So this was my comment to my friend Jon’s awesome discussion on the SHOC-ED Trial, which is certainly interesting.
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.
cheers
Philippe
thinking critical care 
thanks for your reply – as always thoughtful and well-taken.
i agree with ultrasound for finding the uncommon causes of shock. these examples seems to permeate twitter and make ultrasound very appealing. because ultrasound is non-invasive, it makes the risk-to-benefit ratio very low for these uncommon but highly-lethal and treatable causes.
but that needs to be compared to the risk-to-benefit ratio of ultrasound for the more common causes of shock – like ‘non-cardiogenic, septic’ etiologies as seen in SHOC-ED. here, “static’ ultrasound [as per the RUSH and ACES protocols] – per SHOC-ED – appears to be neither helpful nor harmful. your read of the discussion is perfect, but i was depressed because it read as if the authors only realized this ex post facto – study of previous monitoring utensils [e.g. PAC] should have pre-warned the authors …
i will take some mild issue with markers of volume responsiveness and tolerance. you are correct on both fronts – but what the data for the IVC reveals – perhaps paradoxically – is that true fluid responders can have a very wide-range of IVC sizes from small to large and unvarying … this was born out in most of the spontaneously breathing IVC papers [airpetian and more recent corl paper] the sensitivity was rather poor.
the same *could* be true for the opposite side of the coin. a large great vein may not mean a volume intolerant patient. i tried to exemplify how that could be so in the illustrative case in my post. an elderly man, with probable pulmonary hypertension and chronic TR who probably “lives” at high right-sided pressures. nevertheless, he likely has recurrent C. diff and is presenting 1. hypovolemic and 2. fluid responsive despite his high right-sided pressures. portal vein pulsatility *could* be quite high in this patient – but he still needed some volume.
the obvious underlying issue here – which I know you are well attuned to – is that a Bayesian approach is imperative. when you PoCUS your patients, you are inherently taking this into consideration – i know that you are a sophisticated sonographer. my hidden thesis of the post is that if ultrasound findings are followed in a clinical vacuum and followed without really understanding the physiology [which can explain clinico-sonographic dissociation – like the patient in my fictitious case]… disappointment awaits.
I think the issue of POCUS in resuscitation is somewhat analogous to Prometheus’s gift of fire to humanity.
Jon has quite aptly pointed out that if POCUS (particularly a single POCUS supplied data point such as IVC diameter), if used in isolation, without clinical context, and without comprehensive information, is not much better than using a single data point such as CVP to make complex clinical decisions. Multiple factors influence the behavior of the IVC, just as they do with the CVP. Being a dynamic entity, the IVC does have some advantages over a static number like the CVP. However, if considered by itself, the IVC POCUS evaluation will only result in the same pitfalls as using the CVP as a guide to fluid management. If POCUS is applied in such a blunt manner, we are doomed to repeat our previous folly of using the CVP as a guide to fluid resuscitation. I hope I am in the ball park of the core of Jon’s point here, if not as very eloquently stated by him.
Phil is advocating a more nuanced and sophisticated approach to POCUS than what the SHOC-ED trial investigators used to guide management in their study. Most shocked patients presenting to the ED (“Emerge!”) come with a phenotype of distributive shock. Indeed, these were the majority of the patients in the SHOC-ED trial. Any experienced clinician will recognize this syndrome virtually every time, with no more than an “eyeball and Gestalt” assessment from across the room and a set of vital signs. Current dogma is that this syndrome ought to be treated with 30 cc/kg of crystalloids and then to add a vasopressor if the patient’s blood pressure is still low. Given this, there couldn’t have been much difference as to how patients were managed in either group in this study. I however, disagree with this aggressive crystalloid administration approach, as I’m sure many readers of Phil’s blog do as well. What I gather Phil is saying here is, as he insightfully stated in the past, “IVC never lies, it’s just not telling you the whole story.” A complete POCUS gives us (OK, well almost) the whole story. The caveat here is you must know a whole lot about POCUS. Thus the Prometheus analogy. A little information is a child playing with fire.
Someone new to POCUS, with only a novice’s understanding of what an IVC POCUS evaluation means, will probably make the correct assessment of a patient’s fluid status about 60-70% of the time. This probably is only slightly better than an experienced clinician’s non-POCUS judgement. Hardly enough to translate into any meaningful clinical outcome in a trial without a ridiculously large sample size to find a pretty small benefit. But POCUS potentially offers so much more information. LV and RV systolic function, LV and RV diastolic function, SV, CO, SVR, PVR, RAP/CVP, sPAP/mPAP/dPAP, LVEDP/LAP/PAOP, valvular pathology, tamponade, fluid responsiveness (for what ever that’s worth!), RV/LV interactions (both in series and in parallel), EVLW, insight into pulmonary vascular permeability, renal resistive index/renal venous congestion, portal hypertension/congestion, gut flow resistance, and on and on. Most of this information can be more or less determined in less time that it takes to put in a central line in order to get the damned CVP (actually, I do like to know what my CVP is, for what it’s worth). The more data points you are able to collect with increased POCUS skills and experience, the more grasp you have as to what is going on with your patient and the right way to treat them. I would argue that given the information attainable with advanced POCUS skills, POCUS is a no-brainer that will enormously improve not only individual patient outcomes, but effect populations at large, if only the general hospital based practitioner can attain a more than introductory understanding of POCUS.
So, I guess the question is, “how much training is enough training?” I don’t know. Inevitably, POCUS knowledge will incur a bit of the Dunning-Kruger effect as pointed out by Jon’s example of an IVC POCUS fail. But reading Jon’s clinical case example, from the get go, I found myself asking questions that would change may management one way or another with additional information that I could get quickly and easily with additional POCUS interrogation of the patient. Jon pointed this out himself by revealing that the patient has pulmonary hypertension as manifested by the tricuspid regurgitation upon auscultation of the heart. With POCUS, I don’t need to guess what a heart murmur is or how bad it is or even if it is relevant to my patient in this case for that matter. POCUS can tell me it’s TR and it tells me what the sPAP/mPAP/dPAP and PVR is if I care to find out. So if this level of information can be gleaned, for me, no one can argue that POCUS has no merit. But, I’ve spent a lot of time striving to be good at this, just as probably a lot of people reading this have done as well. What about newbies?
Consider: At my main hospital, for a variety of sensible reasons I won’t get into, we decided to train a group of nurses in POCUS in order to evaluate septic patients. They achieve basic training in POCUS and are very competent sonographers with regard to IVC, gross LV and RV function, and pulmonary edema. They are a small group of very intelligent, skillful nurses that are excited to learn all they can. We had them evaluate every septic patient that presented to our hospital, do a POCUS exam, and discuss the findings with a physician. We established some very basic resuscitation endpoints largely based on POCUS findings applied to each individual patient and their POCUS exam. Our severe sepsis/septic shock mortality rates dropped from 35-38% to 8-10% with this program. Our hospital plans to publish this data officially soon for public analysis, but it did make a difference in our experience. That said, my nurses do frequently show me cases where I notice some small detail on their POCUS exam that propmts an additional investigation that alters the plan in management. Also, some of my very competent POCUS savvy residents make errors because they don’t have enough knowledge yet. I’m sure I can make these errors too at times as well, although hopefully less and less so with time.
Here’s my point: Heed Jon’s admonition to look at the big picture and not rely on isolated data points. Be inspired by Phil’s passion for the potential of a good POCUS evaluation. If you only get your toes wet with POCUS, you are playing with forbidden fire. But if you care to look into it further, POCUS opens up worlds to you. By all means, learn all you can about POCUS. Recognize that if you are new to POCUS techniques, there are improtant caveats to each finding, and physiology that needs to be considered with a comprehensive view, some of it may be strictly non-POCUS related information as well. Your patient is unique and only a careful comprehensive consideration of what’s going on with your patient will guide the best approach to your management of their illness. I don’t think SHOC-ED or any other trial for that matter can address the nuances of good individualized patient management. That is up to you.
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