Transfusion and the Glycocalyx: John strikes again! #FOAMed, #FOAMcc

A great surprise this morning:  a comment from John. Yup, THE John. So taking a page out of Scott’s book, I thought it would be worth sharing with everyone as its own post, as opposed to just a comment. I think this is must-read material for everyone.

So without any further adue:

“I thought I might add some quirky ideas to your discussion.

We are now getting familiar with the concept of endothelial cells covered by a surface glycocalyx layer, that forms part of the barrier and mechano-sensing functions of the blood-tissue interface. We have discussed in some detail, the role of the glycocalyx in preserving endothelial integrity. I am gonna try and add a bit more spice into the whole transfusion drama.

In recent times, we have started talking a lot about a bioactive phospholipid called sphingosine-1-phosphate (S1P), as a crucial element in preserving vascular barrier integrity by ‘protecting’ the Glycolcalyx. (Most geeky papers on TRALI and other transfusion related complications do mention it).

Because albumin is one of the primary carriers of sphingosine-1-phosphate (S1P), it is possible that S1P, acting via S1P1 receptors, plays the primary role in stabilizing the endothelial glycocalyx. Infact, antagonism of S1P1 receptors have been shown to cause widespread shedding of the glycocalyx, as evidenced by increased serum concentrations of Heparan sulphate and Chondroitin sulphate. (This might probably be one of the mechanisms how albumin is glycocalyx friendly).

RBC transfusions are a double edged sword…..especially in situations of acute anemia as in post hemorrhagic situations ( major GI bleed or trauma.)….I totally agree with you in that the two are conceptually very similar.

Erythrocytes have been identified as an important buffer for sphingosine-1-phosphate . In mice, depletion of plasma S1P by genetic inactivation of S1P synthesizing enzymes (sphingosine kinases 1 and 2) elicits profound pulmonary vascular leak, which can be reversed by restoring circulating S1P via RBC transfusion.

In humans, hematocrit (Hct) predicts plasma S1P levels. There also seems to be a dynamic equlibrium between SIP levels of the plasma, and the circulating RBCs. It has been demonstrated that in anemic individuals, plasma S1P levels are not uniformly restored by RBC transfusion. Rather, the age of the RBC unit at the time of transfusion tended to negatively correlate with the ability of RBC transfusion to replenish plasma S1P. During storage, the S1P content of human RBC markedly declines, likely due to enzymatic degradation. Because erythrocytes serve as a buffer for circulating S1P, aged RBC with low S1P content may be incapable of restoring plasma S1P levels and may actually remove S1P from plasma, which in turn could contribute to increased endothelial permeability, capillary leak, and infiltration of inflammatory cells.

I hope this partly answers your question as to how the glycocalyx may be impacted by inappropriate and irresponsible transfusion triggers. I agree that these are all very novel ideas and as such, exist in the realm of experimental clinical physiology, but my gut tells me that the delicate Glycocalyx may hold the clue to a lot of answers to questions that have plagued us for a long long time!

Cheers,
John from India…”

So first of all, thank you very, very much for reading and taking the time to comment and enlighten us.

As John says, this is still in the realm of experimental physiology, but I think there are a lot of situations we are faced with, perhaps grey zone areas where we debate two potential therapeutic avenues, where we can use some of this data. We might debate giving that extra bit of fluid, or debate crystalloid vs albumin, or blood or no blood with an Hb of exactly 70, and I think we have to start weighing in some of this physiological data, even if it isn’t “evidence-based-by-RTC” to help guide these decisions.

The more I look into it the more it seems that our interventions – particularly fluid resuscitation, needs to be reassessed from the ground up both in nature, quantity and rate of infusion while measuring glycocalyx damage – e.g. biomarkers such as S1P, heparan or chondroitin sulfate, etc…

I’ve previously posted and podcasted about my general strategy for fluid resuscitation, and I am definitely in the process of revising it, still unsure what is best. I’d love to hear how John resuscitates his patients…

thanks!

Philippe

Other Comments:

Mystery John has an uncanny ability to describe complex physiology in the simplest way possible. I am very interested in digging more into his predictions of the possibility of aged erythrocytes removing S1P from circulating plasma.

Dr. John, if you’re out there, could you point us all to some of these studies you’ve mentioned? Any good S1P review papers you’d recommend to those, like me, who are S1P novices?

Thanks for your input! It was a pleasure.

Warm regards,

Derek

Thank you Derek, for the kind comments…. I think the concept of S1P is still in the process of evolving and assuming a definitive shape, so a good review might be hard to stumble across.

A good research article which cites some excellent references might be —

Synergistic Effect of Anemia and Red Blood Cells Transfusion on Inflammation and Lung Injury
— Anping Dong et al. (It is open access at http://dx.doi.org/10.1155/2012/924042).

Hope this helps……

John.

Here is the article:

924042

P

CCUS 2014 – Ultrasound Enhanced Physical Examination: mark your calendars! #FOAMed, #FOAMcc

We’re in the final stretch of planning for this year’s conference, which will be totally awesome:

CCUS 2014 Master Programme

There are a couple of TBA lectures pending confirmation, as well as finalization of the pediatric side, but this should whet your appetites! Final one will be out by the end of the week!

Montreal (awesome spot to visit!) May 9th (pre-congress courses) 10th-11th (main symposium) filled with some really cool clinical lectures on how to integrate ultrasound in common and critical clinical scenarios.

The faculty is awesome:

Andre Denault, Haney Mallemat (@criticalcarenow), Vicki Noble (@nobleultrasound), Mike Stone (@bedsidesono), Edgar Hockmann, JF Lanctot and Maxime Valois (@EGLS_JFandMax), Robert Chen, Catherine Nix, Ashraf Fayad, Michael Woo and many more….

…and lots of intense workshops!

This isn’t just a “how to”, its a “how to really integrate in into daily practice.”  or maybe “how to take your game to a whole new level!”

Registration is open, and figure on the final programme to be out by the end of next week.

http://ccusinstitute.org/Symposium6.html

if you have any questions, feel free!

Hope to see you all there!

Philippe

A Paradigm shift: re-thinking sepsis, and maybe shock in general… #FOAMed, #FOAMcc

Thomas Kuhn, physicist and philosopher, in his groundbreaking and science changing text, The Structure of Scientific Revolutions, states that:

“Successive transition from one paradigm to another via revolution is the usual developmental pattern of a mature science.”

In other words, a science has growing pains and is bound to have a fair bit of debate and controversy, until a new paradigm becomes dominant.  I think that there is a current – in part prompted by the power of socio-professional media which has allowed minds to connect and knowledge to spread – that will see many of the things that are now “Standard of Care” out the door.

So first of all, the following are must-listens, the first a lecture by Paul Marik, whom I have had the chance to collaborate with in the last years and respect greatly, on knowledge, experience, and even more on his refusal to take anything for granted and being in a seemingly-constant quest for the improvement of medicine.

The second link is Scott Weingart’s take on it, which I think is equally awesome.

I think Paul is pushing the envelope in an essential way, and Scott does a fantastic job of seeing or putting it in perspective. Enjoy:

http://emcrit.org/podcasts/paul-marik-fluids-sepsis/

http://emcrit.org/podcasts/fluids-severe-sepsis/

My (very) humble opinion on this is a rather simple, almost philosophical one:  why are we seemingly obsessed with treating a predominantly vasodilatory pathology with large amounts of volume?  I’ve said this in previous posts and podcasts, but this, in my opinion, is largely cultural and dogmatic. “Levophed – Leave’em dead” is something I heard as a student and resident, and came to take for granted that I should give lots of fluid in hopes of avoiding pressors… But there’s no evidence at all to support this.  The common behavior of waiting until someone has clearly failed volume resuscitation before starting pressors befuddles me (think how long it takes to get two liters of fluid in most ERs…).  If I was in that bed, I’d much rather spend an hour a bit “hypertensive” (eg with a MAP above 70) than a bit hypotensive while awaiting final confirmation that I do, in fact, need pressors.

I strongly suspect that it’s just a matter of improving vascular tone, giving some volume (which may be that 3 liter mark), and ensuring that the microcirculation/glycocalyx is as undisturbed as possible. Now when I say it may be the 3 liters, I firmly believe this will not apply to everyone, and that it will be 1 liter in some, and 4 in others, and that a recipe approach will be better than nothing, but likely harm some.

I think that blind (eg no echo assessment) of shock is absurd, and for anyone to propose an algorithm that does not include point-of-care ultrasound is only acceptable if they are in the process of acquiring the skill with the intention of modifying their approach in the very near future.

The whole microcirculation/glycocalyx is absolutely fascinating stuff, and undoubtedly will come under scrutiny in the next few years, and it is definitely something I will focus on in upcoming posts & podcasts. Our resuscitation has been macro-focused, and certainly it is time to take a look at the little guys, who might turn out to have most of the answers. For instance, there is some remarkable data on HDAC inhibitors (common valproic acid) and their salutatory effects in a number of acute conditions such as hemorrhagic shock (Dr. Alam) which have nothing to do with macro-resuscitation, and everything to do with cell signaling and apoptosis. Hmmm…

please share your thoughts!

thanks

Philippe

NEJM Circulatory Shock Review by Vincent & DeBacker: the sweet and the not-so sweet… #FOAMed, #FOAMcc

So if anyone hasn’t read it, here it is:

https://dl.dropboxusercontent.com/u/12364741/Circulatory%20Shock%20-%20NEJM%202013.pdf

I read the article by critical care icons Dr. Jean-Louis Vincent and Dr. De Backer with interest  as I am always keen to find out what the cutting edge is… So here is my take on their review.

The not-so-sweet:

The inclusion of CVP in the assessment. Ouch. No evidence whatsoever. Evidence for lack of correlation to fluid responsiveness… I wonder if they themselves were cringing a little about including it, particularly form the fact that they just put high vs low rather than commit to a value, which makes me think they realize it’s a bit of a trap. (It reminds me a bit of those night-time orders I still sometimes see which say if u/o < 30 cc/hr give a bolus if CVP under 12 or lasix if over 12.  So basically depending on whether that patient’s head is elevated, or if he’s turned on one side or the other, he may go from “needing fluids” to “needing diuretics”…).

The sweet:

First of all, they obviously did an elegant job on description of shock states, and particularly of highlighting the common-ness of mixed etiology shock.

I like that they admitted that the end-point for fluid resuscitation is “difficult to define.”  Any answer other than that would really speak to non-physiological thinking, as I’ve referred to in prior posts/podcasts.

Dopamine: good job on trying to take it off the shelf for shock. As far as I’m concerned, only useful when you’ve run out of norepinephrine, although there is the odd time when you have a septic AND bradycardic patient where it could come in handy…

Bringing some focus on the microcirculation: no recommendations, but that’s appropriate since there are none to be made yet, but this is where the money is in the future, as far as I’m concerned. Once we figure out how to manage the microcirculation (we do ok with the macro circulation) we might forge ahead. But good to point the finger in that direction.

The super-sweet!

I do (not surprisingly) really, really like the fact that they included ultrasound in their assessment protocol, and emphasizing that focused echocardiography should be done as soon as possible.  Very nice. Finally.

Hopefully, this pushes mainstream ED and critical care physicians to realize they need basic bedside ultrasound skills…

 

Overall, I think it is a good review, certainly worth the read for trainees. I would like to see focus on re-examining and questioning our approach, which could spur readers to embark on research with a different angle. For instance, why do we assume that we need to fill patients to the point of no longer being fluid responsive in order to avoid vasopressors? Is there any evidence for that? Not that I know of…

But, for having put an emphasis on point-of-care ultrasound, it gets a big round of applause from me!

 

Philippe

Bedside Ultrasound Clip Quiz 2 – #FOAMed, #FOAMcc

64 yr old woman POD#3 Rt heimcolectomy with fever and abdominal pain.

Right costal longitudinal scan. What do you see?

 

 

 

 

 

 

 

 

A complex echogenic sliver of ascites over the liver…now what do you do? Here’s what I did…

 

…and it showed fecaloid material. Turned out to be anostomotic leak.  Didn’t have to push much for surgery.

 

Philippe

 

Bedside Ultrasound Picture Quiz 1 #FOAMed, #FOAMcc

A 70 year old man with cough and fever…what do you see?

Right costal coronal view

 

scroll down for an answer!

 

 

 

 

 

Rt CCV labelled

 

The ultrasound diagnosis is of a consolidation with a small pleural effusion.  This can be referred to a “hepatization” as the appearance becomes quite similar to an unaerated organ. A sonographic air bronchogram is seen as well. Clinical correlation with the history and bloodwork strongly suggests a pneumonia.

Case Studies in Bedside Ultrasound

I’ll soon start putting up interesting bedside ultrasound loops and images (as soon as I can get this software figured out…), in the meantime, if anyone is interested, we have a casebook  which can be found on the CCUS website (http://www.ccusinstitute.org or an e-version on iTunes (https://itunes.apple.com/us/app/50-case-studies-in-bedside/id599201706?mt=8).

thanks!