Chris Gough Profile picture
16 Sep, 13 tweets, 6 min read
Thank you to everyone who commented and voted on this case - some great debates!

Before I go through assessment of fluid responsiveness in critical care, it's worth saying that it is one component of your overall assessment of the patient. Not to be taken in isolation. [1/12]
One of the key principles here is that the positive pressure delivered into the thorax from the ventilator will affect the venous return to the right heart (with less returning during inspiration).

This leads to variation in IVC and LVOT VTI/V max values.
Some variation is completely normal.

But when patients are hypovolaemic, they are more susceptible to the pressure changes, & the variation will get larger.

In ICU we can also see this as "swing" on an arterial line trace

It is not so simple in a spont breathing patient
In this case, the IVC variation & LVOT VTI variation were within normal limits:

IVC variability:
<15% - not fluid responsive
>20% - fluid responsive

LVOT VTI variation:
<10% - not fluid responsive
>15% - fluid responsive

The middle ground is not clear one way or other.
The other principle here is about the Frank-Starling curve.

In summary, this says that increasing the pre-load (LVEDV), will increase the stroke volume, up to a point. At that point, further increases will have no affect on SV, and may worsen SV.
[5/12] Image
To assess this we can compare the LVOT VTIs before and after a fluid bolus, or a passive leg raise (PLR).

Using a PLR we deliver a fluid bolus to the patient from their lower limb venous pool - essentially sparing them a fluid bolus if they turn out to be non-responsive.
In this case, the response was negligible.

The normal values are:
Increase of <8% - not fluid responsive
>12% - fluid responsive.

With a zone of uncertainty in between

As with IVC and LVOT VTI, there will be a few exceptions where values can be misleading.
So in this case:
- Minimal IVC variation
- Minimal LVOT VTI variation
- No response to a PLR.

We can confidently say he is currently unlikely to be fluid responsive (remember in critical care the patient can change very rapidly).
The other thing I always try to comment on is any signs of volume overload, to try and help give as much useful info as possible:
- Is the patient unlikely to be fluid responsive and look about right?
- Is the patient unlikely to be fluid responsive and look overloaded?
I didn't show you all the the images here, but can tell you:
- The RV has normal dimensions with normal TAPSE and fractional area change.
- The RA is normal size
- The IVS has normal movement, with no bowing into LV.

In essence, no signs of volume overload.
In summary, this patient is unlikely to be fluid responsive, and has no signs of volume overload.

I attach a helpful diagram I use as my prompt for these scenarios.

It's taken from a book I use, but have no conflict of interest with.
[11/12] ImageImage
I hope this has been useful. As always, do let me know your thoughts, and if you agree/disagree with my interpretation.

@nat_echo @cardiacLucy @scrivsy85 @DrDanAugustine @dr_benoy_n_shah @The_echo_lady @Teresa30031988 @iceman_ex @vitormweaverBSE @MedCrisis @paton_maria

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More from @GoughCJ

15 Sep
This is my first critical care echo case tweetorial. I will be discussing the assessment of potential fluid responsiveness in critical care. Case today, answers tomorrow.

Please do give me honest feedback so I can make these useful.
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Here is the PLAX.
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