Shock Macro and Micro-circulation: Piecing things together. (Part 1) #FOAMed, #FOAMcc

 

So I have really, really enjoyed the discussions I had with these bright people on shock circulation:

Segun Olusanya (@iceman_ex) Resus Track 2

Rory Spiegel (@EMnerd) Resus Track 3

Korbin Haycock (tell him to get on twitter) Resus Track 4

Jon Emile (@heart-lung)  Resus Track 5

 

Some take home points so far:

I think that more questions than answers truthfully came out of this, and that is really the best part. But lets see what the common agreed upon thoughts were:

a. the relationship between the MAP and tissue perfusion it quite complex, and definitely not linear. So scrap that idea that more MAP is more perfusion. Could be more, same, or less…

b. you can definitely over-vasoconstrict with vasopressors such that a increasing MAP, at some point, can decrease tissue perfusion. Clinically, we have all seen this.

c. no matter what you are doing theorizing about physiology and resuscitation, THE MOST IMPORTANT IS TO CONTROL THE SOURCE!

 

Some of the interesting possibilities:

a. Korbin sometimes sees decreasing renal resistive indices with resuscitation, particularly with the addition of vasopressin.

b. the Pmsa – can this be used to assess our stressed volume and affect our fluid/vasopressor balance?

c. trending the end-diastolic velocity as a surrogate for the Pcc and trending the effect of hemodynamic interventions on tissue perfusion.

This stuff is fascinating, as we have essentially no bedside ability to track and measure perfusion at the tissue level. This is definitely a space to watch, and we’ll be digging further into this topic.

 

Jon-Emile added a really good clinical breakdown:

I think one way to think of it is by an example. Imagine 3 patient’s MAPs are 55 mmHg. You start or increase the norepi dose. You could have three different responses as you interrogate the renal artery with quantitative Doppler:

patient 1: MAP increases to 65 mmHg, and renal artery end-diastolic velocity drops from 30 cm/s to 15 cm/s
patient 2: MAP increases to 65 mmHg and renal artery end-diastolic velocity remains unchanged.
patient 3: MAP increases to 65 mmHg and renal artery EDV rises from 10 cm/s to 25 cm/s

in the first situation, you are probably raising the critical closing pressure [i know i kept saying collapse in the recording] relative to the MAP. the pressure gradient falls and therefore velocity falls at end diastole. one would also expect flow to fall in this case, if you did VTI and calculated area of renal artery. in this situation you are raising arteriolar pressure, but primarily by constriction of downstream vessels and perfusion may be impaired. ***the effects on GFR are complicated and would depend on relative afferent versus efferent constriction***

in the second situation, you have raised MAP, and probably not changed the closing pressure because the velocity at the end of diastole is the same. if you look at figure 2 in the paper linked to above, you can see that increasing *flow* to the arterioles will increase MAP relative to the Pcc [closing pressure]. the increase in flow raises the volume of the arteriole which [as a function of arteriolar compliance] increases the pressure without changing the downstream resistance. increasing flow could be from beta-effects on the heart, or increased venous return from NE effects on the venous side activating the starling mechanism. another mechanism to increase flow and therefore arteriolar pressure relative to the closing pressure is the provision of IV fluids.

in the third situation, MAP rises, and EDV rises which suggests that the closing pressure has also fallen – thus the gradient from MAP to closing pressure rises throughout the cycle. how might this happen? its possible that raising the MAP decreases stimulus for renin release in afferent arteriole, less renin leads to less angiotensin and less efferent constriction. thus, paradoxically, the closing pressure falls with NE! another possibility is opening shunts between afferent and efferent arterioles [per Bellomo]. as above ***the effects on GFR are complicated and would depend on relative afferent versus efferent resistance changes***

 

This is really, really interesting stuff. So in theory, the MAP-Pcc gradient would be proportional to flow, so if we can estimate the direction of this gradient in response to our interventions, we may be able to decrease iatrogenism. I’ll have to discuss with Jon and Korbin which arterial level we should be ideally interrogating…

More to come, and next up will be Josh Farkas (@Pulmcrit), and I’m sure anyone following this discussion is looking forward to what he has to say. I know I am.

cheers!

 

Philippe

The Resus Tracks 05: Kenny (@heart_lung) Tackles Shock Perfusion! #FOAMed, #FOAMcc, #FOAMus

So finally got around to corralling Physiology Jedi Master Jon-Emile Kenny for a chat, which is always a tremendous learning opportunity. And this time was no different. Jon breaks down some of the mysteries around arteriolo-capillary coupling and shock flow, and brings up some really interesting potential uses of the critical collapse pressure of small arterioles, and hints at how we may be able to use some POCUS techniques to clinically assess tissue perfusion.

Here you go:

Please leave comments and questions!

The article we refer in the beginning to is here:

MAP in sepsis review

And the article on critical closing pressure in the neurocirculation that Jon refers to is here:

CrCP Brain

cheers!

 

Philippe

The Resus Tracks 04: Shock Circulation & Renal Perfusion with Korbin Haycock. #FOAMed, #FOAMer, #FOAMus

 

So I got to have a chat with ER doc extraordinaire Korbin Haycock today, reasserting my belief that tissue perfusion is not proportional to blood pressure.  I am again including the article discussed, and here is the graph in question:

Here is our talk:

And the paper – which is definitely worth a read, as it clearly supports individualizing therapy!

MAP in sepsis review

 

cheers and please jump into the discussion!

 

Philippe

The Resus Tracks 03 – Shock Circulation with @EMnerd! #FOAMed, #FOAMcc, #FOAMer

Here we go!

 

Discussing with Rory is always awesome, because he manages to distill things to the most important stuff. In this one he basically says sure Phil, it’s fun to think up all kinds of semi-theoretico-imaginary hemodynamic stuff, but you gotta make sure you control the source!

Thanks!

 

Love to hear comments and criticisms!

 

Philippe

 

Here is the open access paper I was talking about, graph on page 2.

MAP in sepsis review

 

POCUS & Venous Congestion – A Clinical Case Discussion with Rory Spiegel (@EMnerd_), #FOAMed, #FOAMus, #FOAMcc

Hi, so as a follow up to our earlier discussion, which can be found here, Rory and I discuss a recent case he had, which I think exemplifies well many of the clinical conundrums that are seen in fluid resuscitation, one being the general resistance of many to diurese patients who are still in shock on vasopressors, instead preferring to (hopefully) wait until shock resolution to de-resuscitate. But sometimes, it is exactly what they need, as some of this congestion may be, in fact, a cause of shock…

Here you go:

Love to hear opinions, so feel free to reach out.

 

For those who may be interested at learning some of these POCUS skills, check out H&R2018 (#Hres2018)!

 

cheers!

 

Philippe

H&R2018: Final Program! Only a few spots left!

Do you take care of sick patients?  If so, you’ll be liking these two days.

Jon-Emile Kenny, Rory Spiegel, Josh Farkas and Andre Denault in the same, small auditorium. It’s a treat.

So here is the schedule for both days, including the workshops, which at this point are almost filled. We’re quite excited as it has really come along well, and all the speakers are amped to teach and learn, which is the point of this whole thing.

 

Due to fire code, space is limited so register now! And honestly, the workshops are almost full, but if there is sufficient demand, we might add one or two, so don’t be shy. Someone even asked for a Neuro-POCUS workshop. A couple more inquiries and we’ll do it!

Download the brochure and registration form here: H&R2018 – Brochure-Participants

 

Thanks and see you in Montreal in April!

 

The Scientific & Organizing Committee

The Hospitalist & The Resuscitationist. Montreal, April 18th & 19th, 2018. #Hres2018

NOTE: THIS WAS THE H&R2018 PAGE, SO IF YOU ARE LOOKING FOR H&R2019, CLICK HERE!

So for this winter, we’ve put together a little gem of a conference which will be a mix of hospitalist and critical care medicine, both with a dash of POCUS for good measure. Our focus here will be short, to the point, highly relevant and highly physiological talks on key topics, in short, 15 minute talks.

What are we going to talk about?

Day 1: The Hospitalist

 

Day 2: The Resuscitationist

 

 

You can figure there will also be late-breakers, “ask the crowd” talks and more.

Workshops? Sure:

Yup. You can ask for a workshop. Enough similar requests will probably make it happen. A few have already asked for Neuro-POCUS, so that is a likely addition.

 

So, who will be talking?  The lineup already includes Andre Denault, Josh Farkas (@Pulmcrit), Jon-Emile Kenny (@heart_lung), Rory Spiegel (@EMnerd), Hussein Fadlallah, Peter Barriga, Daniel Kaud, Davide Maggio, Michael Palumbo, William Beaubien-Souligny, and a few more to confirm. And who knows who might do an impromptu drop-in…

 

The short answer is yes. Of course, it does depend on what you do. If you are a hospitalist, involved in critical care or acute care of any kinds, you will find something here for you. Totally awesome for IM residents/FM residents planning on doing some hospital medicine or ICU coverage. Who will get the most bang for his or her buck here? Real docs training or working in the trenches. This isn’t a cutting edge research conference, but a cutting edge clinical application conference.

 

Oh yes, and the CME, of course:

 

This will be a small, fun conference. Space is purposely limited, for an intimate feel and to encourage discussion between peers. No need for these exclusive “meet-the-professor lunch” or anything like that: that’s what the whole event is like!

 

Registration is open! Print, fill, write a cheque and send the form below:

RegistrationV2

If you’re crazy busy, or have any questions, feel free to email hospresusconference@gmail.com or tweet (@ThinkingCC) to reserve a spot! 

Download the brochure here:

H&R2018 Brochure – Participants

 

cheers!

 

The H&R 2018 Scientific & Organizing Committee:

Dr. Philippe St-Arnaud – ER and Critical Care doc, POCUS instructor and constantly pushing the clinical envelope.

Dr. Carola Zambrana – our Hospitalist on the panel, constantly seeking excellence in care and working on bringing POCUS to the wards.

Dr. Mario Rizzi – our friendly neighborhood respirologist and educator.

Dr. Philippe Rola – Critical Care doc, long time POCUS aficionado and instructor, working at bringing POCUS into the everyday physical exam.