So managed to pin another really bright guy down today and get his thoughts. Of course we digress some, but I think in all the topics that are truly important to sepsis resuscitation.
So I think all the resuscitationists I have spoken to tend to hover around the same common points:
- lactate is a marker of severity of insult/injury/inflammation but NOT something to specifically treat with an automatic fluid “chaser.”
- getting a global assessment of the patient’s perfusion – including things such as CRT is important.
- a strategy that seeks to exterminate fluid responsiveness is non-sensical and pathological.
The nice thing for our southern neighbours is that this study may give you a solid excuse to shake off that lactate mandate.
And I think that Korbin’s ending remarks are important, and it is something I try to teach residents, that there is little value in rapidly normalizing hemodynamic values – which treats the medical team very well – if there is an aftermath that is not beneficial for the patient. Kathryn Maitland’s FEAST study is the real groundbreaker for that concept. So probably a coordinated and careful ground assault is better than dropping the nuke.
For more discussion on this trial check out Rory Spiegel’s breakdown at https://emcrit.org/emnerd/em-nerd-the-case-of-the-deceitful-lantern/ and our discussion at https://thinkingcriticalcare.com/2019/02/19/the-andromeda-shock-study-a-physiological-breakdown-with-rory-spiegel-emnerd-foamed-foamcc-foamer/
a couple points:
First, much thanks to Scott Weingart whose technical pointers are improving my audio quality! Still a ways to go but on the path!
Second, if you’re not registered for H&R2019, there’s only about 20 spots left. And only a handful for the much-anticipated Resuscitative TEE course. Don’t miss out. If you enjoy these discussions, there will be plenty of that, especially in the protected meet-the-faculty times.
And finally, though he doesn’t yet have a blog, you can now follow Korbin on twitter @khaycock2!
So here is what Jon tweeted a couple weeks ago:
Yikes! Does that spell doom for POCUS???
So clearly we had to get to the bottom of this statement…So a google hangout was in order.
Part 1 my intro:
and Part 2 our discussion:
So the bottom line is that we agree that there is a risk that POCUS may partly head the way of the PAC, or at least be challenged in a similar fashion. Hopefully the wiser physicians will see the inherently flawed logic that would push the field in that direction. Alternately, we could all get our minds and efforts together and try to do a triangulation of data to really pinpoint hemodynamics.
Love to hear comments!
For more of Jon’s physiology awesomeness, visit http://www.heart-lung.org.
PS for cutting-edge and bleeding edge discussions, including Jon-Emile and a lot more, don’t miss H&R2019 this may in Montreal…
So I just finished reading the CHAISE study, which compared Parm as a surrogate for Pmsf as a surrogate for “volume status.”
It is a really cool study for anyone who loves physiology, which I definitely do, and there may be some interesting elements that can be clinically used.
But let’s first set the record straight. I do not believe that “volume status” is a medical and especially not a scientific term. It is a vague reference to intravascular fluid and can be interpreted in a lot of different ways, making it essentially useless. There is such a thing as the status of your flight (on time, delayed, cancelled), your reservation (confirmed, cancelled), your postal delivery (returned, delivered, in-transit), etc. But there are no such clear strata for “volume status.”
So what are the true scientific terms that can be measured? Blood volume. So if we had a bedside radiolabelled substance test that could give us our true blood volume, that could give us a real measure of “volume status.”
On the other hand, that would be of marginal use clinically, in all likelihood.
Why? Because there are only three questions that the savvy clinician is trying to answer, in order of importance:
1. Does my patient need fluid?
2. Is my patient volume tolerant?
3. Is my patient volume responsive?
The answer to the first question is mysterious, outside of the obvious extremes, and in my opinion, anyone who feels they can clearly answer correctly is deluding themselves.
The answer to the second question is complex and multi-factorial and includes echographic findings (venous congestion/hypertension, B lines, effusions, ascites) as well as physical examination findings (tight abdomen, edema) and clinical findings (respiratory failure, intracranial pathology) and more. But this is a critical one, because if the answer is no, then you need some really compelling evidence to even consider trying to answer the third question.
The answer to the third question is, outside of the extremes, a bit of a quagmire of assessments and technology with generally poor evidence, particularly in terms of duration of effect. The most fearsome aspect of this third question is that it is usually the first question asked instead of the last, and thus has the side effect of creating volume-responsiveness terminators who, 500cc shot after 500cc shot end up satisfied that they have blasted responsiveness into oblivion.
But that’s probably bad news for the patient, that they have now pushed into venous congestion or salt-water drowning. Unless, of course, they just look for volume-responsiveness in the same way that bird-watchers do, for the sake of scientific satisfaction, and do no more than look, or maybe snap a picture at most.
So sure, echocardiographic parameters for volume status should be under fire, as all other parameters should. The authors in this paper themselves state two critical assumptions in the Parm/msf logic:
(1) that the fluid stay intravascular in the 10 minutes (ok, I’ll buy that)
(2) that the compliance is linear (nope, I don’t buy that, especially not in sick patients on vasopressors – as opposed to the normal cardiopulmonary and hemodynamic patients this study was done on).
Essentially, what should be under fire is the obsession with a measurable variable to assess intravascular volume. Too many factors in play, and the answer is useless clinically anyway.
On the other hand, this study is fascinating in terms of what might be done using dynamic Parm… Maybe individualizing pressor response, unstressed volume recruit-ability? I’ll let @iceman_ex tell us about that at H&R2019!
So what is important is stop points. And reverse points. And yes, these can be looked at using POCUS, and also CVP, and CVP tracings. And yes, there is good data that venous hypertension is a bad state. And this is what you should be looking at, to make sure you have not pushed your patient into a universally pathological state of non-volume-responsiveness.
So Kylie (@kyliebaker888) had some comments and questions:
Hi Philippe, I just had to read the article after your blog. Most is a bit above my head (yeah right Kylie)– but I am perplexed by three things that I did understand -perhaps you can help me with….
1. Is P(arm) a useful measure? – it went up in 19 patients and down in 8 patients after a 500ml bolus yet they claim it went up (after statistical repeated measures or something)..if P(arm) is confounded by something else – I think they suggest sympathetic tone – shouldn’t we sort that before we start using P(arm) as a reference test.
I don’t think we can consider it to be a reference at all. I think it is an interesting physiological measure and that it might have some application in phenotyping vascular tone/compliance and possibly helping in vasopressor fine tuning. In my opinion for fluids it adds little to what we have.
2. What do you think of their IVC measure – 0.5cm below junction with RA?
As I do for all IVC diameter measures, I think it is inherently mathematically flawed to try to assess a volume using a diameter. Eyeball the whole IVC. A recent study finally looked at this. 3D IVC assessment and (of course) found it better.
3. What do you think of the fact that E changed, but e prime and E/e prime didn’t….That seems like there may not be enough precision in some of those measurements.
I also have another savvy-clinician question to add to yours
Q4: Is my patient leaking?
Jon, great post as always! I do agree with most of it, but would have to caution readers about reading it with the filtered glasses that make people too often take home the message that they want to – usually the path of least resistance (or change). I think your main point and most critical one is that there is no protocol or recipe that should ever be applied to resuscitation, especially single-variable-based resuscitation (eg old school orders like CVP>12 lasix and <12 bolus), and substituting the IVC for CVP won’t help. And from a standpoint of volume-responsiveness, I totally agree, with the understanding that as the IVC gets more plethoric, the percentage of responsive patients will decrease, inevitably, but one cannot predict with certainty whether that one patient will or will not. However, the parallel change is that, as the IVC gets more plethoric, the volume tolerance is likely decreasing as well, so that your benefit to risk ratio is dropping. And of course you can’t recipe that just based on IVC, but should be looking at the site of pathology (eg lung, brain abcess, pancreatitis with ACS, etc…), physical exam, to determine your patient’s volume tolerance. Because we all know that most of that miraculous fluid will end up clogging the interstitium, with consequences ranging from cosmetic to fatal (though usually blamed on the patient being “so sick” in the first place, absolving the clinician from any wrongdoing). So comments like the one previous to mine, stating “give volume and see if the response occurs” are, in my mind, a poor approach. We know from studies that you cannot simply remove the fluid you gave and go back to the start with lasix (glycocalyx damage, etc), and we also know that much of the effect of said fluid administration dissipates in minutes to hours (I’m sure Jon can quote these studies off the top of his head!).
As we have discussed in the past, I think POCUS is much underused as a fluid stop point – most of its use is on the ‘let’s find a cool reason to give.’ I would argue that you should hardly ever give fluid to a full IVC (especially if markers of pathological congestion are present – portal vein pulsatility and all), unless you are dealing with temporarily improving tamponade or tension pneumo, because even if you are volume responsive, you are likely not volume tolerant. This also goes to the point that a single, initial POCUS exam will potentially not have the same impact as a whole POCUS-based management which will use it to reassess congestion status, cardiac function, etc.
Having said all this, the most important part of the SHOC-ED article is, in my mind, their discussion, which is full of all the important reasons why the final conclusion is not `we don’t need to do POCUS in shock,’ which is what I see happening (similarly to the TTM reaction), as they outline the cognitive fallacy of putting on trial a diagnostic tool whilst the therapeutics are not yet clearly established. Those only reading the abstract or conclusion will actually miss the important points of this study which the authors clearly explain.
In particular, the ‘rare’ instances of tamponade or aortic aneurysm or PE in their series would be diluted out by the sepsis, but for those patients, it would matter. As the authors state:
‘one might argue that even a single unanticipated emergency procedure would justify the use of POCUS in critically ill patients.‘
I would have to wholeheartedly agree.
This event is past. It was awesome. If you really wish you’d been there, you can catch most of it here!
And don’t miss H&R2020!
Registration is open and we have said goodbye to the snail mail process. Fortunately, we are a lot more cutting edge in medicine than in non-medical technology.
We are really excited about this programme, and a lot of it comes from the energy and passion coming from the faculty, who are all really passionate about every topic we have come up with.
The hidden gem in this conference is the 4 x 40 minutes of meet the faculty time that is open to all. Personally I’ve always felt that I learn so much from the 5 minute discussions with these really awesome thinkers and innovators, so wanted to make it a priority that every participant should get to come up to someone and say ‘hey, I had this case, what would you have done?’ Don’t miss it!
CME Accreditation for 14 hours of Category 1.
This programme has benefitted from an unrestricted educational grant from the following sponsors (listed alphabetically):
The Accreditation is as follows:
Here is the Final Programme:
Wednesday May 22 – PreCongress course
- Full day Resuscitative TEE course
FOR DETAILS SEE HERE
2. Full day Keynotable
3. Half day Hospitalist POCUS (PM)
4. Half day Critical Care Procedures (AM)
5. Half day Brazilian Jiu-Jitsu for MDs (AM)
for more details on these pre-conference courses please see here.
Main Conference Programme: H&R2019 Full Pamphlet
Thursday May 23rd Meet the Faculty cocktail! 1900 – Location TBA – BOOKMARK THIS PAGE!
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.