SVV and passive leg raise

[VentdependenT]

I can honestly say that I've only done a passive leg raise ONCE and that was looking at IVC variation on a spontaneously breathing non-intubated patient.

Do you guys do this? How does it help you out.

I check SVV and if variable then give a bolus and follow SVV and CI afterwards.

I also RARELY see people check SVV appropriately. I turn up TV to 10CC per kg and drop RR to 12 if I can to assess SVV more accurately. You all do this?

I also see FloTrac monitors being used on NON-Intubated patients for SVV. Whats up with that?

Recently I've been looking at brachial/arotic arch/ femoral artery systolic doppler variation as it can be use in spontaneously breathing patients. Its quite variable though and as of you I dont rely on it.

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[Hernandez]

I can honestly say that I've only done a passive leg raise ONCE and that was looking at IVC variation on a spontaneously breathing non-intubated patient.

Do you guys do this? How does it help you out.
.

SVV no....PPV yes.

The problem is SVV is averaged over 20 seconds or so depending on the device, so how is the machine going to know when you start the leg raise? That being said, it's not easy to do it with PPV, you need 2 people 1 for the leg raise and 1 to man the printer and mark when you raise, and not all monitors include the vent pressure tracings to help match up pulse with breath.

I also RARELY see people check SVV appropriately. I turn up TV to 10CC per kg and drop RR to 12 if I can to assess SVV more accurately. You all do this?

You don't have to, but the best study to date was mischard's which followed that methodology.

So the real question you should ask is WHY does Michard use such high tidal volumes? Much of it is to over come compliance issues in patients. I'm having a hrs time putting my hand on the paper by Michard at the moment, but the short of it is that he percentage of pressure transmitted to the pleural space (what we really care about) is related to the compliance. So in a relatively healthy lung with a compliance of 60, you get much but lets take a stiff lung with a compliance of 20 then limit the tidal plume by limiting pressure and you don't get nearly as large swing to create a differential to give a useful PPV.

I also see FloTrac monitors being used on NON-Intubated patients for SVV. Whats up with that?

In THEORY, you can use it, but for many of the same reasons as above, I think you're better off using PPV (it is more accurate anyways) and instructing the pt to take a deep breath and hold then exhale and hold.

I don't have all my references handy on my ipad, but if you want he references just. Let me know and I'll get them to you.

 

[VentdependenT]

THANKS!

Awsome stuff man.

When you do PPV are you following the systolic change on doppler or what? Whats your "cutoff" %variation for predicting volume responsiveness. From what I read using doppler variation in peak, its 8% for common femoral and 16% for brachial.

What do you do?

 

[Hernandez]

I follow michard's 13% as a cut off.

 

[sluggs]

Call me crazy or oversimplified, but try this approach:
Check a BP (cuff, a-line, whatever you are using)
Bolus 500 ml NS or LR FAST on a Pressure Bag (over 10-15 min)
Recheck BP
If pulse pressure improves by > 12%, the patient is fluid responsive. Repeat until patient is no longer fluid responsive, and if still hypotensive start a pressor.
This is a valid and dynamic measure of fluid responsiveness, is simple, and workd on everybody (even amputees-- this is not a joke, and you should remember that even though 'leg raise' is validated, it returns variable amounts of fluid depending of patient variables).
Anybody do this?

 

[Hernandez]

If pulse pressure improves by > 12%, the patient is fluid responsive.

Where'd you come up with this number?

 

[VentdependenT]

I follow michard's 13% as a cut off.

For SVV yes. You use same cutoff for PPV?

 

[jdh71]

Where'd you come up with this number?

I think 12% difference is that magic number where "statistically" the difference from where you started and where you end up, if it's a 12% difference, it is 95% likely that the change was the result of the intervention that occurred in the meantime. Like with bronchodilator challenges for PFTs.

 

[Hernandez]

For SVV yes. You use same cutoff for PPV?

Michard was who came up with 13% and he studies PPV.