Podcast 64 – Fluid Responsiveness with Dr. Paul Marik

Today I had the pleasure to interview Dr. Paul Marik, Professor and Division Chief of Pulmonary Critical Care at Eastern Virginia Medical Center. We got to speak on the topic of fluid responsiveness–one of the toughest questions in critical care.

Fluid Responsiveness

The definition we are using for fluid responsiveness is an increase of stroke volume of 10-15% after the patient receives 500 ml of crystalloid over 10-15 minutes

Dr. Marik’s Path through the Morass

this is a modification of the algorithm from Dr. Marik’s upcoming paper

* if using passive leg raise, give a 500 ml bolus if the response is positive

What is Passive Leg Raising?

For a brief period of time, a bolus of fluid is sent to the heart, allowing you to test fluid responsiveness without doing anything permanent to the patient’s fluid status.

What is the Monitor that Dr. Marik mentioned?

The NICOM Monitor by Cheetah Med uses bio-reactance to yield cardiac output/stroke volume non-invasively. I have been trialing the monitor and have been very impressed so far. It is inexpensive and correlates with my echocardiograms.

Articles of Interest

Neither Dr. Marik nor I have any Conflicts of Interest!

Update 6-10-12

Here is an amazing review article by Dr. Marik on this topic

and Now to the Podcast…

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  1. says

    I noticed the technology used in the NICOM product runs a small current through the patient at radio frequencies (not sure if it is low-frequency or high-frequency). Does this interfere with the surface ECGs or do the standard monitor-mode filters work fine?

  2. Minh Le Cong says

    Thanks Scott and Dr Marik
    Profound stuff! Keep it up. My service looked into one of these non invasive CO monitors using doppler USS. a few years ago and nothing ever came of it as the evidence at the time was not so convincing. It seems things have matured. prehospital CO measurement…now thats an exciting concept!will chase this up again with my retrieval colleagues!

    • Daniel says

      Going back to transport medicine and going to work in fixe wing and with clinic with low budget and not much technology, what will be my best approach to assess my patient? Been a nurse I may not have access to arterial line unless someone can place them.

  3. says

    Hi Scott. Sounds like there has been a lot of movement in this area in just the last 12 months or so.
    I have been trialling the arterial line based SVV CO monitor and found it has limitations as discussed in the talk with Dr Marik
    Probably the single biggest limitation is the reliance on the staff to run the machine / calibrate, interpret and “trust” the numbers. There is a lot of fiddle and training required for the device we are using at the moment – and it does rely on a patient being ventilated – so only the super sick in Broome.

    For me, the need to stick an A-line into somebody where you may or may not great data out is tough, and my colleagues are not convinced either – so a completley non-invasive device that costs nothing in terms of harm to the patient is a winner in my shop. I think it will be the next device I trial – it will be nice to have a device you can use on the medium-sick patients, to learn the ropes and get a feel – it always seems unfair to “play and learn” on a patient who is really in trouble. With limited resources in terms of manpower – fiddling can be doing harm to the patient!

    Will have to get me one of those!

  4. Shaun says

    Hi Casey,

    What monitors do you guys run?

    The Phillips MP line does PPV (aka SVV) out of the box (at least the MP50, 70 and 90’s I play with, not sure about the MP30), so if you have a medium sick patient who you don’t feel like putting a Vigeleo on (I assume it’s a Vigeleo), you can set it up and it spits out a number at you, no fiddling with another machine or otherwise interrupting your workflow; enable it, wait ~30 seconds, and get a number.

    I use PiCCO and Vigeleo a fair bit, but it can be tough convincing other people that they improve outcomes given there doesn’t appear to be much evidence at all when it comes to ICU patients.

    The NICOM monitor looks very interesting, although I think it could be tough to convince people it gives real numbers; a lot of people still scoff at the numbers that a PiCCO thermodilution gives you.

    (I swear I don’t represent any of these companies, I just love me some technology!)


  5. Mike Jasumback says

    Got a bit worried when he started talking noninvasive! We trialled a bioimpedance device about 7-8 years ago and were way less than impressed. I’ve often wondered why more people don’t use the simplest tests, 500cc bolus or passive leg raise. Dr. Marik shows remarkable common sense.

  6. Simon says

    Scott, thank you for this amazing blog. Besides tons of useful information it’s a great source of inspiration.

    Just want to ask what you think of dr Lichtenstein’s protocol where you give fluid till you get the “wet” pattern on lung ultrasound (predominant B-lines)? It’s extremely simple so nice in the ED/non-ICU ward, and you get to see what actually happens in the organ most sensitive to fluid overload. Even SV must be a surrogate parameter in a sense?

  7. anthony says

    in performing the passive leg raise—how long do you wait before rechecking the blood pressure? what are you using as your stroke volume surrogate?–systolic, diastolic, or MAP? I assume we are looking at a greater than 10% increase as being indicative of “fluid responsive”. This seems imprecise without an A-line but you say simple non-invasive BP measurement can work?

    • says

      Intermittent blood pressure will not work. For an a-line I think a 10% increase in MAP or SBP is a reasonable positive. But if negative, it doesn’t mean the patient is not fluid responsive.

  8. says

    Scott –

    I appreciate the perspective of Dr. Marik, and it was an interesting discussion. It was somewhat frustrating to hear, though, to hear the empiric data for septic shock dismissed out of hand.

    I would tend to agree about the accuracy of CVP as an isolated measurement of fluid responsiveness, no argument there. However, whatever the limitations of the Rivers trial, it gave us actual outcomes, an NNT for mortality. You can’t ignore the fact that it did so, in part, by using the CVP to guide therapy.

    Sure, there may have been some clinicians who applied the results of EGDT in a rote, unthinking fashion – “6 liters in the first 6 hours” – but it seems like Dr. Marik used that characterization to invalidate the application of the study’s results, setting up a “straw-man” argument.

    Is there any comparable outcomes-based research using the NICCOM or similar) devices?

    Thanks for the podcast!

    • says

      Brooks, Thanks for the comment. I can’t say I agree with you. One thing the EGDT trial did not show at all is any value to CVP per se. Both groups got CVP monitoring and both groups had the same CVP goal.

      I believe Dr. Marik’s comment re: empiric fluid admin was less a commentary on Rivers’ trial than the ongoing PROCESS trial in which empiric fluid admin without a marker is considered a good idea.

  9. Carlos F Crespo, M.D. says

    Dr. Weingart, I want to congratulate you for this podcast, it is excelent, for me, the best of the best. I work in Laredo, Tx Doctors Hospital ER and I use a lot of your concepts to take care of my patients. Again congratulations and I hope you
    keep on with this cast.
    Best wishes
    Carlos F Crespo, MD

  10. BAF says

    Fantastic podcast! I’ve been waiting a while for this one. I have a couple of quick questions though. First, is there any data out there on whether sonographic parameters like IVC collapse or LV diastolic function (like the ultrasound podcast guys suggest) correlate w/ fluid responsiveness vs just static measures like CVP OR PAOP?

    Second, and this is just a random thought I had, but what about using a continuous ScVO2 monitor in lieu of the SV monitor in the algorithm above to see if DO2 is increased w/ the fluid challenge?


    • says

      IVC with mech vent has shown fluid responsiveness; spont resp–nope.

      ScvO2 and SvO2 has been used for this purpose (and to decide who needs blood transfusions as well). It is a bit downstream though, and doesn’t measure regional improvements in perfusion.

  11. Lance C. Peeples says

    Does anyone have any experience with the NICOM in the pediatric population? Are there any studies supporting the use of this monitor in pediatrics?

  12. Michael Ashbolt says

    Hi Scott, Loved this podcast. Totally agree with the best measure being actually giving a volume challenge via fluid or passive leg raise and evaluating the results. However, given the infrequency of CO monitoring in my ICU – I do also find myself using a gross assessment of PPV or Systolic pressure variation and IVC distensibility as well as the chart etc in my assessment of whether a patient will be fluid responsive. My question is:

    Given that we have established that there is poor correlation between CVP and fluid responsiveness, what is the physiological rationale behind why IVC distensibility works. I understand that it is a dynamic test however, surely it is simply proportional to the relationship between the airway driving pressure (Pinsp-PEEP) and CVP. As such it does not really represent the preload to the LV and it is affected by all the same variables as CVP such as RV dysfunction, changes in pulmonary vascular resistance etc that occur in critical illness.

    Or am I missing something. Perhaps the original studies were in a healthier population with good lungs and good RV function. Any help with thinking this through would be great – as I really think IVC ultrasound is a neat test but can’t get past the above theoretical problems.

    Cheers, Mike
    ED/ICU registrar Australia

    • says


      Assume we are talking about tubed pts on mech vent. In this case, IVC is really resp-dynamic CVP which nobody has looked at and probably would be quite good as opposed to static CVP. What we can say is that we have a bunch of studies on IVC in thsi group and it seems to towk nicely.

  13. Paul says

    How can the CVP be a the devil and the IVC be wonderful. They are looking at the same vessels! I know CVP is pressure and IVC is volume. Is it possible to have a high CVP with a full collapse and possitve IVC exam? Please explain!

    • says

      Paul, In this case, I assume we are talking spont vent pts. Static CVP may be the devil for fluid responsiveness, but not tolerance. Dynamic CVP may be that much better. IVC in the way I advocate is dynamic and used for tolerance; for this it is pretty good.

  14. Fletch says

    Is there a pocket sized US machine that is a reasonable cost? It would be great to see an adapter for a phone of tablet device to allow one to reasonably assess fluid responsiveness ASAP especially in HEMS. Or even better perform a FAST in the field to discover what you don’t know yet but will discover as VS decrease.

    • says

      I was not yet impressed with the ones I have found. Write the ultrasoundpodcast.com guys on their site as they have access to the cutting edge devices.

  15. David Levy says

    Study done at a hospital I worked out employing non-invasive monitoring:
    Dunham CM, Chirichella TJ, Gruber BS, et al. Emergency department noninvasive (NICOM) cardiac outputs are associated with trauma activation, patient injury severity and host conditions and mortality. J Trauma Acute Care Surg. 2012; 73(2): 479-485
    BACKGROUND: Anoninvasive cardiac output (CO) monitor (NICOM), using Bioreactance technology, has been validated in several nontrauma patient studies. We hypothesized that NICOM CO would have more significant associations with clinical conditions than would systolic blood pressure (sBP).

    METHODS: This is a prospective observational study of consecutive trauma activation patients during the first 10 to 60 minutes after emergency department arrival.

    RESULTS: Analysis includes 270 consecutive trauma activation patients with 1,568 observations. CO was decreased (p ? 0.002) with major blood loss, hypotension, red blood cell transfusion, Injury Severity Score (ISS) higher than 20, low PetCO?, abnormal pupils, elderly, preexisting conditions, low body surface area level, females, hypothermia, and death. CO was increased (p < 0.0001) with base deficit, ethanol positivity, and illicit drug positivity. The sBP was decreased (p ? 0.0005) with major blood loss, red blood cell transfusion, low PetCO?, low body surface area level, and illicit drug positivity. The sBP was increased (p e 0.01) with ISS higher than 20, elderly, and preexisting conditions. Total significant condition associations were CO 83% (15 of 18 patients) and sBP 47% (8 of 17 patients; p = 0.03). In hypotensive patients, CO was lower with major blood loss (3.3 ± 2.1 L/ min) than without (6.0 ± 2.2 L/min; p < 0.0001). Of survivors with ISS 15 or higher, NICOM patients experienced a shorter hospital length of stay (10.5 days) when compared with 2009 and 2010 patients (14.0 days; p = 0.03).

    CONCLUSION: The multiple associations of CO with patient conditions imply that NICOM provides an objective and clinically valid, relevant, and discriminate measure of cardiac function in acutely injured trauma activation patients. NICOM use may be associated with a shorter length of stay in surviving patients with complex injuries.


  16. Michelle Lowe says

    Hi Scott. Just referenced this podcast with Sepsis Alliance for Trinity Health Care. Thanks so much


  1. Lecture for September 4th, 2013: Should anyone use CVP anymore? A consideration of the data | It's All About the Evidence says:

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