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• The passive leg rising test can be used to asses whether the patient is volume responsive or not.

• It is based on the frank starling curve.

• Lifting the legs passively from horizontal position induces a gravitational transfer of blood from the lower limbs towards intrathoracic compartment resulting in increased pulmonary artery occlusion pressure and LV ejection time, the volume of blood transferred to the heart is sufficient to increase the left cardiac preload and thus challenge Frank -Starling Curve.

• The change in aortic blood flow during a 45 degree leg elevation was shown to predict the changes in aortic blood flow produced by a 500ml fluid challenge even in patients with cardiac arrythmias and or spontaneous ventilator trigger.

How to perform PLR ?

• A simple way to perform PLR is to transfer the patient from semirecumbent posture to the passive leg rising position (elevate the limb by 45degrees) by using the automatic motion of bed.

• Maximal hemodynamic effect occurs within first minute. This stresses the need for real time monitoring of cardiac output or stroke volume.

• There are several invasive and non invasive method to asses the stroke volume. These includes pulse contour analysis , transpulmonary thermodiltuion & biorectance method.

• PiCCO system and Flo Trac- Vigileo calculated SV from pulse contour analysis.

• An increase in SV by more than 10% in response to PLR is predictive of volume responsiveness in mechanically ventilated patients with spontaneous breathing activity.

VIDEO :Click on this link for an excellent video on SVV and PLR from edwards life science.



Other Techniques

• PLR test can be assessed passively by bioreactance technique using NICOM. NICOM comprises high frequency sine wave generator and four dual electrode used to establish electrical contact with the body, and measures cardiac output. Studies have shown that it can accurately predict fluid responsiveness in PLR test.

• The response of descending aortic blood flow to PLR (echo, esophageal doppler) and femoral artery flow (arterial doppler) to PLR have demonstrated to be helpful in patients with spontaneous breathing activity but they are subjective and cannot be used for continuous monitoring.

• Dynamic changes in plethysmographic waveform have been demonstrated to be predictive of volume responsiveness in ventilated patients but it poorly predictive of volume responsiveness in spontaneously breathing persons after a PLR challenge; because pulse pressure is not sufficiently enough for detecting stroke volume.

Advantage

• It can be done in patients with spontaneous breathing, arrythmia.

• Effect of the challenge is reversible.

Disadvantage

• Intrabdominal pressure > 16 mmHg impairs venous return and reduces the ability of PLR to detect fluid responsiveness.

• Requires special instruments for continuous monitoring of pulse contour.

Updated on 12/1/2015

Reference

• Hemodynamic parameters to guide fluid therapy ; Annals of intensive care