In Greek mythology, Prometheus (/prəˈmiːθiːəs/; Greek: Προμηθεύς, pronounced [promɛːtʰeús], meaning “forethought”) is a Titan, culture hero, and trickster figure who is credited with the creation of man from clay, and who defies the gods by stealing fire and giving it to humanity, an act that enabled progress and civilization. Prometheus is known for his intelligence and as a champion of mankind.
So, fresh from reading Jon’s post, I felt I had to add a bit of nuance in my previous post to what I feared some might extract as a take-home message, even if in fact, we are not that differing in opinion at all – which Jon expressed here:
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.
nice analogy – i think Korbin’s response is appropriate and i look forward to speaking alongside him in May. as i chew on the SHOC-ED a little and try to distill my concerns – i think what it boils down to is this: it’s less about playing with fire – i think – and more about how this fire is brought to the community as a whole. my post on pulmccm was more of a warning to the early adopters [like us] who are planning these trials. imagine 40 years ago:
-the flotation PAC is introduced, a small group of clinical physiologists use it thoughtfully, understand the caveats, the problems of data acquisition, interpretation, implementation, the problems with heart-lung interactions, intra-thoracic pressure, etc.
-these early adopters present their results to the community as a whole
-the physiology of the PAC is simplified
-the numbers from the PAC are introduced into algorithms and protocols and **widely** adopted into clinical practice
-the PAC is studied based on the above and found to make no difference in patient outcome.
-in 2010 a venerable intensivist suggests floating a PAC in a complicated patient and the fellow on rounds chuckles and states that their is ‘no evidence of benefit’
does this sound eerily familiar? is our present rhyming with the past? if the planners of POCUS trials are not careful, i promise you that the same will happen but insert any monitoring tool into the place of PAC. i can very easily visualize a fellow on rounds in the year 2030 scoffing at the idea of PoCUS because trials [SHOC-ED, and future trials x, y and z] showed no difference in patient outcome. is it because PoCUS is unhelpful or is it because the way it was introduced and studied was unhelpful? and the three of us will sound like the defenders of the PAC from 30 years ago: “PoCUS isn’t being used correctly, it’s over-simplified, it works in my hands, etc. etc.”
it’s not PoCUS that’s unhelpful, it’s how we’re implementing it – and i was most depressed when the authors of SHOC-ED appeared to stumble upon this only in the discussion of their paper – like you mentioned phil. imprecise protocols will result in equally imprecise data and the result will be nebulous trial outcomes. we should all be worried.
Excellent points Jon. The PAC example is very relevant, as on more than one occasion, I’ve had the argument put to me by some colleagues that essentially how I’m applying POCUS is really no different than the information gleaned from the PAC, and “that’s been shown to not be helpful to outcomes” etc. So, therefore, why do I bother?
Then again, I’ve seen a fair amount of phenylephrine being thrown at hypotensive cardiogenic shock patients after a 2 liter normal saline bolus didn’t do the trick.
You are absolutely spot on when you point out that seeing the big picture, knowing the physiology, and being aware of the pitfalls of isolated data points is important to making the right decisions in patient care.
Furthermore, I agree that when a clinical trial is done that doesn’t consider some of the nuances of all this, and “shows” that POCUS, or any other diagnostic modality for that matter, doesn’t contribute to better patient outcomes, it probably only serves to marginalize a potentially valuable diagnostic tool to an actually astute intelligent clinician.
I’m not meaning by saying this to bash the good intentions of the SHOC-ED trial. To be fair, it’s really hard to design a trial that can take into account all the permutations that are involved in any individual patient presents with, having their own unique clinical situations, hemodynamic profiles, co-morbidities (both known and undiagnosed), etc. POCUS, PAC, transpulmonary thermodilution, ECG, chest x-ray, CT scans, labs, physical exam–these are all merely tools that guide patient care. Albeit some are way more powerful than others. I can image various amounts of uproar if some of these traditional tools were subjected to clinical trials to prove their utility. The argument, if proven “useless” in a study for the oldest and well accepted tools would always be, “put it in the clinical context, and its value speaks for itself.” For me, I’d happily like to make clinical descisions based on information based on an advanced POCUS exam or PAC, rather than interpreting hepatojugular reflux or a supine chest x-ray.
Any diagnostic test requires that the clinician understand the limitations of that test, and understand that the whole clinical scenario must me taken into account. You’ve hit on that, I think, with your argument. This surely has implications when any technology or test is studied.