No posts for a few! A little busy with the holidays and this little one:
Stay safe, all.
Month: December 2016
Taking Post-Arrest to the Cath Lab
There has been a fair bit of debate regarding the utility of taking post-arrest patients to cardiac catheterization. Clearly, ST-elevation myocardial infarction should receive intervention – although, it can sometimes be challenging to identify on post-arrest EKG. Much less has been determined regarding the treatment of those without STEMI.
This is – as is most of the relevant literature – a retrospective review of patients with cardiac arrest, as identified from a multi-center therapeutic hypothermia registry. These authors record the location of arrest, previously known coronary artery disease, the initial rhythm as shockable or unshockable, and EKG findings. They defined clinically important CAD by the presence of an intervention following cardiac catheterization, including PCI, stenting, or coronary artery bypass grafting.
Entertainingly, the authors hypothesis is “the incidence of coronary intervention would be uncommon (<5%)” – which, if it truly is their hypothesis, it is contradicted by most of their citations, including a meta-analysis citing an overall incidence of CAD in post-arrest patients ranging from 59-71%. Regardless, there were 1,396 patients with known initial rhythms, about 2/3rds of which were non-shockable. About 60% of shockable rhythms and 20% of unshockable rhythms underwent cardiac catheterization. After removing those with obvious STEMI on their EKG, there were 97 patients in their cohort of interest, 24 (24.7%) of whom underwent intervention.
This, therefore, is the “unexpectedly high” incidence of coronary intervention in this non-shockable rhythm cohort without STEMI on EKG. However, as these authors do appropriately note, these data should not specifically inform practice change. The findings in those patients undergoing catheterization are skewed by selection bias, including measured and unmeasured confounders influencing the decision to take patients for potential intervention. In an older population characteristic of a cardiac arrest cohort, some coronary disease is likely on any diagnostic test – and, in this clinical context, it seems intervention would be much more likely than not. Finally, intervention does not equate to a culprit lesion for cardiac arrest, further distancing these results as a surrogate for patient-oriented outcomes.
Despite the “surprise” these authors report, they likely overestimate any evidence for benefit in this post-arrest population, and better characterization of specific high-yield circumstances is needed.
“Incidence of coronary intervention in cardiac arrest survivors with non-shockable initial rhythms and no evidence of ST-elevation MI (STEMI)”
Chest X-Ray Utility in Syncope Lost in Translation
Again, straight out of the ACEP Daily News briefing: “Patients Presenting To ED With Complaints Of Syncope Should Still Undergo Routine Chest X-Rays, Research Suggests.”
This accurately reports the lead of the linked lay medical press article: “ED Patients With Syncope Should Undergo Chest X-Rays”
But, it does not accurately reflect the authors’ discussion or conclusions regarding the utility of chest x-ray in syncope.
This is a retrospective evaluation of patients presenting with syncope and having a chest x-ray between 2003 and 2006 – a secondary analysis of the “Boston Syncope Criteria” study. There were 575 patients included in their analysis, 116 of whom had a defined adverse event within 30 days. Of the patients with positive findings on CXR, 15 of those 18 went on to have an adverse event – and I presume this association led to the perpetuation of this headline.
However, in the greater context: only 18 patients out of 575 had abnormal CXR findings, and even the vast majority of patients with adverse events had normal normal CXR findings. Then, an obvious selection bias should be clear with regard to obtaining CXR in those patients with the appropriate clinical indications – such as a suspicion for CHF or pneumonia. Patients go on to have adverse events because of the morbidity associated with concomitant clinical syndromes, of which the findings on CXR are only one small part of their evaluation.
In short, no, CXR is so low-yield it need not be performed anywhere remotely near routinely in syncope. It may be performed to evaluate a specific presenting symptom related to a syncopal event, but, if anything, these data should indicate it ought be performed less frequently.
“Utility of Chest Radiography in Emergency Department Patients Presenting with Syncope”
http://westjem.com/original-research/utility-of-chest-radiography-in-emergency-department-patients-presenting-with-syncope.html
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”
The Effects of Dilution on Ureteral Stone Passage
In the distant past, I critiqued the Cochrane Review regarding the use of alpha-blockers for ureteral stone passage. I combed through each individual study cited and found, almost universally, they were small, biased, and probably unreliable. Pooling together these poor data, then, was simply a larger pile of junk.
Following the publication of that Cochrane Review, however, were a handful of well-done clinical trials – and they have shown little reliable beneficial effect on stone passage. There was a small inclination towards benefit for those patients demonstrated to have >5mm distal stone disease, but the magnitude of effect was small enough these trials were underpowered to find a difference.
This systematic review and meta-analysis, then, essentially combines this more recent high-quality evidence with the truckload of older evidence from the Cochrane review. With the larger combined sample size, they are now better able to find stronger associations between treatment with alpha-blockers and successful stone passage in these larger stones. Predictably, however, the quality and reliability of their evidence has diminished by simple diluation.
Alpha-blockers are generally benign therapy in ureteral stones, but, if they’re not going to help, they should be avoided. The authors suggest their empiric use should be encouraged, as stone size is not always part of the initial diagnostic evaluation. Most stones are small, however – and the resulting number needed to treat to successfully pass one additional ureteral stone is probably forbiddingly high in such an empiric strategy.
“Alpha blockers for treatment of ureteric stones: systematic review and meta-analysis”
http://www.bmj.com/content/355/bmj.i6112
The Chest Pain Decision Instrument Trial
This is a bit of an odd trial. Ostensibly, this is a trial about the evaluation and disposition of low-risk chest pain presenting to the Emergency Department. The authors frame their discussion section by describing their combination of objective risk-stratification and shared decision-making in terms of reducing admission for observation and testing at the index visit.
But, that’s not technically what this trial was about. Technically, this was a trial about patient comprehension – the primary outcome is actually the number of questions correctly answered by patients on an immediate post-visit survey. The dual nature of their trial is evident in their power calculation, which starts with: “We estimated that 884 patients would provide 99% power to detect a 16% difference in patient knowledge between decision aid and usual care arms”, which is an unusual choice of beta and threshold for effect size – basically one additional question correct on their eight-question survey. The rest of their power calculation, however, makes sense “… and 90% power to detect a 10% difference in the proportion of patients admitted to an observation unit for cardiac testing.” It appears the trial was not conducted to test their primary outcome selected by their patient advocates designing the trial, but in actuality to test the secondary outcomes thought important to the clinicians.
So, it is a little hard to interpret their favorable result with respect to the primary outcome – 3.6 vs 4.2 questions answered correctly. After clinicians spent an extra 1.3 minutes (4.4 vs 3.1) with patients showing them a visual aid specific to their condition, I am not surprised patients had better comprehension of their treatment options – and they probably did not require a multi-center trial to prove this.
Then, the crossover between resource utilization and shared decision-making seems potentially troublesome. An idealized version of shared decision-making allows patients to participate in their treatment when there is substantial individual variation between the perceived value of different risks, benefits, and alternatives. However, I am not certain these patients are being invited to share in a decision between choices of equal value – and the authors seem to express this through their presentation of the results.
These are all patients without known coronary disease, normal EKGs, a negative initial cardiac troponin, and considered by treating clinicians to otherwise fall into a “low risk” population. This is a population matching the cohort of interest from Weinstock’s study of patients hospitalized for observation from the Emergency Department, 7,266 patients of whom none independently suffered a cardiac event while hospitalized. A trial in British Columbia deferred admission for a cohort of patients in favor of outpatient stress tests. By placing a fair bit of emphasis on their significant secondary finding of a reduction in observation admission from 52% to 37%, the authors seems to indicate their underlying bias is consistent with the evidence demonstrating the safety of outpatient disposition in this cohort. In short, it seems to me the authors are not using their decision aid to help patients choose between equally valued clinical pathways, but rather to try and convince more patients to choose to be discharged.
In a sense, it represents offering patients a menu of options where overtreatment is one of them. If a dyspneic patient meets PERC, we don’t offer them a visual aid where a CTPA is an option – and that shouldn’t be our expectation here, either. These authors have put in tremendous effort over many years to integrate many important tools, but it feels like the end result is a demonstration of a shared decision-making instrument intended to nudge patients into choosing the disposition we think they ought, but are somehow afraid to outright tell them.
“Shared decision making in patients with low risk chest pain: prospective randomized pragmatic trial”
http://www.bmj.com/content/355/bmj.i6165.short
tPA For Wake-Up Strokes – “Safe!”
It’s medical news nonsense time again – this time featuring our old favorite, tPA for stroke.
“Tissue Plasminogen Activators Safe for Patients Who Wake Up with Stroke Symptoms” reports HCP Live, and featured in the ACEP daily e-mail newsletter. Oddly enough, this article was actually initially published back in July before being picked up by the health news blog world here in December.
As the headline suggests, this is an article regarding “wake-up” strokes, those with an unknown time of onset because the patient was last seen normal prior to sleep. The authors hypothesize this might represent an otherwise missed, but eligible, population if their stroke onset was close to waking.
But, in this open-label study spanning 3 years of enrollment, there is absolutely nothing conclusive to be said. During this period, across five centers, these authors managed to enroll only 40 patients – the vast majority of whom had NIHSS less than 10, and four of whom were mimics. Following treatment, six suffered intracerebral hemorrhage, two developed angioedema, and one suffered systemic hemorrhage – and thus, the apparent conclusion, that tPA is “safe” in this population.
In reality, this hardly tells us anything of the sort – generalizing results from this cohort of mostly small strokes to a larger treatment population is obviously inappropriate. But, the authors state it forms the foundation of future trials – and, no doubt, they are underway already.
“Prospective, Open-Label Safety Study of Intravenous Recombinant Tissue Plasminogen Activator in Wake-Up Stroke”
November EM Lit of Note Audio Digest
Another month, another episode – episode #2, to be specific. Available for download or in iTunes.