the study’s primary index test
  • Population
    • All studies included involved patients presenting to the emergency department (ED) with the chief complaint of “dyspnea.”
  • Outcomes
    • Pooled sensitivities, specificities and likelihood ratios (LRs) of index tests for diagnosing acute heart failure in patients presenting to the ED with dyspnea
    • They specifically looked at the following index tests in evaluation of AHF: history and physical exam, ECG, chest x-ray, BNP and NT-ProBNP, lung ultrasound (US), and bedside echocardiography
  • Excluded
    • Patients presenting to urgent care with dyspnea
    • Patients with chronic, compensated heart failure
    • Studies focusing on prognosis or therapeutics and not the diagnosis of AHF
    • Studies with ultrasound images that were not obtained and interpreted by emergency physicians

Results

    • History and Physical: S3 most specific finding for AHF (+LR 4)
    • ECG: Found to be insensitive and unspecific for diagnosing or ruling out AHF
    • CXR: Pulmonary edema was the most specific finding (LR + 4.8). All other imaging findings were insensitive for ruling out heart failure
    • BNP and NT-Pro-BNP: Quite sensitive for ruling out AHF at a threshold of 100/300pg/dL
    • Lung Ultrasound:
      • Presence of >3 B-lines in >2 lung fields is very specific for the presence of AHF
      • Lack of this also sensitive for ruling out acute heart failure
      • High inter-rater reliability
    • Bedside Echo
      • ED provider evaluation of systolic function had high inter-rater reliability with the ultimate ejection fraction assessed by cardiologists on formal echo
      • Restricted Mitral Inflow very specific for ruling in diastolic AHF in patients with preserved systolic function

Strengths & Limitations

  • Strengths
    • Very thorough analysis of the operating characteristics of a plethora of diagnostic elements and sub-elements available to the emergency physician in diagnosing AHF
    • Authors didn’t exclude comorbidities, etiology of AHF or if there was an underlying arrhythmia which increased the generalizability of their results
    • All data was screened and evaluated by two separate physicians
  • Limitations
    • The reference standard was a final diagnosis of AHF made by physicians in retrospective fashion which weakens this as a “gold standard.”
    • The authors did not specifically evaluate or reconcile whether the heart failure was left or right sided
    • Each of the tests or test characteristics were assessed in isolation to determine the likelihood of heart failure. The likelihood of AHF when considering multiple index tests was not assessed
    • As in all large meta-analyses, some spectrum bias may exist as inclusion/exclusion criteria varied among included studies. However, ome of this heterogeneity is likely countered by the pooled analysis and is unlikely to drastically change the calculated LRs

Author's Conclusions

"Bedside lung US and echocardiography appear to the most useful tests for affirming the presence of AHF while natriuretic peptides are valuable in excluding the diagnosis."

Our Conclusions

This is one of the most thorough studies available to assess the likelihood that a patient presenting to the emergency department has acute heart failure based on an index test. There are many old standby diagnostic modalities available to emergency physicians including the history, physical exam, and chest x-ray. Unfortunately, these diagnostic elements are relatively non-specific in establishing that a patient’s acute symptoms are likely or unlikely due to heart failure. BNP and NT Pro BNP are quite useful in ruling out heart failure however these tests take time to result. Ultrasound is rapidly becoming a fundamental tool in every emergency physicians tool belt and should be utilized alongside the primary patient assessment in determining the likelihood that a patient has heart failure. The presence or absence of B lines (>3 in at least 2 fields) is quite specific for ruling in heart failure and the absence is nearly as sensitive as a normal BNP or NT Pro BNP, too. And in the event of systolic heart failure, echo is a great modality to rapidly assess a patient’s pump function; our interpretation is consistent with the formal result obtained by cardiologists [2].

Caution must nevertheless be maintained when evaluating these results. The LRs found in these studies were calculated independently of other findings and in reality, the emergency physician takes multiple factors from the history, physical exam, and other diagnostic modalities, to ultimately come to a definitive diagnosis. Essentially, the short answer is that no single test should be taken as definitive in diagnosis of AHF (or any diagnosis for that matter) and the emergency physician should follow a bayesian approach using pre- and post- test probabilities from their fund of knowledge to rule in and rule out cannot miss diagnoses. Lastly, with regards to this study, physicians should be wary about interpreting these results in the context of renal failure primarily but also superimposed pneumonia or underlying concern for pulmonary embolism as these patients were excluded in a number of papers included in this meta-analysis.

The Bottom Line

Bedside ultrasound to evaluate for the presence or absence of pulmonary edema should be an integral part of the emergency physicians approach to evaluating patients to the emergency department with undifferentiated dyspnea.

Authors

This post was written by Matt Correia, MD PGY-2 at UCSD. It was edited by Michael Macias, MD.

References

    1. Martindale JL, e. (2017). Diagnosing Acute Heart Failure in the Emergency Department: A Systematic Review and Meta-analysis. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 14 August 2017, from https://www.ncbi.nlm.nih.gov/pubmed/26910112
    2. Moore CL, e. (2017). Determination of left ventricular function by emergency physician echocardiography of hypotensive patients. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 14 August 2017, from https://www.ncbi.nlm.nih.gov/pubmed/11874773
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Comparison of Four Views to Single-View Ultrasound Protocols to Identify Clinically Significant Pneumothorax

Background

Ultrasound has become a key adjunct for the initial evaluation of trauma patients in the emergency department (ED), with the eFAST, or extended focused assessment with sonography in trauma examination, including lung evaluation for the presence of a pneumothorax (PTX) or hemothorax. While prior research has shown ultrasound (US) to be very effective at identifying a PTX [1], there is no standardized imaging protocol that has been shown be superior to others. The two most common approaches are a single view of each hemithorax and four views of each hemithorax [2] —this paper sets out to determine if the single view strategy is sufficient to identify a clinically significant PTX.

Comparison of Four Views to Single-view Ultrasound Protocols to Identify Clinically Significant Pneumothorax

 

Clinical Question

Does the single-view or four-view lung US technique have a higher diagnostic accuracy for the identification of clinically significant PTX in trauma patients?

Methods & Study Design

  • Population
    • The study was conducted at a single urban academic ED with an annual volume of 130,000 patients and a dedicated Level I trauma service staffed by trauma surgeons and EM physicians. Adult patients with acute traumatic injury who were undergoing a CT scan of the chest as part of their clinical care were eligible for enrollment.
  • Intervention
    • Patients were assigned to one of two imaging protocols, a single view of each hemithorax or four views of each hemithorax prior to any CT imaging being done, with US images obtained by emergency physicians or the attending trauma surgeon using a 7.5-Mhz (5- to 10-MHz) linear array transducer. US exams were performed by both residents and attending physicians who had been credentialed in both US protocols.
  • Outcomes
    • Researchers looked for the ability of US to identify clinically significant PTX requiring chest tube placement; a PTX was considered clinically insignificant if the radiologist, who was blinded to the US interpretation, read the CT scan as a thin collection of air up to 1 cm thick in the greatest slice or seen on fewer than five contiguous slices.
  • Design
    • This was a randomized, prospective trial on trauma patients.
  • Excluded
    • The study excluded any patient who was too unstable and required clinical care that prevented performing a chest wall US, patients with a chest tube in place prior to arrival, children, pregnant women, and prisoners.

Results

    • For clinically significant PTX, CXR showed a sensitivity of 48.0% and specificity of 100%, a single view US showed a sensitivity of 93.0% and a specificity of 99.2%, and four views showed a sensitivity of 93.3% and specificity of 98.0%. There was no statistically significant difference in either sensitivity or specificity when comparing single view and four-view for clinically significant or any PTX.

Strengths & Limitations

  • Strengths
    • Randomized, prospective trial
    • 100% agreement between the initial US read by the performing provider and the study author, for a Cohen’s kappa of 1
  • Limitations
    • Study was conducted at a single center with a limited number of US operators
    • Standard prehospital approach to spinal immobilization that results in placement of patients supine on a long board - in areas where this approach may differ (e.g., patients arrive semirecumbent or upright), the positioning of a PTX in the chest may be altered, rendering a single view of the anterior chest wall less accurate
    • As this study was a convenience sample that required the treating physician to remember to enroll the patient and randomize them prior to performing the US, there is a possibility of selection bias

Author's Conclusions

"The sensitivities are equivalent for both a single view and four views of each hemithorax when using point-of-care ultrasound to evaluate for a clinically significant pneumothorax in the trauma population.  The additional time required for additional views should be weighed against the lack of additional diagnostic accuracy when evaluating critically ill and time-sensitive trauma patients in the ED."

Our Conclusions

Although not all PTXs are located anteriorly and multiple views of each hemithorax may be thought to maximize sensitivity and/or allow the physician to be able to attempt to quantify the size of the PTX, performing eight views instead of two views during the eFAST requires extra time while adding no diagnostic value.  From this study, it appears that a single view on each side of the thorax is sufficient to detect clinically significant PTXs on trauma patients.

As with any diagnostic tool, it is important to remember its limitations. Specifically, the US exams in this study were done in supine patients, who were brought in by EMS in a supine position, allowing the pneumothorax to move to the most anterior portion of the chest. Caution should be taken when applying the test characteristics of this study to patients that are not in the supine position. There was also one patient who had a significant PTX that was missed by US and required a chest tube. This patient had received a needle decompression by prehospital providers and was randomized to a single anterior US chest view that was performed just lateral to the needle insertion site which may have led to false negative US exam. It appears this specific group of patients may benefit from a more comprehensive four-view lung examination.

 

The Bottom Line

A single anterior view on each side of the chest in a supine patient is sufficient to detect clinically significant pneumothoraces.

Authors

This post was written by Ben Foorman, MS4 at UCSF. It was edited by Michael Macias, MD.

References

    1. Lichtenstein DA, e. (2017). Ultrasound diagnosis of occult pneumothorax. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 28 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/15942336
    2. Blaivas M, e. (2017). A prospective comparison of supine chest radiography and bedside ultrasound for the diagnosis of traumatic pneumothorax. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 28 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/16141018
    3. Helland G, e. (2017). Comparison of Four Views to Single-view Ultrasound Protocols to Identify Clinically Significant Pneumothorax. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 28 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/27428394
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