Wee – What the heck is a Mapleson B Circuit and Why You Probably Shouldn’t Care


There is a really smart anesthesiologist out there called Nicholas Chrimes. He along with his mate Peter Fritz invented the Vortex Approach to Airway Management. He also runs a blog called Clinical CrEd.

He did a post advocating the Mapleson B Circuit as the Ultimate Preox Device

What is the Mapleson B? The Mapleson circuits were used for anesthetics in the good old days. At least in the US, we have move to bigger, and arguably better designs for our operative patients. Many would have thought this device would have been consigned to the trash heap, but seemingly not.

Mapleson Circuit

from anesthesia 2000

My Recommended Approaches

I recommend two approaches to preox: standard and shunt physiology strategies. I outlines these strategies in the paper Rich Levitan and I wrote.

Standard: NRB @ >=15 lpm and NC @ 10-15 lpm for 3 minutes

Shunt Physio: Choose 1

  • BVM with PEEP Valve & NC @ 10-15 lpm
  • NIPPV Ventilator with NIPPV Mask or BVM Mask & NC @ 10-15 lpm

Nick makes a number of arguments as to the superiority of the Mapleson circuit over these standard techniques. His points are excellent, but I disagree with pretty much all of them–I think it becomes a question of perspective.

Automatic Checking

Yes, using the same device for reox and preox makes sure the reox device is there and hooked up, but this for me is an inadequate argument to dispense with NRB/NC set-up.

Multiple BVM Masks

We don’t have these readily available in any ED or ICU I’ve worked in. We have neonate, peds, and adult. Our masks also are not inflatable.


PEEP is good, Mapleson may or may not be a good way to provide this for the reasons I’ve mentioned in the wee, but a BVM with a PEEP valve or a vent are at least as good.


Mapleson may provide this better than BVM, but not as well as a NC, which should be on during any intubation.


No advantage of Mapleson

Low resistance

Maybe this matters, as soon as you put on the PEEP, I can’t imagine this difference persisting

Room Air Entrainment

Release your seal for even one breath and you have blown denitrogenation. Always, always use a strapped system if possible=NRB/NC, NIV mask, or BVM mask with OR straps.

Troubleshooting Leaks

This is the real area in which Nick and I differ. Nick makes the point that a good seal in preox guarantees a good seal in reox–this may be true, but it is unimportant. What I care about is does a bad, one-handed seal in preox mean I won’t be able to reox with the BVM–this is entirely untrue. If I did to an awake patient what I will do to them when asleep and desaturating, they would, quite rightfully, punch me in the face.

Anesthesiologists should use Mapleson B/C; ED/ICU should only use BVM +/- PEEP Valve with two hands and oral airway and a rocking triple maneuver (that no pt should experience if they are conscious) otherwise they should be NIV mask with straps or (BVM mask with straps).

This is the same reason I tell my residents to just train with Macintosh blades.

Primary and secondary leaks are the main thrust of Nick’s love for the old-timey circuits. But all of us have appreciated this easily by squeezing the bag-valve-mask: Easy-squeezy or Hard Squeezy

ETCO2 with a monitor you can see

Is he holding or squeezing?

I can feel compliance with a BVM if I squeezed it, but I don’t unless the pt needs it during reox. But are they squeezing the Mapleson? If they are, they may be doing damage. This study (Anesthesiology 2014;120:326) talks about the myths of Gentle Facemask Ventilation:

>15 cmH20 may be entraining gas into the stomach via the LES (in some patients, even 10 cmH20 may be a problem)

UES will withstand at least 20 cmH20 until NMB at which point again 15 seems to be the number (The latter is why we don’t bag during apnea unless we have to)

Two hands ALWAYS on the mask

Recently, I spent 2 weeks intubating 10-15 patients per day. One hand mask skills got better and better–all for naught.

Train how you want to Fight

Hands free

BVM with a PEEP valve solves equipment issues entirely

ventilator or oxylator

Better BVMS

Lower possible Vt and restriction of Inspiratory Flow Time (Maybe a peds bag is the answer–thanks, Peter. Anaesthesia. 2011 Jul;66(7):563-7 and Resuscitation 1999;43(1):31) and Vt of 500 seems the way to go (Crit Care Med. 1998 Feb;26(2):364-8.)

or Use Ventilator or Use an Oxylator

Now on to the wee…


Best of 2013 – Eight is Enough & Social Media Update


Social Media Update

  • Use either RSS or the email updates feature (find both on the home page)
  • If you have a comment on an EMCrit Podcast or Post, please put it on the blogpost on emcrit.org
  • If you have something pithy to say, use twitter
  • If you have a case or a question unrelated to an EMCrit Podcast or Post, use Google Plus or post to the FOAMcc Google Community
  • If you like being screwed and having your information manipulated, use Facebook


Best of 2013


Niche Sites


Social Media Guidelines

Previous Year’s Best ofs

A Product I Recommend



by Brian Kloss and Travis Bruce

Happy Solstice Everyone! and now on to the Podcast…



Five Minutes with Jon Rittenberger on the TTM Trial


Just posted a wee on the game-changing TTM Trial

Managed to get Jon Rittenberger, MD on the line to discuss the implications. Jon wrote the editorial that accompanied the TTM trial and he is an accomplished Resuscitationist and a clinical leader for the U. Pitt post-arrest management team.

Here are Jon’s thoughts on what we should do with this trial tomorrow. I add my own opinion at the end. In the next couple of weeks, you’ll hear from Stephen Bernard to get his take on the study.

The 2nd article mentioned by Jon is this one:

Kim, F et al. Effect of Prehospital Induction of Mild Hypothermia on Survival and Neurological Status Among Adults With Cardiac Arrest A Randomized Clinical Trial JAMA 2013

Prehospital hypothermia in this study and the Bernard trial has not seemed to pan out. Intra-arrest is still in play however.

My Take as of Now

  • In the setting of advanced post-arrest care, active temperature management, and protocolized neuro-prognostication; the TTM trial demonstrated no significant outcome difference or trend towards outcome difference when patients were cooled to either 33 or 36C
  • Hemodynamics were poorer in the 33C group (This was not mismatching, SOFA-C same on day 1 and much worse in 33C group on day 3; this was a secondary outcome and therefore the study can’t demonstrate if this was a significant finding) [Table S2 Supplement]
  • Complications were less frequent in the 36C group
  • A majority of patients are probably best managed at or near 36C
  • In the neurocritical care literature, 35C seems to offer moderation of intracranial pressure
  • At Janus General, we will target a temperature range between 35-36C for our V-fib, V-tach, and PEA patients in whom we are pursuing an aggressive treatment path
  • Unwitnessed asystolic arrest patients were left out of the HACA, Bernard, and TTM trial. In this group there is little guidance and it may be reasonable to continue cooling to 33C as this group is most likely to have the most severe post-arrest neurologic injury.

Interview with the Lead Author of Trial from the ICN

Matt MacPartlin interviewed Niklas Nielsen, the author of TTM. He is joined by Anders Aneman, one of the local site investigators to discuss this game-changing study.

Other Thoughts

See this great post from the folks at the Intensive Care Network as well.

The folks at St. Emlyn’s offer a  more cautious approach.

Now on to the Wee…


SMACC Back 3 – Simon Carley on Leadership


Now I should be doing a SMACC Back on Roger Harris’ talk on the Right Heart as he surely cast a gauntlet in my path, but that would probably just encourage him : ). Instead, lets talk about…

Simon Carley on Educational Leadership and Subversion

This SMACC-Back deals with Simon Carley’s lecture from SMACC 2013. If you haven’t seen it yet, watch now–it is incredibly good:

The line that resonated with me was,

The first principle of Leadership is Excellence. The most important thing for an educational leader is that they are clinically credible. “Those that can’t do–teach,” is crap in medicine.

So utterly true!


Tangentially, one of my colleagues recommended a book to me entitled, Multipliers: How the Best Leaders Make Everyone Smarter.


Wow, what a horribly misguided tome. To hear why I think this, listen to the wee.

Get your SMACC 2014 Abstracts in ASAP

The closing date for abstracts for SMACC is Friday the 22nd of November

Be part of the action!

Submit here.

Now on to the SMACC Back…


EMCrit Wee – Vasopressin, Steroids, and Epinephrine for Cardiac Arrest


New Study in JAMA:

JAMA. 2013 Jul 17;310(3):270-9. doi: 10.1001/jama.2013.7832.

Vasopressin, steroids, and epinephrine and neurologically favorable survival after in-hospital cardiac arrest: a randomized clinical trial

Mentzelopoulos SD, Malachias S, Chamos C, Konstantopoulos D, Ntaidou T, Papastylianou A, Kolliantzaki I, Theodoridi M, Ischaki H, Makris D, Zakynthinos E, Zintzaras E, Sourlas S, Aloizos S, Zakynthinos SG.

Source  First Department of Intensive Care Medicine, University of Athens Medical School, Athens, Greece. sdmentzelopoulos@yahoo.com


IMPORTANCE:  Among patients with cardiac arrest, preliminary data have shown improved return of spontaneous circulation and survival to hospital discharge with the vasopressin-steroids-epinephrine (VSE) combination.

OBJECTIVE:  To determine whether combined vasopressin-epinephrine during cardiopulmonary resuscitation (CPR) and corticosteroid supplementation during and after CPR improve survival to hospital discharge with a Cerebral Performance Category (CPC) score of 1 or 2 in vasopressor-requiring, in-hospital cardiac arrest.

DESIGN, SETTING, AND PARTICIPANTS:  Randomized, double-blind, placebo-controlled, parallel-group trial performed from September 1, 2008, to October 1, 2010, in 3 Greek tertiary care centers (2400 beds) with 268 consecutive patients with cardiac arrest requiring epinephrine according to resuscitation guidelines (from 364 patients assessed for eligibility).

INTERVENTIONS:  Patients received either vasopressin (20 IU/CPR cycle) plus epinephrine (1 mg/CPR cycle; cycle duration approximately 3 minutes) (VSE group, n?=?130) or saline placebo plus epinephrine (1 mg/CPR cycle; cycle duration approximately 3 minutes) (control group, n?=?138) for the first 5 CPR cycles after randomization, followed by additional epinephrine if needed. During the first CPR cycle after randomization, patients in the VSE group received methylprednisolone (40 mg) and patients in the control group received saline placebo. Shock after resuscitation was treated with stress-dose hydrocortisone (300 mg daily for 7 days maximum and gradual taper) (VSE group, n?=?76) or saline placebo (control group, n?=?73).

MAIN OUTCOMES AND MEASURES:  Return of spontaneous circulation (ROSC) for 20 minutes or longer and survival to hospital discharge with a CPC score of 1 or 2. RESULTS:  Follow-up was completed in all resuscitated patients. Patients in the VSE group vs patients in the control group had higher probability for ROSC of 20 minutes or longer (109/130 [83.9%] vs 91/138 [65.9%]; odds ratio [OR], 2.98; 95% CI, 1.39-6.40; P?=?.005) and survival to hospital discharge with CPC score of 1 or 2 (18/130 [13.9%] vs 7/138 [5.1%]; OR, 3.28; 95% CI, 1.17-9.20; P?=?.02). Patients in the VSE group with postresuscitation shock vs corresponding patients in the control group had higher probability for survival to hospital discharge with CPC scores of 1 or 2 (16/76 [21.1%] vs 6/73 [8.2%]; OR, 3.74; 95% CI, 1.20-11.62; P?=?.02), improved hemodynamics and central venous oxygen saturation, and less organ dysfunction. Adverse event rates were similar in the 2 groups.

CONCLUSION AND RELEVANCE:  Among patients with cardiac arrest requiring vasopressors, combined vasopressin-epinephrine and methylprednisolone during CPR and stress-dose hydrocortisone in postresuscitation shock, compared with epinephrine/saline placebo, resulted in improved survival to hospital discharge with favorable neurological status.


SMACC Back 2 – IVC for Decisions on Fluid Status


Justin Bowra gave a fantastic lecture on the use of IVC ultrasound at SMACC.


Here is the audio, if you want to hear the original lecture:

There was a post on Life in the Fast Lane by Justin as well.

His slides from the talk are here:

Now let’s get to the SMACCing back…

I agree with 90% of Justin’s talk, but as to the other 10%:


Mech Ventilated Patients


Diagnosis of Undifferentiated Shock

Quick look at size and collapsibility gives huge amounts of information

Fluid Responsiveness

Need a strategy for Spontaneously Breathing Patients

  1. Go bronze and give a bunch of fluid until you feel slightly uncomfortable
  2. Then go for the silver and resus until IVC starts to lose easily discernible collapse (20-30%)
  3. If you want to be really cool, at this point go for the gold-use some marker of stroke volume to see if additional fluid will be of benefit (either with empiric add. bolus or passive leg raise). If you want to be lazy, just put them on some norepi at this point.

Now if you use this strategy, you need to look at the operator receiver thingy-me-bobs [sic]

Spont. breathing IVC-CI trials fail due to the misfounded desire for dichotomy.



(Lanspa M et al. Shock 2013. 39(2). pp. 155-160)


Muller ROC

(Muller L et al. Critical Care 2012, 16:R188)

This makes sense as respiratory-dynamic CVP demonstrates the same thing (Shock 2006;26(2):140)

Splint IVC open-Tamponade, Tension PTX, Massive PE, Status Asthmaticus, Right heart disease

Don’t sniff test, don’t tell the pt to do weird abdominal yoga breathing

Fluid Tolerance

IVCCI 15% had good accuracy (92% sens/84% spec) for CHF (Blehar et al. The American Journal of Emergency Medicine 2009;27(1):71)

and (Miller at al. Am J Emerg Med 2012;30:778) showed similar text characteristics.

by all means add in the Lichtenstein Lung Ultrasound, but only if negative when you start

We need more and better Studies

  • Get a bunch of sick patients
  • Do an IVCCI with a cut off of something like 30%
  • Give fluid (500-1000 ml crystalloid)
  • See if there was a 15% increase in SVi with a REAL cardiac output monitor or skilled evaluation of LV VTI
  • AND
  • see if there was a >5 mm Hg increase in arterial line MAP

and now on to the SMACC Down…


SMACC-Back – Myburgh on Catecholamines


One of the best lectures from SMACC 2013 was Dr. John Myburgh on Catecholamines.



Here is the Video Version of the Lecture:

Or you can listen to the audio on the SMACC Feed or in Itunes

Now on to the SMACC-Back…



EMCrit Wee – Is Lactate Clearance a Flawed Paradigm?


A listener, Øyvind S Holen, and the PrecordialThumper both alerted me to an article recently published by Paul Marik and Rinaldo Bellomo:
Lactate clearance as a target of therapy in sepsis: a flawed paradigm

In the paper, they discuss many of the misunderstandings re: lactate and lactate clearance. This wee is my response. I’d love to hear your opinions.

This Post was by

Now on to the Wee…


EMCrit Wee – Janus General and Service Update

Janus General Hospital

Janus General is a virtual hospital where I will set all of my future cases. The inspiration for a virtual hospital comes from my friends at the St. Emlyn’s Blog.

Where to Comment/Question

If it is about a blogpost/podcast, comment here on the EMCrit.org site

If it is a clinical question or discussion, go to the EMCrit G+ Community Page

If it is a quick comment or question, hit me on Twitter

If it is a problem with the EMCrit Site or the CME Site, come to the Contact Page

Direct Link to CME for Each Episode

Starting with episode 97, at the bottom of each post, there is a direct link to get CME:



EMCrit Wee – The Vortex Approach

I recently got an email from the creators of a new approach to airway management

Peter Fritz and Nick Chrimes

What these two gentlemen have crafted is a paradigm called the vortex approach. It is best represented by this diagram:


And here are versions with even more information:

Vortex Cognitive AidVortex-Expanded

I could write about the method, but to do it true justice, it is better to watch this video:

The Shock Trauma Algorithm

Now you folks know I am partial to a modified-version of the Shock Trauma Algorithm for Failed Airway Management. It is bar none the simplest, most effective (and validated) algo I have come across. Or at least it was until I started parsing the Vortex Approach. The reason is that the Vortex Approach encompasses the STC algorithm in a way that is universal to all specialties and settings.


Nicholas and Peter wrote a free ebook about the concept, which is available in a number of formats.



They also have a website set up for the Vortex Approach as well as other projects on their Clinical CrEd Site. The Vortex site also has videos demonstrating the approach in action in both an emergency department and operating theater intubation.


Minh Le Cong did an interview with the two of them on his PHARM podcast site that is definitely worth a listen.

Apps I Liked

I was sent free evaluation copies of 2 IOS applications:

  • The IOS version of PressorDex from the EMRA folks. The pocket-book was good; the app is even better.
  • An application listing the most important critical care papers and a short summary of their impact. The app is called ICU Trials by Sean Kane. The link goes to the free lite version; if you like it buy the full version.

Now on to the Wee…