SVV , PPV calculations

[anbuitachi]

A lot of people use these in the OR to assess fluid status however i have noticed that people do it differently

For those of you who have a better grasp of this method of assessment of fluid status, when doing Stroke volume variation, how are you measuring the stroke volume?

For those doing pulse pressure variation, based on the papers it seems like it is PPmax-PPmin/PPmean, with >13% variation indicating likely fluid responsiveness. What i often see people do is measuring systolic pressure variation as a difference(Smax-Smin over some seconds), or a percentage(divided by Smean), and applying the 13% to that instead. Can anyone comment on the accuracy of doing it like this? On machines that don't do PPV for you, calculating it out is difficult, and doing SPV is much simpler, but does 13% still apply when doing SPV?

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[Hoya11]

A lot of people use these in the OR to assess fluid status however i have noticed that people do it differently

For those of you who have a better grasp of this method of assessment of fluid status, when doing Stroke volume variation, how are you measuring the stroke volume?

For those doing pulse pressure variation, based on the papers it seems like it is PPmax-PPmin/PPmean, with >13% variation indicating likely fluid responsiveness. What i often see people do is measuring systolic pressure variation as a difference(Smax-Smin over some seconds), or a percentage(divided by Smean), and applying the 13% to that instead. Can anyone comment on the accuracy of doing it like this? On machines that don't do PPV for you, calculating it out is difficult, and doing SPV is much simpler, but does 13% still apply when doing SPV?

You are making a subtle distinction between SPV and PPV.. and does the 13% still apply if its SPV instead. Keep in mind its all an estimation. But I believe the answer to your question is YES. Since the systolic number is going to be changing the most beat to beat, giving the equation most of its significance, I believe the approach you described would be an equally accurate estimation as PPV.

A weird question though because if the machine doesn't have a PPV calculator, Im not using PPV!

 

[deleted697535]

It's all bs! Give em fluid if you want.
Fluid doesn't carry much oxygen last time I checked so who really cares if they're fluid responsive or not.

 

[caligas]

This thread should get interesting...

 

[Psai]

There's fluid tolerance and fluid responsiveness

The only test for fluid responsiveness is a fluid bolus (500ccs leading to an increase in CO). Everything else is academic garbage

 

[Mman]

PPV

<8% suggests they have no need for fluid. 8-13% is equivocal. >13% suggests they are dry. I like PPV because it is directly measured. SVV is calculated from that and the calculation has the potential to introduce error.

 

[Mman]

It's all bs! Give em fluid if you want.
Fluid doesn't carry much oxygen last time I checked so who really cares if they're fluid responsive or not.

I prefer to provide all patients with about 50L of crystalloid just to see if they can handle it

 

[deleted59964]

I prefer to provide all patients with about 50L of crystalloid just to see if they can handle it

You’re doing it wrong.
I give no fluid, just to see if they can handle it.

 

[Consigliere]

I prefer to provide all patients with about 50L of crystalloid just to see if they can handle it

I do the same. Then when they are in the PACU and pissing up a storm and the PACU nurse squawks out a "how much fluid did you give?!" I look them dead in the eye and say "250 mls."

 

[pgg]

There's fluid tolerance and fluid responsiveness

The only test for fluid responsiveness is a fluid bolus (500ccs leading to an increase in CO). Everything else is academic garbage

Not a believer in the passive leg raise test?

 

[deleted697127]

Just apply the principles rationally. If they’re sitting up you can lay them flat, if pressure goes up they’re likely volume responsive. If you place them trendelenberg and pressure improves, the same..Passive leg raise in a surgical population probably hurts.

As for calculating, just watch the pressure for 30 seconds. Take note of the High PP and the low PP. If the difference is >13ish, they’re probably volume responsive. It’s not usually too far off from the calculated value however that is done..also you have an a line, squeeze fluids in for 30 seconds and if pressure improves continue the bolus.

 

[Psai]

Not a believer in the passive leg raise test?

I'm too young to blow out my back by lifting 50 kg of fat legs

The fluid must flow.

 

[AdmiralChz]

Not a believer in the passive leg raise test?

I'm having bad flashbacks to MS-3 year holding up tree trunks during vascular surgery and orthopedics. I still laugh to myself when I see the med student doing it today. Also helpful in those vascular patients as a quick test of fluid responsiveness... although when the pressure tanks and your CVP skyrockets it makes you wish you were anywhere else.

 

[fakin' the funk]

A lot of people use these in the OR to assess fluid status however i have noticed that people do it differently

For those of you who have a better grasp of this method of assessment of fluid status, when doing Stroke volume variation, how are you measuring the stroke volume?

For those doing pulse pressure variation, based on the papers it seems like it is PPmax-PPmin/PPmean, with >13% variation indicating likely fluid responsiveness. What i often see people do is measuring systolic pressure variation as a difference(Smax-Smin over some seconds), or a percentage(divided by Smean), and applying the 13% to that instead. Can anyone comment on the accuracy of doing it like this? On machines that don't do PPV for you, calculating it out is difficult, and doing SPV is much simpler, but does 13% still apply when doing SPV?

PPV = (PPmax - PPmin)/PPmean, cutoff values as described by others, only for TV > 8ml/kg IBW, must be in a regular rhythm, must not be making respiratory efforts, etc, etc. PPV is great and all but really when it's above 15-20% it is already OBVIOUS how dry the patient is. Like when they clamp the cava during liver tx. Low (normal) PPV is a great reminder to not give fluid.

SVV is just PPV but transformed via some propriety estimate of arterial elastance - Vigileo. The PPV, however, is free.

Don't use systolic pressure variation -- not as reliable. Easy to find the literature on this.