I have covered many things resuscitation and fluid responsiveness thus far on this page. Fluid responsiveness has been defined as a patient given either a certain amount of fluid or a passive leg raise to assess how that will increase the cardiac output/index or stroke volume. This post will be about stroke volume variation (SVV) and how it predicts fluid responsiveness. The objective is to not drown our patients with too much fluid. I have covered many things Resuscitation and Fluid Responsiveness category of my page here. There’s also a full blog post on Fluid Resuscitation HERE that I’ve been working on.

What is Stroke Volume Variation (SVV)?

Stroke volume variation is a measure of the change in stroke volume (SV) that occurs in respiration in patients. This change is induced by the heart lung interaction. It is measured from the stroke volume component of the arterial waveforms and calculated. More on the calculation shortly.

Why is Stroke Volume Variation important?

SVV is a dynamic form of assessing for volume responsiveness in patients who are on mechanical ventilation and need resuscitation with IV fluids. It predicts the ability for there to be a change in the stroke volume with a fluid bolus. The major downside to this methodology is that you need some sort of device such as pulse contour analysis or bioreactance to sort this out. You’ll need an arterial line in the case of pulse contour analysis (except for one particular device to my knowledge). I am quite familiar with one of these devices although I am not going to divulge any further information for sake of possible bias. It is also important to reemphasize that patients need to be on mechanical ventilation.

What is the Stroke Volume Variation (SVV) Equation?

SVV= (SVmax – SVmin) / SVmean

SVV is calculated as the difference between the stroke volume on inspiration and expiration in the respiratory cycle. Fortunately, we don’t have to do it by hand these days. The machine/device does it for us and we get a pretty number.

What Stroke Volume Variation (SVV) is considered “normal”?

Depending on the literature, a patient who is predicted to be volume responsive will have an SVV>13% in most literature, but some will say >10%. In my practice, I use the former. The normal range of stroke volume variation is <13%. One could interpret the number that if it’s over 13%, they could potentially benefit from a fluid bolus.

Does SVV Predict Fluid Responsiveness?

There was a meta-analysis that looked at 568 patient in 23 different studies using a variety of different devices. The correlation coefficient to fluid responsiveness was 0.718 which means a “highly positive correlation”. The AUC of using SVV for fluid responsiveness is 0.84. 0.8-0.9 is considered “excellent”. It’s not all sunshine and roses, though. I know we’re rusty on our stats.

How is SVV measured?

There are various ways to assess the SVV:

• Arterial waveform analysis
• Pulse Contour Analysis
• Esophageal doppler
• Echocardiography (both TTE and TEE)

I have personally only used pulse-contour analysis technologies to obtain this measurement.

When was SVV first described in the literature?

The first study to describe stroke volume variation (SVV) that I was able to find was back in in 2002. That article was titled “Stroke volume variations for assessment of cardiac responsiveness to volume loading in mechanically ventilated patients after cardiac surgery“. Here, they found that SVV was useful in cardiac surgery patients . It uses included the ability to “predict and continuously monitor effects of volume administered as part of their hemodynamic management”.

Limitations of Stroke Volume Variation (SVV):

– needs to be on mechanical ventilation
– no cardiac arrhythmias
– tidal volume needs to be >8cc/kg of ideal body weight
– you need a fancy machine
– most devices need an arterial line
Part of the issue is that clinicians are quick to forget these limitations.

Stroke Volume Variation in Patients on Low Tidal Volumes

Stroke Volume Variation, also known as SVV, is a method to assess fluid responsiveness in critically ill patients.
Criteria to obtain an accurate stroke volume variation include that the patient needs to be on the vent and not spontaneously breathing.
They cannot have any cardiac arrhythmias.
They need sometimes need arterial line and always need a fancy device to measure the stroke volume variation.
If you have all your ducks in a row, using SVV is considered to be excellent with an AUC of 0.84 based on a previous systematic review and meta-analysis.
This is using a threshold of >13% to be fluid responsive.
A caveat that I thought was of utmost importance was that the patients should be set at a tidal volume at, or greater than 8cc/kg.
I recently found a paper by Alvarado et al. that looked at numerous hemodynamic parameters to assess fluid responsiveness.
Using a threshold of 12, the authors found an AUC of 0.9 for patients in patients on low tidal volume.
Does this mean that we can throw out the tidal volume parameter?
What do you think in the comments.

Does SVV work on patients who are spontaneous breathing?

Stroke Volume Variation doesn’t work in patients who are spontaneously breathing. I have seen clinicians who are well respected where they’ve said that it works “to trend” but I am not a fan of shortcuts. The AUC in those patients is 0.53 per the linked Zhang paper. Perner et al. found that this does not work with an AUROC of only 0.51. That means that a coin flip is as accurate as SVV in determining fluid responsiveness.

Putting it all together

All in all, it’s another tool in the tool belt. We need as many as we can. I personally would prefer to have this value showing up on a screen over numerous other parameters that require me to be at the bedside on x minute intervals.

If you want to learn about pulse pressure variation, CLICK HERE.

Citations:

Reuter DA, Felbinger TW, Schmidt C, Kilger E, Goedje O, Lamm P, Goetz AE. Stroke volume variations for assessment of cardiac responsiveness to volume loading in mechanically ventilated patients after cardiac surgery. Intensive Care Med. 2002 Apr;28(4):392-8. doi: 10.1007/s00134-002-1211-z. Epub 2002 Mar 20. PMID: 11967591.
Link to NOT FREE Article

Zhang Z, Lu B, Sheng X, Jin N. Accuracy of stroke volume variation in predicting fluid responsiveness: a systematic review and meta-analysis. J Anesth. 2011 Dec;25(6):904-16. doi: 10.1007/s00540-011-1217-1. Epub 2011 Sep 4. PMID: 21892779.
Link to Abstract

Perner A, Faber T. Stroke volume variation does not predict fluid responsiveness in patients with septic shock on pressure support ventilation. Acta Anaesthesiol Scand. 2006 Oct;50(9):1068-73. doi: 10.1111/j.1399-6576.2006.01120.x. Epub 2006 Aug 25. PMID: 16939480.
Link to Article
Link to FULL FREE PDF

Vignon P, Repessé X, Bégot E, Léger J, Jacob C, Bouferrache K, Slama M, Prat G, Vieillard-Baron A. Comparison of Echocardiographic Indices Used to Predict Fluid Responsiveness in Ventilated Patients. Am J Respir Crit Care Med. 2017 Apr 15;195(8):1022-1032. doi: 10.1164/rccm.201604-0844OC. PMID: 27653798.
Link to Article
Link to FULL FREE PDF

Hofer CK, Cannesson M. Monitoring fluid responsiveness. Acta Anaesthesiol Taiwan. 2011 Jun;49(2):59-65. doi: 10.1016/j.aat.2011.05.001. Epub 2011 Jun 24. PMID: 21729812.
Link to Article
Link to FULL FREE PDF

Alvarado Sánchez JI, Caicedo Ruiz JD, Diaztagle Fernández JJ, Amaya Zuñiga WF, Ospina-Tascón GA, Cruz Martínez LE. Predictors of fluid responsiveness in critically ill patients mechanically ventilated at low tidal volumes: systematic review and meta-analysis. Ann Intensive Care. 2021 Feb 8;11(1):28. doi: 10.1186/s13613-021-00817-5. PMID: 33555488; PMCID: PMC7870741.
Link to Article
Link to FULL FREE PDF

Other Resources:
Jon-Emile Kenny, MD wrote a great review. Always love his work. SVV.
Alex Yartsev wrote a great review on his page “Deranged Physiology”

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