Monday, November 26, 2012

Ultrasound – For Long Bone Fracture

I have to say, I'm a little confused by all the new SonoSite television ads – direct-to-consumer marketing for sports medicine ultrasonography?  Or for zero-complication central line placement?  Weird.

But, I digress.  A little.  This is a pediatric study of lightly trained ultrasonographers with varying levels of expertise using ultrasound to diagnose long-bone fractures.  They performed 98 ultrasound examinations that were followed up by plain radiography, and they picked up 41 of the 43 fractures present, with 8 false positives:  95% sensitivity and 85% specificity.  Six required reduction, all of which were identified as meeting criteria for reduction on ultrasound – as well as one additional false positive from a distal radius fracture.


As a feasibility study, it's a nice little pilot.  As a practice-changing strategy, it needs larger sample sizes and external validity.  However, it does seem as though it will soon become reasonable to use bedside ultrasound to quickly rule-out fracture in patients with a low pre-test probability, while plain radiography will continue to play a role in advanced orthopedics management.


"Emergency Ultrasound in the Detection of Pediatric Long-Bone Fractures"
www.ncbi.nlm.nih.gov/pubmed/23114237

Wednesday, November 21, 2012

All Elevated Troponins Are Not MI

Have you ever received sign-out on a patient, heparinized, awaiting cardiology consultation – and later, at your leisure, realized the troponin level just barely tips into positive territory and probably has nothing to do with acute coronary syndrome?

I know you have.


This is the cardiology "expert consensus" on interpretation of troponin elevations – 25 pages of clinical summary and 360 references worth of dissecting what an elevated troponin really means.  There's an hour-long lecture worth giving based on this publication.


The key portions include:
 - Figure 1, which is a nice conceptual overview in which elevated troponins are separated into their "ACS" and "non-ACS" categories.
 - Section 6, which discusses the possible role (if any) for troponins in non-ischemic conditions.
 - Appendix 4, the clinical conditions in which positive troponins are non-cardiac and confounding in origin.


Positive troponins need to be evaluated properly in their clinical context, and this is a lovely (if very, very long) reference document for describing it.


"ACCF 2012 Expert Consensus Document on Practical Clinical Considerations in the Interpretation of Troponin Elevations"
www.ncbi.nlm.nih.gov/pubmed/23154053

Monday, November 19, 2012

ECASS III Errata

This is my favorite sort of article to feature on this site – a probably-overlooked letter about a certainly-overlooked feature of a landmark trial.

This author, from Mt. Sinai, notes last year, the authors of ECASS III updated their online manuscript to change a p-value in their baseline characteristics from 0.03 to 0.003.  Since these are p-values for baseline characteristics, they're only for illustrative purposes – considering, in randomized controlled trials, all the differences do occur by "chance".  However, the conceptual interpretation of this change in ECASS III is the placebo group was inadvertently randomized to have a history of prior stroke by a 7% absolute difference – and the chance of that occurring randomly has now admitted to be 1 in 300 rather than 1 in 30.  When tremendously unlikely differences in baseline characteristics occur "by chance", it raises troubling questions regarding whether they truly occurred randomly.


Additionally, the author of this letter also makes the astute point that, because this difference in baseline characteristics did not reach statistical significance by the ECASS III authors' definition (0.004), it was not adjusted for in their data analysis.  
In his adjusted reanalysis (data not shown), the significance of outcomes favoring thrombolysis disappears (OR 1.19, CI 0.89-1.59).  Not necessarily surprising, considering the updated meta-analysis including IST-3 data published in The Lancet also makes the statistical significance of the benefit of thrombolysis disappear past 3 hours.

Thrombolysis for acute stroke remains some of the most distorted treatment data in emergency medicine, where this heterogenous patient population is being overtreated based on "eligibility", rather than "likelihood of benefit".

"Implication of ECASS III error on emergency department treatment of ischemic stroke."
http://www.ncbi.nlm.nih.gov/pubmed/23141561

Friday, November 16, 2012

Don't ß-Blockade Cocaine Chest Pain

Or, specifically, ignore this evidence that says you can.

There may be some mythology to the hypothesis that non-selective ß-receptor blockade is contraindicated in the setting of cocaine chest pain.  After all, the supporting evidence consists only of small, laboratory case series – and other outcomes-oriented data suggests ß-blockade is cardioprotective, as we already know.  However, this study is a perfect example of inappropriately extending a conclusion from retrospective data.

These authors identified 378 patients from retrospective chart review, selecting patients with chief complaints of chest pain and positive toxicology tests for cocaine.  Unfortunately, urine toxicology tests for cocaine stay positive for days following the initial episode of cocaine use.  Therefore, there is no way from these chart review methods to reliably differentiate the acuity of the cocaine intoxication.  

This is important because a major flaw in retrospective reviews, such as this, is a confounding selection bias.  If all cocaine chest pain patients are not created equal – the neurohormonal effects of cocaine last on the minutes to hours while their drug tests are positive for days – then providers may be selecting patients for beta blocker use/non-use based on acuity information this review cannot detect.  If providers are excluding patients from beta-blockers based on the acuity of their intoxication – as many sensible providers might – and only using beta-blockers in non-acute presentations, then this study may not include any of the population of interest.

The authors' statement of "We have found that BB use in the acute management of cocaine-associated chest pain did not increase the incidence of MI" cannot be defended as accurate, as it is based on indefensible assumptions.

"Safety of β-blockers in the acute management of cocaine-associated chest pain"
http://www.ncbi.nlm.nih.gov/pubmed/23122421

Wednesday, November 14, 2012

The Hazards of Love

"Sexual activity is mechanically dangerous, potentially infectious and stressful for the cardiovascular system."

Indeed!

According to this retrospective review of 11 years of electronic health records from University Hospital Bern, Switzerland, they identified 445 patients seeking emergency care secondary to sexual intercourse.  The majority of emergency department visits were secondary to suspected infectious etiologies (62%), but neurologic complaints, trauma, and cardiovascular incidents comprised the remaining portion.  

The trauma portion probably speaks for itself without need for additional detail.  There was one myocardial infarction and one aortic dissection.  Among the "various complaints", two patients were diagnosed with "eczema".  However, among the neurologic emergencies, there were 12 cases of subarachnoid hemorrhage and 11 cases of – ah – "transient global amnesia".

All things being equal, at least, sexual activity was only associated with 0.1% of emergency department visits – hardly the most dangerous of potential choices of recreation.

"Sexual activity-related emergency department admissions: eleven years of experience at a Swiss university hospital" 
http://www.ncbi.nlm.nih.gov/pubmed/23100321

Monday, November 12, 2012

Viral Testing in Children With Fever

This study attempts to address the question we've been asking ourselves since the dawn of antibiotics – does this child with a fever have a viral infection, or a bacterial infection?  Of course, in reality, we should be asking a more complicated question – does this child have a viral infection, or a bacterial infection for which the increased likelihood of positive outcome with antibiotics outweighs the harms of the antibiotics?  But, I digress.

One hypothesis that is bandied about in literature and practice is, if rapid viral testing were available in the Emergency Department, perhaps a positive viral test result would reduce the likelihood of antibiotic usage.  These folks from Washington University performed viral PCR for a host of common viruses on 75 children with fever without a source, 15 children with probable bacterial infections, and 115 afebrile children presenting for outpatient surgery.  The authors note the patients with bacterial infections were less likely to test positive for a virus – and suggest prospective trials might describe a strategy in which viral testing decreased antibiotic use.

In their cohort, 55% of children aged 2 to 12 months and 39% of those aged 13 to 24 months with no obvious source for fever received antibiotics.  This is irresponsible lunacy.  However, a much faster, cheaper way to decrease antibiotic use is:  to simply return from the abyss of antibiotic overuse to a land of rational practice.  

After all, 40% of the bacterial infections and 35% of the outpatient surgical patients tested positive for a virus – clearly indicating the presence of a virus has limited association with acute viral illness or absence of an acute bacterial infection.  More tests are not the answer – at least, certainly not this battery of PCR tests.

"Detection of Viruses in Young Children With Fever Without an Apparent Source"
http://www.ncbi.nlm.nih.gov/pubmed/23129086

Friday, November 9, 2012

New Risks For Low-Risk Chest Pain

My newest publication, e-published today in the Emergency Medicine Journal of the British Medical Journal.

Currently requires an institutional subscription.

"CT coronary angiography: new risks for low-risk chest pain"
http://emj.bmj.com/content/early/2012/11/07/emermed-2012-201795.abstract

What To Do With The "Dizzy" Patient?

As the authors in this retrospective review state, "Vertigo/dizziness is a common and challenging problem faced by the ER physician."  And, this is obviously true.  Is it dysequilibrium?  Is it true vertigo?  Is it central or peripheral?  And, finally, "now what"?

This is a clearly pro-MRI and con-CT study which, unfortunately, leads to a massive disconnect with reality.  For most institutions, CT might be feasible, but MRI comes to town once a week for scheduled studies only.  But, in this review of 448 head CTs for dizziness, the CT picked up essentially 10 interesting findings – but 16% of the subset of follow-up MRIs performed changed the initial diagnosis.  Mostly, the missed diagnoses on CT were posterior circulation strokes and intracranial masses.  

So, essentially what they observed was more false negatives than true positives for CT.  This implies – at least in a retrospective fashion – that if your pretest probability is high enough for an intracranial process causing dizziness, the intention ought to be to conclude your investigations only with a negative MRI.  I think most folks – given infinite resources – would agree.  Otherwise, you'll need to base imaging (if any) on clinical findings and risk factors for cerebrovascular disease in an attempt to develop an estimate for their true probability.

"Utility of head CT in the evaluation of vertigo/dizziness in the emergency department"
www.ncbi.nlm.nih.gov/pubmed/22940762


Wednesday, November 7, 2012

Unsurprisingly, NHAMCS Data is Flawed

The National Hospital Ambulatory Medical Care Survey is a massive database of abstracted patient records, systematically generated to produce a representative sample of the nation's Emergency Department visits.

It should come as no surprise that retrospectively abstracted data from the electronic medical record sometimes fails to accurately reflect patient care.  The important question, however, is "how often?"  This review of NHAMCS by one of the Annals editors looked at a measurement that ought to be pretty obvious – intubation.  If you can't figure out whether a patient has been intubated via chart review, there's some serious issues with your data sourcing.  However, in this review of NHAMCS, the author interprets up to one in four charts as being potentially inaccurate due to inconsistencies between documented intubation and the final disposition of the patient (e.g., non-ICU settings, home, observation status, etc.)

Now, there are some instances in which patients are intubated in the Emergency Department – yet not subsequently dispositioned to a critical care or morgue – but these "temporary" intubations certainly do not constitute 25% of intubations.  The author goes on to note that Annals publishes a NHAMCS study at least twice a year – relatively influential towards practice given the Impact Factor – and the flaws in this data should limit the relative weighting of its importance.

"Congruence of Disposition After Emergency Department Intubation in the National Hospital Ambulatory Medical Care Survey"

Monday, November 5, 2012

Sometimes, the Dead (by Ultrasound) Rise

This article received a little bit of dissemination, with the assertion that some apparently futile resuscitations may yet be salvaged despite the lack of cardiac activity on ultrasound.

But, this article doesn't necessarily tell the entire story.  It's a systematic review of several small, poor-quality cardiac arrest cohorts for whom bedside cardiac ultrasonography was performed.  In aggregate, there were 378 patients with no cardiac activity visualized during resuscitation – and 9 went on to have return of spontaneous circulation.  They calculate this out as an LR of 0.18 for ROSC after finding no cardiac activity.

The problem is, this is the only information we have regarding the context of the ultrasound findings or the performance characteristics of the ultrasonographers at work.  The authors also appropriately note that ROSC is not necessarily the ultimate patient-oriented outcome of interest – since we know that most ROSC after cardiac arrest admitted to the hospital still goes on to have a dismal outcome.  

I'm not entirely sure what my takeaway should be from this study, and it's not going to significantly modify my practice.  In the appropriate clinical context, a lack of cardiac activity will still lead me to cease resuscitative efforts.  It would be extraordinarily helpful to have a larger body of data specifically regarding the patient characteristics of those who did have ROSC despite lack of cardiac activity, to see if there is a usable pattern to this small population of exceptions.

"Bedside Focused Echocardiography as Predictor of Survival in Cardiac Arrest Patients: A Systematic Review"

Friday, November 2, 2012

PCA in the ED is Brilliant and Horrible


Management of acute pain in the Emergency Department is frequently inadequate.  Considering the practice environment, the ebb and flow of workload, and the heterogenous presentations, this is not surprising.  On the inpatient side of things, many patients with acute, severe pain receive patient-controlled analgesia.  So, this is a randomized, controlled trial of PCA vs. conventional, untitrated boluses in the ED.

And, they were successful in demonstrating significant trends towards better, faster pain control and increased patient satisfaction with the PCA.  Both groups received the same total amount of morphine, but the dynamics by which patients were able to self-titrate their pain control resulted in improved pain relief.

Unfortunately, there are some flaws with this study.  This multi-center study only managed to enroll 96 patients in a one-year timeframe – probably the number we could aggressively enroll at my institution in a week.  There is no mention of adverse events – which is significant, because PCA medication variances are renowned on the inpatient side as significant sources of morbidity.  And, finally, they don't measure any of the other operational variables that are important – cost, time to set up, etc.

Patient-controlled analgesia may yet have a role in the ED – and studies like this help keep the flame alive – but significant hurdles remain.

"A Randomized Controlled Trial of Patient-Controlled Analgesia Compared with Boluses of Analgesia for the Control of Acute Traumatic Pain in the Emergency Department"
www.ncbi.nlm.nih.gov/pubmed/23068783

Wednesday, October 31, 2012

Arrhythmogenic Right Ventricular Dysplasia

In young Emergency Department patients with syncope, most of the time, testing is minimal.  Generally, the only universal testing is a pregnancy test and/or an electrocardiogram.

We've gotten pretty good at understanding the "life-threatening" causes of syncope in young adults diagnosed by electrocardiography, including:
 - Wolff-Parkinson-White Syndrome
 - Hypertrophic Obstructive Cardiomyopathy
 - Brugada Syndrome
 - Congenital Long QT

But there's always more, and Arrhythmogenic Right Ventricular Dysplasia is one of those "more" that seems not to be on everyone's lists.  ARVD is a genetically-inherited abnormality in cardiac desmosomes that leads to fibrofatty deposition in the right ventricle.  It is currently estimated to result in ~5% of the sudden cardiac deaths in adults under age 65, secondary to sustained monomorphic ventricular tachycardia.  The characteristic EKG finding to look out for is, unfortunately, quite subtle – the "epsilon wave".  These waves are most prominent in V1-V3, and manifest as sharp upward deflections from baseline at the conclusion of the QRS complex.

Very few Emergency Department presentations mix the high-risk needle-in-the-haystack with the low-risk like young adults with syncope, so it's important to stay alert for these rare ECG findings.

"Impact of new electrocardiographic criteria in arrhythmogenic cardiomyopathy"
www.ncbi.nlm.nih.gov/pubmed/23015790

Monday, October 29, 2012

Still Overpromising Benefit of PCI After Cardiac Arrest

The folks in France have been promoting PCI universally after cardiac arrest for quite some time.  It's an appealing concept – when you look at subgroups of out-of-hospital cardiac arrest, there's a significant portion of folks who clearly have a primary cardiac cause, and clearly will benefit from emergency or early PCI.

However, this study inappropriately tries to make the case for all patients to receive PCI and therapeutic hypothermia after out-of-hospital cardiac arrest.  This is a retrospective, cohort study spanning eight years of resuscitation, coordinated between Paris, France and Seattle, Washington.  They used vital records follow-up to determine patient status for each OHCA patient surviving to hospital discharge, and then looked for associations between survival and whether they received PCI or hypothermia in-house.  The most absurd statement is as follows:
"A beneficial survival association was evident among those with and without ST-elevation MI. This finding is provocative given the current debate about whether patients without evidence of ST elevation following resuscitation can benefit from PCI and should undergo early and routine coronary catheterization."
Retrospective studies such as this suffer from substantial selection bias, in which the patients who are selected for particular therapies have interactions and confounders that simply cannot be controlled or adjusted.  Patients benefit from PCI when they have a disease process amenable to intervention – and this is clearly not every cardiac arrest patient. The patients in this study who received PCI – and hypothermia – likely had specific features that identified them to treating physicians as candidates to benefit from these therapies.

The reasonable conclusion from the data presented is exactly that – cardiac arrest patients that have specific features that make them candidate for these therapies will benefit.  PCI following cardiac arrest should not be considered to be "routine".

"Long-Term Prognosis Following Resuscitation From Out of Hospital Cardiac Arrest - Role of Percutaneous Coronary Intervention and Therapeutic Hypothermia"