SVV, PPV and SOS

Many clinical studies have demonstrated that the arterial pulse pressure variation (PPV) and the stroke volume variation (SVV) are accurate predictors of fluid responsiveness.



A recent meta-analysis showed that the average sensitivity and specificity of these two parameters is 85%, which is indeed not perfect, but quite impressive when compared with all other clinical indicators.


However, these dynamic parameters have limitations precluding their use in several clinical situations.

The main limitations to the use of dynamic parameters in surgical patients have been recently summarized as ‘SOS’.


The first ‘S’ stands for small tidal volume and spontaneous breathing activity; the ‘O’ stands for open chest.



In these conditions, changes in intrathoracic pressure are usually too small to induce significant changes in venous return. As a result, a false-negative may be observed, that is a small PPV or SVV in fluid responders. Several clinical studies have confirmed that the predictive value of PPV and SVV is decreased when

• patients are breathing spontaneously,
• when they are mechanically ventilated with a tidal volume ,7–8 ml kg
• when the pericardium and the chest are open.

The second ‘S’ stands for sustained cardiac arrhythmias. In this setting, PPV and SVV reflect altered cardiacfilling times rather than the effects of mechanical ventilation and then cannot be used to predict fluid responsiveness.

Finally, questions remain regarding the usefulness of dynamic parameters in other clinical situations such as laparoscopic procedures, where they may still be valuable but with different cut-off values.

In conclusion, there are  that limitations to the use of dynamic parameters.

However, this  should not discourage clinicians to use dynamic parameters when they can, and alternative solutions when necessary. Indeed, rational and individualized perioperative fluid strategies are

key to decrease the human and economic burden of postoperative complications.

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3. Michard F. Volume management using dynamic parameters: the good, the bad, and the ugly. Chest 2005; 128: 1902–3
4.  Lansdorp B, Lemson J, van Putten MJAM, et al. Dynamic indices do not predict volume responsiveness in routine clinical practice. Br J Anaesth 2012; 108: 395–401
5. Michard F. Stroke volume variation: from applied physiology to improved outcomes. Crit Care Med 2011; 39: 402–3