Passive leg raising-induced changes in mean radial artery pressure can be used to assess preload dependence

Introduction

We evaluated whether changes in, routinely measured, mean radial artery pressure (MAP) due to passive leg raising (PLR) can be used to assess preload dependence in nonspontaneous breathing patients. We therefore compared the changes in cardiac output (CO) with changes in MAP, pulse pressure (PP) and systolic pressure (SP) as well as the stroke volume variation (SVV) before PLR.

Methods

In this prospective, intervention and response study, 30° PLR of both legs was performed in 20 supine patients receiving mechanical ventilation after elective cardiothoracic surgery. The thermodilution cardiac output (COtd), heart rate, central venous pressure (CVP), MAP, PP, SP and SVV measurements were performed before, during and after PLR.

Results

The COtd, MAP, CVP, PP and SP increased after PLR. No change in heart rate and systemic vascular resistance was observed. We found a significant correlation between PLR-induced changes in COtd versus SVV during baseline (slope = 0.902, P = 0.003), changes in MAP (slope = 0.499, P = 0.003), PP (slope = 0.190, P = 0.024) and SP (slope = 0.276, P = 0.021). Changes in CVP were not correlated to changes in COtd. The area under the receiver operating curves was larger than 0.7 but not different for MAP, PP, SP and SVV.

Conclusion

Not only baseline SVV but also PLR-induced changes in MAP, PP and SP are reliable parameters to assess preload dependence in cardiac surgery patients. In the clinical setting we prefer the MAP approach, based on simplicity, availability and robustness.