House of God's Law #3 (Revised)

At a cardiac arrest, the first procedure is to take your own pulse...and nobody else's once CPR is begun. 
(adapted from The House of God by Samuel Shem)

The Gist:  Worldwide resuscitation guidelines de-emphasize pulse checks using palpation due to poor sensitivity and increased no-flow time (1).  Yet, many in-hospital resuscitations still pause compressions for pulse checks, which is associated with poorer survival outcomes (2,3).  New* opportunities exist, taken within the context of the patient, to gauge return of spontaneous circulation (ROSC) including end-tidal CO2 (etCO2) and ultrasound that may lessen interruption in chest compressions.

The Case:  During one of my first official shifts in an ED as a medical student, I participated in a well executed code at Janus General.  Each individual had a clear role and my task was to feel for a pulse.  I kept my hand glued to the patient throughout the code, frightened that I might erroneously call something that was or wasn't actually present.  Eventually, after buckets of fluid, some epinephrine, and sodium bicarbonate (suspected DKA with profound hyperkalemia, which turned out to be the case),  I felt a bounding pulse in our patient and spoke up, still worried that it was the reverberation of my own heartbeat.

This case brought forth three questions, one of which was easily answered:
1.  What about the significance of the time off the chest?

• I've seen a great deal of interruption in chest compressions throughout codes, mostly for transfers or provider switches, pulse checks, and defibrillation.  I began noticing these interruptions more frequently after I discovered that there's a 50% decrease in chance of ROSC for every 10 seconds of hands-off time (4).  I addressed defibrillation here, but pulse checks seem like a non-controversial, more intuitive, and easier means for intervention.

2.  Why aren't we following the guidelines?
3.  Was I crazy to be so worried that I would mis-judge the pulse? We're physicians, surely we can feel a pulse, right?

The FOAM (Free Open Access Medical Education):  On a recent Broome Docs podcast, Dr. Matt Dawson provided reassurance that my fear was not unprovoked.  He recounts a pediatric case in which the discrepancy between cardiac echo and palpation for pulse were not aligned and how that changed the resuscitation.

Do people really still stop for pulse checks?  Yes, and more than we think.

• National guidelines and popular emphasis on uninterrupted CPR may be executed well in the FOAM world, simulation, and many centers; however, chest compressions are still interrupted more than we think. 
•  A recent article by Souchtchenko et al in the Journal of Emergency Medicine articulates this point and provides some points for intervention.  
• We often underestimate interruptions in chest compressions.  This is likely multifactorial, due to recall bias, overconfidence, and cognitive load.  It's easier to gauge CPR quality on the periphery of a code, where our minds have a lessened cognitive load.  Furthermore, it's difficult to accurately gauge elapsed time in such situations, particularly when even a 5 second pause has deleterious consequences on cerebral perfusion pressure (3).  Also, we're more likely to look kindly upon our own skills and actions when we are closer in proximity to the action.   
• A study (n=40 resuscitations) by McInnis et al showed a 30% non-compliance with AHA guidelines regarding compressions and also demonstrated that providers often failed to recognize interruptions in chest compressions.  In a survey, the code leaders explained interruptions in compressions mostly as a result of pulse checks (37%) and defibrillation (24%).  
• Knowledge translation likely plays a role in the discrepancy between what the guidelines recommend and what we practice.  Some community institutions may be more susceptible to slow uptake and implementation of new/changing practices.  Also, CPR is often one of those times in which rescuers run off of their ingrained algorithms, which can be difficult to change in the heat of practice.  
• Equipment/Training.  We may very well know what we're supposed to do, but this may not translate into execution.  Capnography and ultrasound are not available in all resuscitation areas, despite what the FOAM world may have one believe.  

Pulse Palpation Literature: During cardiopulmonary resuscitation (CPR), pulse palpation lacks sensitivity and specificity and typically interrupt chest compressions thus, the guidelines advise against it (1).  According to some studies, only 55% of rescuers can identify a pulse within 60 seconds (6).  Furthermore, most equipment in the hospital allows for rhythm checks during compressions thereby obviating the need for that pause (during which some providers historically integrated a pulse check).  So, even if we're not pausing compressions solely for a pulse check, checking for a pulse may not be that helpful (except to occupy an eager medical student).

Tibballs et al 2010 (full text) was similar to a studies in adults by Dick et al and Eberle et al.

• 209 health care professional "rescuers" were asked whether a pulse was palpable or not in a cohort of pediatric patients receiving forms of extracorporeal life support where some forms generated a palpable pulse while others did not.  Information regarding pressures and pulse forms was obscured
• Pulse palpation: Correct determination 78% of the time.  Rescuer sensitivity 86%, specificity 64%.  Often took up to 30 seconds.
• Limitations: pediatric population, gold standard, site of pulse check, on ECLS (supposedly blinded)

What now?: Ultrasound and capnography (ETCO2) offer ways to predict ROSC with limited to no interruption of chest compressions.  Dr. Reuben Strayer has a detailed cardiac arrest vector demonstrating resuscitation flow with no pulse checks and an Academic Life in Emergency Medicine post offers insight into achieving successful cardiac arrest outcomes.

Ultrasound: This is well-covered by FOAM sources, especially after an article by Blyth et al.  Highlights include the following posts: BestBets (see for landmark articles), EM Lit of Note, ScanCrit.
If you're an EMRAP subscriber, check out the Jan 2013 discussion.

• Lack of cardiac activity on point of care limited echo is associated with poor likelihood of ROSC with a pooled negative LR of 0.18 (95% CI = 0.10 to 0.31), and a positive likelihood ratio of 4.26 (95% CI = 2.63 to 6.92).
• Use the echo in the context of the individual patient/resuscitation. Experts such as Dr. Matthew Dawson suggest that echo be used in two situations: 
• (1) Rule out reversible causes such as tamponade or massive PE.  
• (2) After rounds of CPR as an excuse to cease CPR when resuscitation seems futile (3).
• Limitations:  typically involves interruption in chest compressions, very rare occasions exist when a patient may not have cardiac activity on ultrasound and go on to walk out of the hospital.
• On the horizon? Transesophageal echo during CPR, which limits interruptions but takes far more skill (Blaivas et al).  

Capnography.  There are excellent posts by St. Emyln's, ScanCrit, and a short PK talk by Jon Schonert of EMChatter on this topic so I won't rehash these.

• Given consistent ventilation, the partial pressure etCO2 (PetCO2) correlates well with cardiac output during CPR.  During CPR, the carbon dioxide in the lungs is primary delivered by cardiac output.  
• A rise in PetCO2 to ~35-40 mmHg or a sudden rise of 10mmHg over baseline during CPR has found to predict ROSC (Pokorna et al).  
• Similarly, PetCO2 levels <10mmHg have been associated with unlikely ROSC or need to improve CPR quality. 
• There are limitations to PetCO2 in the context of CPR.  
• Cause of cardiac arrest may alter the PetCO2.  A respiratory cause may increase PetCO2 whereas large pulmonary embolism may cause very low PetCO2 although this is not currently an acceptable diagnostic modality by itself (see this meta-analysis).
• Administration of sodium bicarbonate may increase PetCO2.

*Use of "new" is relative, as literature such as Salen et al is over a decade old.
References:
1.  Berg RA, Hemphill  R, Abella  B, et al.  2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science. Circulation. 2010; 122: S685-S705.
2. Cunningham LM, Mattu A, O'Connor RE, Brady WJ.  Cardiopulmonary resuscitation for cardiac arrest: the importance of uninterrupted chest compressions in cardiac arrest resuscitation.  Am J Emerg Med. 2012 Oct;30(8):1630-8. 
3.  Mattu A, Bond M, Tewelde S, Brady W.  The Cardiac Literature 2010.  Am J Emerg Med.  2012 May;30(4):615-25.  (full text)
4.  Eftestøl T, Sunde K, Steen PA.  Effects of Interrupting Precordial Compressions on the Calculated Probability of Defibrillation Success During Out-of-Hospital Cardiac Arrest. Circulation.2002; 105: 2270-2273. 
5.  Dawson, M.  Comments on Notes from the Community: Cardiac Ultrasound. .Jan 24, 2013.  Available at http://www.emrap.org/episode/2013/january/notesfromthe Accessed June 13, 2013. 
6.Dick WF, Eberle B, Wisser G, Schneider T. The carotid pulse check revisited: what if there is no pulse?Crit Care Med. 2000 Nov;28(11 Suppl):N183-5

You'll shoot your eye out, kid! - Ocular Ultrasound

The Gist:  Ultrasound (US)  training is a vital part of Emergency Medicine (EM) education and may play an even more important role in military, community setting.  Ocular US may prove especially useful in diagnosing and triaging patients with ocular trauma, particularly with regard to retinal detachment in the aforementioned settings.

Recently, EM folks on Twitter debated the utility of ED US in retinal detachment. Those arguing against US dismissed the modality due to the need for an opthalmology consult regardless of the US findings.  This reminded me of a strikingly similar debate I had with a budding PGY-1 ophthalmology resident.  Their arguments have some validity; however, I think it's easy to get swept away in the comfort of 24/7 consults in the academic hospital atmosphere.  This isn't available everywhere, even in the United States, but knowing when emergent action is warranted could prevent serious morbidity.  As the "jack of all trades," EM physicians should probably be prepared for wherever their careers may land them. 

The paper:  Retinal Detachment Due to Facial Gunshot Wound:  The Utility of Ultrasonography in a Medically Austere Environment. in The Journal of Emergency Medicine

• Case report from the military of a patient who suffered a ricochet gunshot wound to the face from an AK-47 who was initially treated for a laceration just inferior to his medial canthus.  Over the subsequent days his vision deteriorated and he was found to have a closed globe with a sluggish pupillary response to light.  Bedside US confirmed retinal detachment and the patient was transported to a combat hospital for ophthalmology care.  He did not recover his visual function in that eye.
• The article is a pretty good read as it succinctly highlights some of the technical aspects of US for retinal detachment with photos and textual descriptions.

This case study suggests:

• Bedside US in the emergency setting can rapidly identify retinal detachments.
• There is likely an incredible role in the battlefield and other remote areas.
• Facial trauma may result in ocular trauma, which isn't immediately apparent and may have permanent deleterious consequences.  Perhaps this patient's vision could have been saved if ocular US had been performed on his first visit.

How do I do this? 

• As always, check out Ultrasound Podcast's amazing Ocular Ultrasound podcast featuring Dr. Chris Fox (Ultrasound Master from UC-Irvine).  Retinal detachment discussion begins at 17:45 .  They've got everything you need to be able to get started with ocular US (and handy instructions on the One Minute Ultrasound app, naturally).
• Pearls from Dr. Chris Fox:  
• Ensure you're dealing with a closed globe and make sure you're scanning with the eyelid closed, of course.
• Use tons of chilled gel (reduces pressure and the high-frequency linear transducer 7.5-10 MHz

What does US really add..besides instant gratification?

• US can differentiate between a "mac on" and "mac off" retinal detachment, which is huge for prognosis.  Instances where the macula of the retina is not detached (mac on) is an ophthalmologic emergency.  If these aren't treated immediately, patient's can deteriorate into a "mac off" detachment, which can result in permanent vision loss (as in the patient featured in the case study).  In resource limited settings or remote areas, this may be an important way to determine patients that must immediately see an ophthalmologist from those who occupy a less precarious situation (sometimes resource allocation is an issue)

    

(Image from Wikipedia)

• Also, ED physicians are pretty good at identifying retinal detachment, with a prospective study (n=48, with 15 EM physicians performing US) demonstrating sensitivity and specificity for RD of 100% (95%CI = 78% to 100%) and 83% (95% CI = 65% to 94%), respectively. 
• US in resource limited settings is feasible and growing in importance so if one is interested in disaster medicine or global medicine, this is a great skill to have.  Check out Mount Sinai's recent US education trip to Haiti, this article discusses US training in Rwanda (and there are many more like it).  

I See Right Through You - Intro to EM Ultrasound

The Gist:  Within the Emergency Medicine (EM) realm, ultrasound (US) is gaining an incredible amount of momentum.  Once relegated solely to use in FAST (focused assessment with sonography for trauma) exams, obstetrics, and placement of vascular catheters, US use and its application are growing in EM.  Keep up by using US often, getting this application, and learning from these guys.

Radiology is boring so why should I care about US?  It takes too much time.  They're just going to get a CT anyways.

• Surprisingly, I occasionally let my "inner nerd" shine.  My discovery of EM US has highlighted this personality attribute, typically when discussing a patient's workup and my suggestion for an ultrasound is met with a scoff or a blank look.  I launch into a giddy medical student frenzy citing recent papers on the risks of radiation and efficiency of bedside US.  This is exciting stuff!  
• Both the medical and lay communities are exploring the burgeoning use of CT scans and the costs and risks associated therein, particularly in younger patients.  Thus, as a no-radiation study, US is gaining ground as a first-line imaging modality.  As a public health student, it's easy to get excited about the ways in which bedside US can help achieve better patient outcomes.
• Immediate gratification.  Medical students seemingly live for the pursuit of test results.  With US, one gets immediate feedback, readily allowing appropriate treatment and disposition.
• Bedside US can be quick.  Many challenge this point, but data are accumulating to suggest that ED length of stay (LOS) can actually decrease with bedside ultrasound by EM physicians. 
• Over a decade ago, a retrospective chart review demonstrated that patients with RUQ pain receiving a gallbladder US by EM residents had a significantly reduced LOS compared with those who had scans in radiology (1).
• Recently, a twitter update alerted me to a study at Sinai where ED US in appendicitis was associated with a decreased LOS  (2). 
• US for deep vein thrombosis by EM physicians also apparently decreases LOS (3)
• The CT scanner is often clogged, probably because between 1/8 and 1/14 patients presenting to the ED in the United States receives a CT scan (4).

But, US is so "operator dependent" and too "technical" for mere students.

• These excuses began this blog in the inaugural post, "Ultrasound for Dummies," a tidbit one might never know due to the tortuous and tangential nature of this blog.  In reality, increased emphasis on excellent US training in the EM curriculum is proving the opposite of these common refrains - EM physicians can perform adequate and timely US.  EBMedicine has an excellent summary of the evidence behind ED US.
• The key lies in hands-on practice...even more reason to get hooked early.
• US training and simulation is growing.  Many medical schools such as UC-Irvine are incorporating US throughout the four year medical school curriculum.  Check this out to see what the EDUS2 project is doing to promote cheap, effective US simulation.
• If the US is equivocal, you may still send the patient to the CT scanner (or perform other imaging/tests).  

Perhaps I'm now slightly intrigued by US...where do I start?

• The absolute first place to start is with the brainchild of Dr. Mike Mallin and Dr. Matt Dawson, Ultrasound Podcast where they "Make Horrible Doctors Decent and Good Doctors Great." (I wonder what they do to medical students?)
• This podcast is entertaining, thorough, and emphasizes the practical application of US in the ED.  Warning: (1) A few portions of the cardiac US lectures are dense and technical - bear through this and keep the podcasts on your phone for future reference (2) Don't listen to this podcast whilst running or driving (the video is key and this could be dangerous) (3) Listening to these podcasts on the elliptical in a public space may be detrimental to your image, as they are prone to make one burst into a fit of laughter.
• Although openly biased, the podcasts provide literature sources for the techniques presented and highlight aspects for future research.
• The free 1 Minute Ultrasound application for iPhone and Droid makes US accessible and quick in the ED.
• UC-Irvine has good, instructive video lectures downloadable via iTunes
• Many EM programs offer US electives for visiting medical students.  I can't comment on the quality of these yet, but I will in the next few months.
• Society of Academic Emergency Medicine (SAEM) has narrated lectures on a few techniques

Looking for a manual-style breakdown of various ultrasound procedures?

• SAEM  has Ultrasound Guides for common procedures in .pdf format and a links to other online resources.
• Ultrasound Guide for Emergency Physicians from ACEP is a little dry but one of the "go-to" resources in EM US training.

But, nobody around here ultrasounds...anything!

• Ultrasound each other.  The EM interest group at my medical school set up some time in the Vascular Sonography program's lab.  Students and instructors from that program were available to introduce us to the world of US.  
• Apparently, extra-firm tofu also works well for a delicious and inexpensive ultrasound simulation (reference #SAEM12).
• Ultrasound is an intellectual epidemic in EM.  However, if you just can't wait until your time in the ED, one can manage to find utility for ultrasound in nearly any medical field.
• For example, on a nephrology rotation, I somehow managed to introduce people to bedside IVC ultrasound and they got excited about doing it.  
• EDs have variable access to bedside US.  Tactfully advocate for improved patient care and outcomes by demonstrating the amazingness of US through the "1 Minute Ultrasound" application or by pandering to an outcome they're passionate about (ex: ED LOS).

Your charm and subtle enthusiasm for ultrasound piqued my interest in US...I want more! (Alternatively:  Supplement to an EM US elective)

• Add the SinaiEM.us blog to GoogleReader
• Case-based learner? Check out a plethora of neat case based videos.
• Ultrasoundvillage.com has an amazing image library, sort-able by organ system
• Search the web for EM US fellowship programs.  Many of these programs have extensive links and resources available, similar to the University of Arizona's list that provide excellent education.
• There are also excellent blog posts at takeokun.com
• The Stanford 25 take on bedside ultrasound, with various monotonic modules from USC. 
• Initiate dialogue with other specialists, students, and attendings on the utility and meaning of EM US.  An easy way to do this is to gift someone the "1 Minute Ultrasound" app...it's the right price for medical students.