Ultrasound – Emergency Medicine Literature of Note

The FAST Is Wrong, Bob

What happens when you routinely do an unnecessary test that rarely changes management? Essentially, nothing.

So, here is a randomized, controlled trial demonstrating precisely that.

This trial looks at the Focused Assessment with Sonography in Trauma exam, as performed in pediatric blunt trauma patients. The FAST, if you recall, is generally indicated primarily for hypotensive blunt trauma patients – that is, it has supplanted diagnostic peritoneal lavage as a non-invasive alternative. It does not routinely provide a diagnosis, but it helps guide initial management and may triage a patient to emergency laparotomy rather than resuscitation and further testing. Therefore, in a stable pediatric trauma patient, the pretest likelihood of a significant finding – free fluid relating to hemorrhage from trauma – is quite low. Furthermore, because many significant intra-abdominal injuries to solid and hollow organs are missed by ultrasound, a negative FAST has poor negative likelihood ratios and should not substantial affect decisions for advanced imaging as otherwise clinically indicated.

So, then, this trial is a bit of an odd duck with respect to any expected difference observed – and that’s precisely what they found in their “coprimary outcomes”. Among the 925 patients randomized to trauma team assessment alone or trauma team assessment supplemented by Emergency Physician FAST, there was no significant difference in imaging, Emergency Department length of stay, missed intra-abdominal injuries, or total hospital charges. The authors hypothesized, based on adult data, there might be savings at least in ED LOS – though, I might rather suggest adding in one more non-diagnostic test to the acute evaluation is more likely to mildly prolong LOS.

There are also issues generalizing this study setting, where ~53% of patients in each cohort received CTs, to other institutions. Interestingly, mean time to CT was over 2 1/2 hours, suggesting a great deal of observation and reassessment drove imaging decisions rather than the initial evaluation. Then, after expert review, EPs incorrectly identified a positive FAST in 10 out of 23 cases – and missed 11 true positives, as well. The FAST, even at this academic medical center where it is done as routine, cannot be relied upon.

The sum of this evidence is: no change in practice. A stable patient is, by definition, stable for imaging as indicated – and the FAST is an unnecessary part of the initial clinical evaluation.

“Effect of Abdominal Ultrasound on Clinical Care, Outcomes, and Resource Use Among Children With Blunt Torso Trauma”

http://jamanetwork.com/journals/jama/article-abstract/2631528

Ultrasound to Confirm Central Line Placement

Yes, it can be done – probably.

This is a meta-analysis and systematic review of 15 studies comparing ultrasound to conventional chest radiography to confirm central line placement – and to determine any malposition. There is good news: ultrasound reliably detected the few reported pneumothoracies, and was nearly 100% specific for catheter malposition. However, there is also bad news: sensitivites for catheter malposition were all over the map, and the quality of the included studies was universally poor and prone to systemic bias.

It does seem to be a little self-fulfilling to use an ultrasound to place a catheter – and then to turn around use your skills to verify placement. After all, the operator placing the catheter is highly vested in the catheter placement being correct. That said, some of these data are likely valid – an experienced operator can probably use anå ultrasound to verify the location in the correct vessel when a catheter tip is noted on high-quality visualization of either the correct or an aberrant location. Chest x-ray is hardly a foolproof gold standard – and there may be clinically important ramifications to the delays in obtaining chest radiography. Due to the wide ranges of sensitivity, however, any effort to routinely utilize ultrasound for this purpose should be carefully followed by a quality assurance program.

“Diagnostic Accuracy of Central Venous Catheter Confirmation by Bedside Ultrasound Versus Chest Radiography in Critically Ill Patients: A Systematic Review and Meta-Analysis”

https://www.ncbi.nlm.nih.gov/pubmed/27922877

The Value-Add of Ultrasound to STONE Score

There are a few major questions to be addressed in patients with suspected renal colic:

Is there an infection?
If there is a stone, will it pass spontaneously or require urologic intervention?
If I make a clinical diagnosis without CT, will I miss an important alternative diagnosis mimicking stone?

The STONE score addresses the last question – using a weighted decision instrument to classify patients with suspected stone into low-, moderate-, and high-risk cohorts for ureteral stone disease. There are some issues with face validity for STONE, and likewise the validation has shown its performance to be somewhat inexact. However, it helps reinforce gestalt and aids in shared decision-making.

This study adds in point-of-care ultrasound to assess the degree of hydronephrosis. The hope of these authors was the presence of hydronephrosis would improve the performance of the STONE score by identifying the few patients with stones at the low- and moderate- end, while also using moderate or greater hydronephrosis to predict the need for subsequent urologic intervention.

The answer: only marginally.

Generally, the most useful positive likelihood ratios are above 10, and the most useful negative likelihood ratios are below 0.1. In this study, only one LR potentially met that criteria. The presence of moderate or greater hydronephrosis in a patient with a low likelihood of stone disease had a +LR of ~20 for both the presence of stone and for stone disease requiring urologic intervention – but this +LR was based on only a handful of patients, and the 95% CIs range from 4 to 110.

Lastly, did the presence of hydronephrosis rule out any important alternative diagnoses? No. Out of 835 patients, there were 54 with an important alternative diagnosis. There were 11 patients with hydronephrosis plus an important alternative, including 3 appendicitis, 1 cholecystitis, 2 diverticulitis. The presence of moderate or severe hydronephrosis was helpful, but would not obviate imaging for an alternative diagnosis if indicated.

“STONE PLUS: Evaluation of Emergency Department Patients With Suspected Renal Colic, Using a Clinical Prediction Tool Combined With Point-of-Care Limited Ultrasonography”
http://www.ncbi.nlm.nih.gov/pubmed/26747219

The No-CT in Trauma Experience

In many trauma centers, the Emergency Department role is essentially: place an IV for which contrast may be delivered for CT. Oh, yes, there’s some airway management, perhaps a FAST exam, some rolling and cutting of clothing, and the remainder of our expertise should not be diminished, but modern management has been distilled to: trauma = pan-scan.

Except in San Diego.

This fascinating paper describes 11 years of experience at a Level 1 trauma center in which the vast minority of their patients underwent automatic CT. Between the hours of 8AM and 11PM, a resident and staff ultrasonographer were available for ultrasound examination of trauma patients. At the discretion of the attending surgeon, the ultrasonographers performed an examination consisting of seven abdominal windows, bilateral visceral organ windows, and cardiac windows.

And, of the 19,126 trauma patients included in this study, essentially all patients presenting between 8AM and 11PM underwent this ultrasound. Minus the 13 patients who went directly to the OR, this constitutes 12,565 patients initially screened with ultrasound. Of these, 12,070 were judged to be negative examinations. By the authors definition of false negative, a positive exploratory laparotomy finding, only 35 ultimately required such – a false negative rate of 0.29%. Comparatively, CT was performed off-hours in 6,548 patients, and had a 0.1% false negative rate.

There were, of course, a mix of patients with positive ultrasound results who ultimately had negative CTs, and 1,119 negative ultrasounds who underwent CT with a 86 positive results. So, there’s a lot of details and hidden corners to evaluate and analyze beyond their narrow definition. But, still, impressively, their trauma protocol at a Level 1 center managed to spare half the patients the ubiquitous pan-scan.

Fascinating!

“Complete ultrasonography of trauma in screening blunt abdominal trauma patients is equivalent to computed tomographic scanning while reducing radiation exposure and cost”
http://www.ncbi.nlm.nih.gov/pubmed/26218686

EM Physicians Can Accurately Measure Systolic Function… Well Not Really

A guest post by Dr. Andrew Kirkpatrick (@AskEMdoc), an Emergency Medicine resident at the University of Texas Medical School at Houston.

With all of the recent advancement in the field of Emergency Department (ED) ultrasound, you may be tempted to think Emergency Physicians are masters of the bedside cardiac ultrasound and the assessment of systolic heart failure. Despite the misleading title, the results of this article would suggest that is not the case.

This is a prospective observational study to determine if E-point Septal Separation (EPSS) measurements made by emergency physicians correlated with calculated Left Ventricular Ejection Fraction (LVEF) measured by cardiologist using comprehensive Trans-Thoracic Echocardiography (TTE). Cardiac ultrasound and TTE were performed on 80 patients between the ages of 22 and 100 years old, of which 71 were included in the final analysis. The study took place in the academic setting of Denver Health, conducted by 3 ultrasound fellows who had done at least 100 ultrasound scans. They were given a 10 minute didactic presentation and supervised doing 3 EPSS measurements before they were set loose in the hospital to find patients who had undergone TTE in the last 24 hours.

Based on their results, the authors conclude that an EPSS of greater than 7mm is ideal for diagnosing severely reduced LVEF (<30%), with a sensitivity of 100% and a specificity of 51%. This suggests EPSS is only useful in ruling out severe systolic heart failure – as values over 7mm were poor predictors of actual LVEF. This inability to provide predictive information is well demonstrated by Figure 2, in which there are 3 patients with EPSS clearly in the range associated with severe systolic dysfunction- 20-22mm – and 2 of these 3 had normal ejection fraction on formal echocardiography. Put another way, only 31 of the 63 patents with EPSS >7mm had moderate heart failure, calling into question the author’s suggestion the EPSS is a tool to accurately assess for LVEF. In addition to the previous findings, the authors find that an EPSS of >8mm is a poor predictor of any systolic dysfunction with a sensitivity and specificity of 83.3% and 50.0%, respectively. The authors also assessed the ability of emergency physicians to visually estimate ejection fraction, and found generally poor correlation with echocardiography and only fair interobserver reliability.

There are several problems with this paper. The sample size was small, and generalizability to Emergency Department patients may be limited because a majority of the population studied was inpatient. More importantly, three ED ultrasound fellows performed all of the EPSS measurements. These physicians having a special interest in ultrasound are likely more adept at wielding an ultrasound than the average emergency physician. At best, this article makes a weak case for the clinical relevance of EPSS. And, ultimately, subtle systolic dysfunction that may or may not be picked up by using a cutoff EPSS of >8 may not be as important as the ejection fraction that is so low it can be seen on the ultrasound screen from across the room.

“E-point septal separation: a bedside tool for emergency physician assessment of left ventricular ejection fraction”

http://dx.doi.org/10.1016/j.ajem.2014.02.014

Farewell, CT Stone Protocol

Ureterolthiasis has become a poster child for over-utilization of advanced imaging. Despite the relative level of distress kidney stones cause our patients, the use of computed tomography has never been associated with improved outcomes – yet, CT is widespread for its diagnostic utility, contributing substantially to $2 billion in annual healthcare expenditures for this condition in the U.S. alone.

This, however, is a comparative effectiveness evaluation promoting ultrasound for the diagnosis of ureterolithiasis in the Emergency Department, a three-pronged evaluation comparing CT, formal ultrasonography by radiology technicians, and bedside Emergency Department ultrasonography. Essentially, the objective of this study was to compare safety – regarding, in a sense, whether the additional information supplied by CT was valuable for the detection of life-threatening alternative diagnoses. And, with respect to this outcome all strategies had, essentially, the same number of “misses” during the follow-up period – mostly acute cholecystitis, one case of appendicitis, and a smattering of other thoracoabdominal diagnoses. And so – ultrasonography, even our amateur sort in the ED, is “just as good”.

Of course, there are a few oddities associated with this publication. There are, bizarrely, three “primary outcomes”, and the authors explicitly choose to report only two of them. Total costs of care was intended to be an outcome, but the authors simply state those results will not be reported in this paper. This study also has an interestingly low incidence of ~33% confirmed ureterolithiasis – which may result from their lack of a “gold standard” for diagnosis of stone, relying on patient-reported stone passage or follow-up for stone removal. Or, it could be enrollment of a population with an oddly low incidence of hematuria – only ~63% of enrolled patients exhibited this common finding with a sensitivity of >80%. I’d be curious to see the incidence of hematuria in the cases with alternative diagnoses, although there would likely be too few to draw any substantial conclusions.

There was also substantial crossover from the ultrasonography cohorts. 40.7% of those randomized to ED ultrasonography and 27.0% randomized to radiology ultrasonography ultimately underwent CT. And, this crossover reveals the limitation of ED ultrasonography: a “sensitivity” of 54%, compared with a “sensitivity” of 88% for CT (the unreliable gold standard for diagnosis limits test characteristic calculations). There was also a major exclusion relevant to the U.S. population: women over 250 lbs and men over 285 lbs. Unfortunately, a substantial portion of the U.S. exceeds such superlative mass – and the generalizability of these results to that population is open to reasonable variability.

The take home point, however, is a little less reliable. Yes, if you select patients for imaging similarly to these authors and visualize unilateral hydronephrosis in the setting of suspected ureterolithiasis, it is fair to terminate your diagnostic pathway. However, the primary fallacy of this study design is predicated on the debatable necessity of performing imaging for all suspected ureterolithiasis. One can make a very reasonable argument ureterolithiasis can be adequately diagnosed on clinical grounds, and advanced imaging is required only in the minority of cases, regardless of the findings on bedside ultrasound. The vast majority of ureterolithiasis carries a relatively benign prognosis of recurring and remitting pain of a few weeks duration, and return precautions or outpatient follow-up for persistent symptoms is likewise a reasonable course of action.

“Ultrasonography versus Computed Tomography for Suspected Nephrolithiasis”
http://www.nejm.org/doi/full/10.1056/NEJMoa1404446

ED Hocus POCUS … or Just a Hoax?

A guest post by Rory Spiegel (@EMNerd_) who blogs on nihilism and the art of doing nothing at emnerd.com.

A landmark paper recently published in Lancet Respiratory Medicine is certainly destined to send the ED Ultrasound world into a tizzy. This is the first RCT examining the utility of Emergency Department based Point of Care ultrasound (POCUS) for patients presenting with undifferentiated respiratory complaints. Authors randomized patients presenting to the ED with signs or symptoms concerning for a respiratory etiology to either a standard work up as determined by the treating physician or the addition of POCUS performed by a single experienced operator. The US protocol consisted of sonographic examination of the heart, lungs and lower extremity deep veins to identify possible causes of patients’ symptoms. The authors’ primary outcome was the percentage of patients with a correct presumptive diagnosis 4 hours after presentation to the Emergency Department as determined by two physicians blinded to ED POCUS findings, but with access to the records of the entire hospital stay.

Using this POCUS protocol the authors found stunning success in their primary endpoint. Specifically, the rate of correct diagnoses made at 4-hours in the POCUS group was 88% compared to 63.7% in the standard work up group. Furthermore 78% of the patients in the POCUS group received “appropriate” treatment in the Emergency Department compared to 56.7% in the standard work up group.

Though promising, these benefits did not translate into improvements in true patient oriented benefits. Though not statistically significant, the observed in-hospital and 30-day mortality trended towards harm in the POCUS arm ( 8.2% vs 5.1% and 12% vs 7% respectively). Nor was there any meaningful difference in length of stay or hospital-free days between those in the POCUS group and those in the control group. Even more concerning, was the significant increase in downstream testing that occurred in patients randomized to the POCUS group. Specifically the amount of chest CTs (8.2% vs 1.9%), echocardiograms (10.1% vs 3.8%) and diagnostic thoracocenthesis (5.7% vs 0%). This, of course, may be statistical whimsy, but these findings are concerning for a certain degree of overdiagnosis. Unless detected pathology results in improved patient outcomes secondary to treatment, are we truly helping, or just piling on potential costs of increased vigilance?

I’m sure we all have experienced firsthand the utility of bedside US and this is by no means a call to abandon our probes, but rather an acknowledgement of the possibility of subtle harms. We must keep in mind, all testing comes at a price no matter how non-invasive and radiation-free it appears. The cost in this case is information and how we choose to act on it. This would certainly not be the first time increased access to medical technology has lead to such unintended consequences.

“Point-of-Care Ultrasonography in Patients Admitted With Respiratory Symptoms: a Single-Blind, Randomised Controlled Trial”
http://www.ncbi.nlm.nih.gov/pubmed/24998674

It’s Ultrasound Fightin’ Time

Trauma showdown: pneumothorax. Chest x-ray or ultrasound?

The answer on the surface is pretty clear – unless you delve a little deeper into the precise question asked.

This meta-analysis of head-to-head ultrasound vs. CXR studies for the diagnosis of pneumothorax shows what we all essentially expect: the sensitivity of ultrasound is greatly superior, while specificity is statistically similar. Sensitivities for ultrasound were better for trauma, using the linear (high frequency) probe, and when performed by Emergency Physicians, and ranged from 73% to 85%. CXR sensitivities ranged from 32.6% to 49%, with heterogeneity based on study enrollment methods. Specificities for each were ~99%.

What the study does not address – are these pneumothoracies clinically meaningful? Ultrasound certainly finds more disease, but the newly identified disease will all be closer to the benign end of the spectrum. I guarantee there are patients out there with normal CXR in the setting trauma, who then receive an ultrasound positive for pneumothorax, and are then referred to CT scan and surgical evaluation – would have ultimately been fine. Before we move along to detecting more “disease”, we ought to examine the downstream consequences of missing or detecting these small pneumothoracies.

“Pleural ultrasonography versus chest radiography for the diagnosis of pneumothorax: review of the literature and meta-analysis”
ccforum.com/content/17/5/R208‎

Ultrasound First For Pulmonary Embolism?

Akin to the ultrasound first for appendicitis protocol currently in use, the authors of a recently published study in CHEST propose using ultrasound before CTPA in patients where the diagnosis of pulmonary embolism is being considered.

Their protocol consisted of bedside thoracic and lower extremity ultrasounds to identify either a confirmatory DVT or an alternative diagnosis that would account for the patient’s current presentation. In both the ED and inpatient settings, ICU physicians evaluated this protocol’s performance in 100 patients. The 54 patients who were determined, due to an alternative diagnosis found on ultrasound, not to require further testing, none of them were found to have a pulmonary embolism on confirmatory CT. Of the remaining 40 patients (42%) whose ultrasound revealed no convincing alternative diagnosis or lower extremity DVTs, 12 were found to have pulmonary embolisms on their confirmatory CTPA. The authors conclude that though further studies are needed, an ultrasound first strategy will reduce the number of CTs obtained to rule out pulmonary embolism.

Though I am not opposed to the utilization of ultrasound as a bedside tool, using it to rule out pulmonary embolisms is a flawed paradigm. The proposed protocol is not one which rules out PE, it in fact does just the opposite. This protocol takes advantage of the high specificity of ultrasound for the diagnosis of pneumonia, pulmonary edema, and DVT. It employs the strategy of ruling in an alternative diagnosis or a lower extremity DVT. If no convincing diagnosis is discovered the patient will then move on to the more traditional rule out strategy of CTPA. This study essentially uses bedside ultrasound to address the two most heavily weighted criteria on the Well’s Score, “an alternative diagnosis that is less likely than pulmonary embolism” and “signs and symptoms of deep venous thrombosis”. In no way is this protocol fatally flawed. It has the potential to add a great deal to clinical decision making. Unfortunately it does not address the more serious epidemic in the current management of pulmonary embolisms. That is the egregious over-testing and subsequent over-diagnosis of pulmonary embolism in the ultra low risk patient.

“Ultrasound Assessment of Pulmonary Embolism in Patients Receiving Computerized Tomography Pulmonary Angiography”
journal.publications.chestnet.org/article.aspx?articleid=1763837

For more nihilism, emergency medicine and the art of doing nothing see emnerd.com and @CaptainBasilEM

Ultrasound First For Pulmonary Embolism?

“Ultrasound Assessment of Pulmonary Embolism in Patients Receiving Computerized Tomography Pulmonary Angiography”
journal.publications.chestnet.org/article.aspx?articleid=1763837

For more nihilism, emergency medicine and the art of doing nothing see emnerd.com and @CaptainBasilEM