Monthly Archives: April 2015

Have a HEART! And some low-risk chest pain risk stratification, while you’re at it!

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Chest pain is tricky. And scary. The combination of these two things makes it one of the chief complaints that seems to be difficult to work up in a thoughtful way, which minimizes risk to the patient (and provider) while also not overreaching in one’s diagnostic testing and thereby adding additional harms.

In medical school, we learned about the TIMI score as the best way for evaluating chest pain in our patients– however, this score was developed for inpatients on the cardiology service admitted with NSTEMI/UA, not ED patients presenting with chest pain, and has only really been validated in high-risk ED patients. The GRACE score is another one that seems to slightly outperform the TIMI in terms of predicting certain adverse events, but again was not designed for risk stratification of ED patients with chest pain.

So now we have (and have had for a while, this isn’t exactly new – I am more reviewing it for my own benefit) the HEART score, designed to “identify both low and high risk patients for an acute coronary syndrome” in the emergency department. It was not derived from a database, but from “clinical experience and medical literature”, and was then prospectively validated in 2440 patients at 10 sites. When compared to TIMI and GRACE, the c-statistic (or area under the receiver-operator curve) was 0.83 v. 0.75 and 0.70 respectively, showing that it did a better job discriminating patients with higher risk for major adverse cardiac events (MACE) in these patients. Pertinently for the ED physician, it also did a better job ruling *out* badness, with a lower percentage of “low-risk” scorers having an adverse event. With all this in mind, I plan to try to use the HEART score in my discussions with attendings when presented with chest pain patients, and hope that I will not only catch more (and rule out more) badness, but may also help reduce invasive imaging and stress testing in these low-risk patients.

In a recent single-center study, Mahler et al. looked back at patients who had HEART scores of 0-3 (low risk) admitted to an ED-based observation unit (keep the population in mind) and evaluated the impact of this score on their receipt of further diagnostic testing down the line, as well as the incidence of adverse events in this group. They found, unsurprisingly, that these patients were in fact at low-risk for ACS — only 0.5% of patients in this group had an adverse event in the next 30 days (though to be thorough, they had a LTFU rate of 30% which is pretty significant). The surprising, and meaningful to me finding was that they reduced the rate of further testing by 83%, no doubt saving these patients from unnecessary stress and anxiety, potential harms or complications, and costs to both them and the health care system.

This is a very incomplete treatment of chest pain risk stratification, I know, but I hope to add more as I learn and read more about these scoring systems and others, and grow in my understanding of critical appraisal of the literature.

References

Antman EM1, Cohen M, Bernink PJ, McCabe CH, Horacek T, Papuchis G, Mautner B, Corbalan R, Radley D, Braunwald E. The TIMI risk score for unstable angina/non-ST elevation MI: A method for prognostication and therapeutic decision making. JAMA. 2000 Aug 16;284(7):835-42. PMID: 10938172. [PubMed] [Read by QxMD]
Mahler SA1, Hiestand BC, Goff DC Jr, Hoekstra JW, Miller CD. Can the HEART score safely reduce stress testing and cardiac imaging in patients at low risk for major adverse cardiac events? Crit Pathw Cardiol. 2011 Sep;10(3):128-33. PMID: 21989033. [PubMed] [Read by QxMD]
Backus BE1, Six AJ, Kelder JC, Bosschaert MA, Mast EG, Mosterd A, Veldkamp RF, Wardeh AJ, Tio R, Braam R, Monnink SH, van Tooren R, Mast TP, van den Akker F, Cramer MJ, Poldervaart JM, Hoes AW, Doevendans PA. A prospective validation of the HEART score for chest pain patients at the emergency department. Int J Cardiol. 2013 Oct 3;168(3):2153-8. PMID: 23465250. [PubMed] [Read by QxMD]

β-Blockade for the treatment of recurrent VF arrest

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Maybe! In this post, I’ll be looking back at a couple papers that I came across over the last year. One of the more interesting developments in medicine over the last decade in my eyes has been the increasing focus on vagal tone in treating various diseases such as epilepsy and treatment-refractory depression, mostly via the use of implantable devices such as the vagal nerve stimulator (VNS). The mechanisms of action of the VNS in these somewhat-nebulous and poorly-understood pathologies is a murky thing, but the simplified way that I understand it is that you’re calming the body down– putting the foot on the sympathetic nervous system’s proverbial brake, in other words, and this has some beneficial effect. On my ICU rotation, I decided to look into work that has been done on the use of beta-blockade in septic shock patients (coming soon), and during that same month, a few clinicians I had worked with on my away rotation in emergency medicine published a chart review showing the use of beta-blockade in refractory VF cardiac arrest.

The paper on cardiac arrest comes out of Hennepin Co. medical center, and is the work of their new research director, a really cool and smart doc named Brian Driver and some of his colleagues who are very well-known in the emergency cardiology field. They present a retrospective review of 25 patients with refractory VF arrest, all of whom received at least 300 mg of amiodarone and 3 mg of epinephrine and three or more defibrillation attempts (why these numbers?)

Shortcomings of this include the retrospective nature, the sample size, which was small and therefore makes comparisons between these groups useful primarily for hypothesis generation (which is what the authors state), and the use of only one reviewer (presumably unblinded, but this was not addressed). That said, the question itself is a creative one to ask and the neurologic outcomes in the admittedly-small intervention group were excellent– very unusual for something with as high of associated morbidity/mortality as RVF.

Interestingly, the authors provide some historical information reflecting the use of beta blockade to treat cardiac arrest as early as in the 1960s, when the use of propanolol was a second-line agent after lidocaine or procainamide. They also discuss the use of beta-blockade in septic shock patients (as mentioned above– check back in the next couple days for a discussion of those papers) and the idea that dampening the non-beneficial hyperadrenergic state that exists in many critical illnesses may be the reason these studies have shown possible benefit. If any institution is equipped to do this study, it’s Hennepin, and I hope to see more from them regarding this soon.

References

Can the use of tourniquets improves CPR outcomes?

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In my third year of medical school, I was discussing my plan for a heart failure patient in the ED and somehow in the course of our discussion, it got brought up that once upon a time “rotating tourniquets” were used in the emergent management of acute heart failure. This method has long since been abandoned in favor of pharmacological methods of Preload reduction, but still a got me thinking on – I was trying to think about the ways in which  the application of a tourniquet affects physiology. One thought crossed my mind was that a patient with acute heart failure or hemorrhagic shock, or any other low flow state might benefit from a theoretical increase in blood perfusion to vital organs if tourniquets were applied to the limbs. The use of rotating tourniquets in the past in patients suffering from decompensated heart failure might suffice as evidence that this, at least in a time-limited fashion, what at least not be harmful (though I understand that the application of a tourniquet is quite painful, and it would  be necessary to ensure that patients were adequately sedated pain-free if we were to do this).

For some reason, this thought crossed my mind again today and I decided to do a literature search. Unsurprisingly it turns out I am not the only person who has had this idea. Last year a group of Chinese researchers published a paper in which they showed an increase in cerebral perfusion pressure and myocardial blood flow in a porcine model of cardiac arrest. Ten pigs (poor pigs, it is such bad luck that their hearts are like ours)  were assigned to receive standard CPR or  CPR augmented with tourniquets wrapped from the distal to the proximal portion of all four limbs.  Ventricular fibrillation was induced with a pacing wire, and  maintained for seven minutes of “down time” before beginning resuscitation. CPR was performed for two minutes before a dose of epinephrine was given, followed by three more minutes of CPR after which defibrillation was attempted.  There were no significant differences between the outcomes in terms of resuscitation success, number of defibrillation attempts, intra-thoracic pressure, duration of CPR, or the use of epinephrine. What did differ between the groups were measures of cerebral perfusion pressure is measured by carotid bloodflow, systolic and diastolic blood pressures during CPR, coronary perfusion pressure, and end-tidal CO2.  Survival was the same in both groups, but alas, it is difficult to measure neurologic outcome in pigs, so some important end-points were not reported. The differences in CPP were almost 10 mmHg, ETCO2 went from ~ 28 mmHg in the standard CPR pigs to ~36 mmHg in the tourniquet group, and CBF had a ~ 10 mL/min difference (this seems much less clinically-significant to me, but I’m not sure how big of an impact that is– we don’t have this monitor in our ED).

This is obviously a long way away from being ready for prime time in humans, and I’m not sure that you could use this to even get the idea past an IRB.  that said, if you really could improve both coronary and cerebral blood flow, and there were no significant harms associated with this technique I don’t really see the downside of trying– do you?  Some important limitations beyond the animal model  of this study include the relatively short “downtime”, the lack of assessment of function after the resuscitation (even if you can’t measure neurologic outcomes, you could look at cardiac function),  and the fact that there model of tourniquet usage doesn’t really match the way that we use tourniquets and human beings. This may be nitpicky, but the tourniquets were applied during fibrillation, not during CPR– it is hard to imagine that this would be an easy feat to accomplish or get buy-in for outside a setting where you have plenty of free hands. Lastly, these were presumably otherwise-healthy pigs– we really need a porcine model of a more typical cardiac arrest patient if we’re going to try to apply this to humans.

Still, I find this very interesting, who think that there may be a future in trying to use a similar technique in humans eventually. I have seen many “survivors” of cardiac arrest who may have achieved ROSC, but ultimately never made it out of the ICU– these represent the majority of those who survive in and out-of-hospital cardiac arrest– and anything that could potentially improve their most important outcomes, survival of head and heart, would be welcomed. The odds of me being able to do this RCT while in residency? Probably low. But you never know!

References

Yang Z1, Tang D2, Wu X3, Hu X4, Xu J5, Qian J6, Yang M7, Tang W8. A Tourniquet Assisted Cardiopulmonary Resuscitation Augments Myocardial Perfusion in a Porcine Model of Cardiac Arrest. Resuscitation. 2014 Oct 23;86C:49-53. PMID: 25447436. [PubMed] [Read by QxMD]

Outcomes of medical emergencies on commercial airline flights.

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As I get warmed up to this whole attempting-to-post-regularly thing, I’m going to share some articles that I came across during medical school that I found interesting or amusing, along with the more serious stuff that utilizes a little bit more critical thinking– first up is this review article on outcomes of medical emergencies on commercial airline flights, from some emergency physicians at U. Pittsburgh and ECU. The authors reviewed records of in-flight medical emergency calls from five domestic and international airlines to a physician-directed medical communications center over an approximately a two year period and reported the epidemiology of in-flight emergencies, along with some outcomes and some commentary.

The most common chief complaints were syncopal events and GI distress, which is not surprising. There were, scattered amongst the less serious complaints, 38 cardiac arrests and 36 deaths reported, alongside some OB/GYN emergencies (most of which were less than 24 weeks and labeled as possible abortions/vaginal bleeding, with 18% involving labor beyond 24 weeks). Physicians provided the majority of assistance, with nurses and EMTs stepping up to the plate as well. The article also describes the FAA laws on medical control, liability issues pertaining to providing care on-board a flight (the 1998 Aviation Medical Assistance Act includes a Good Sa- maritan provision protecting passengers who offer medical assistance from liability, other than liability for gross negligence or willful misconduct), and offers some approaches to common problems. Also, interestingly, a supplementary appendix contains a list of items found in the “Enhanced Emergency Kit” carried by many airlines, which has a lot more than one might expect to find on an airplane. I am planning on working on an educational project for medical students on EM clerkships involving this list– could be fun.

What this study doesn’t address is something I read somewhere a long time ago about a resuscitation that took place on a plane following an arrest. Two physicians on-board initiated CPR and performed chest compressions for 40 minutes or so and applied an AED, which did not find a shockable rhythm. When they told the flight attendants that they were going to pronounce the patient and terminate resuscitative efforts, they were told that the flight attendants were required by policy to continue CPR until they had arrived back at an airport– I can’t remember the exact details, but I believe they decided that they would keep working on the patient, if only to spare the flight attendants the experience. The anecdote, apocryphal as it may be, raises an interesting question though– who can terminate resuscitative efforts on-board an airplane? The captain? On-line medical control? Any random on-board physician or nurse? I’m not really sure what I would do in such a position, but hopefully (and the data seems to suggest that) it will never come up,

References

Peterson DC1, Martin-Gill C, Guyette FX, Tobias AZ, McCarthy CE, Harrington ST, Delbridge TR, Yealy DM. Outcomes of medical emergencies on commercial airline flights. N Engl J Med. 2013 May 30;368(22):2075-83. PMID: 23718164. [PubMed] [Read by QxMD]

Endings & Beginnings

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A little over a week ago, I was one of thousands of medical students across the United States who participated in the NRMP’s Match process, wherein 4th year medical students find out where they will be heading to train in the specialty of their choosing. In my case, the specialty is Emergency Medicine, and where I’m headed is San Francisco, CA– I was humbled and ecstatic to have matched to UCSF, which after a lot of deliberation ended up being my first choice. Before the Match happened, I interviewed at sixteen programs across the country and genuinely loved things about all of them– I would have been lucky to end up at any of the programs I interviewed at, and am confident that I would have come out of any of them clinically well-prepared. That said, UCSF as a fairly young emergency medicine program at such a well-established research center, in a city like San Francisco, stood out as a place that would be particularly great to spend the next several years learning to rule out the proverbial badness while also beginning the next chapter of my life with my partner Karen and our black labrador Hal. Suffice to say, I’m excited for this next part of my life– I have one rotation left in medical school (radiology), a wedding, and a cross-country relocation to get through, but I’m sure that it will be here before I know it.

As part of my preparation for residency, I am going to attempt something I’ve done a few times before and been historically not-so-great at: journaling. Only now, I feel like I have a specific thing to write about, and a rationale– and the internet makes this much easier. I plan on using this website as sort of a journal club for myself, inspired by one of my former faculty members, Dr. Ryan Radecki who runs his own very well-written and informative blog EM Literature of Note. I hope that it will be useful to myself, as a place to collate my thoughts and to practice critical appraisal of the literature, and that someday it might even be useful to others or allow me to participate more fully in the #FOAMed movement– I have so far been more of a lurker, as my medical student status made me feel reluctant to contribute, and I look forward to trying to add some content.

For my first post, I’ll share something I found amusing and relevant to the interview season– an article from our neighbors in the frozen tundra region (I think?) of Toronto: Rainy Weather and Medical School Interviews, by Drs. Redelmeier and Baxter, of the University of Toronto. They looked at interviewer ratings of just under 3,000 applicants who participated in consecutive medical school interviews  between 2004 and 2009 and examined the relationship of weather to admission committee members’ perceptions of applicants.

What they found is perhaps not surprising, though I think if you asked most people if the weather on a day you interview “mattered” they would have a difficult time quantifying exactly how much– according to these authors, interviewing on a rainy day (operationalized a priori if  government records reflected precipitation– including freezing rain, snow and hail– occurred in the morning or afternoon) conferred a disadvantage equal to a 10% lower score on the MCAT, or Medical College Admissions Test. The disadvantage was translated from a score disparity that was statistically significant (barely, but still!). The authors remark in the conclusion that “magnitude of the specific influence may be modest, but such small differences can be important in some cases because each year there are about 100 candidates who receive a score within 1% of the admission threshold”, and end by reminding us of something important about cognitive biases that we (especially in EM) would do well to remember regarding all biases: “Calling attention to these issues may diminish their impact on judgment.” (For better or for worse, I mentioned this article during an interview or two when the weather was terrible– luckily, it was a sunny day in San Francisco.)

Anyway, I hope to do a lot of reading and writing about cognitive biases and decision-making in this blog, and how we in the ED can use knowledge of biases and common cognitive stumbling blocks to improve our own practice. I hope that I manage to keep up this endeavor, and I hope that eventually it can be of use to others. If you got this far, thanks, and keep checking in– I promise I’ll work on the brevity part of blogging. 🙂

References

Redelmeier DA1, Baxter SD. Holiday review. Rainy weather and medical school admission interviews. CMAJ. 2009 Dec 8;181(12):933. PMID: 19969588. [PubMed] [Read by QxMD]