Changes in stroke volume induced by passive leg raising in spontaneously breathing patients: comparison between echocardiography and Vigileo/FloTrac device

Abstract

Introduction: Passive leg raising (PLR) is a simple reversible maneuver that mimics rapid fluid loading and increases cardiac preload. The effects of this endogenous volume expansion on stroke volume enable the testing of fluid responsiveness with accuracy in spontaneously breathing patients. However, this maneuver requires the determination of stroke volume with a fast-response device, because the hemodynamic changes may be transient. The Vigileo monitor (Vigileo; Flotrac; Edwards Lifesciences, Irvine, CA, USA) analyzes systemic arterial pressure wave and allows continuous stroke volume monitoring. The aims of this study were (i) to compare changes in stroke volume induced by passive leg raising measured with the Vigileo device and with transthoracic echocardiography and (ii) to compare their ability to predict fluid responsiveness.

Methods: Thirty-four patients with spontaneous breathing activity and considered for volume expansion were included. Measurements of stroke volume were obtained with transthoracic echocardiography (SV-TTE) and with the Vigileo (SV-Flotrac) in a semi-recumbent position, during PLR and after volume expansion (500 ml saline). Patients were responders to volume expansion if SV-TTE increased > or = 15%.

Results: Four patients were excluded. No patients received vasoactive drugs. Seven patients presented septic hypovolemia. PLR-induced changes in SV-TTE and in SV-Flotrac were correlated (r2 = 0.56, P < 0.0001). An increase in SV-TTE > or = 13% during PLR was predictive of response to volume expansion with a sensitivity of 100% and a specificity of 80%. An increase in SV-Flotrac > or =16% during PLR was predictive of response to volume expansion with a sensitivity of 85% and a specificity of 90%. There was no difference between the area under the ROC curve for PLR-induced changes in SV-TTE (AUC = 0.96 +/- 0.03) or SV-Flotrac (AUC = 0.92 +/- 0.05). Volume expansion-induced changes in SV-TTE correlated with volume expansion-induced changes in SV-Flotrac (r2 = 0.77, P < 0.0001). In all patients, the highest plateau value of SV-TTE recorded during PLR was obtained within the first 90 s following leg elevation, whereas it was 120 s for SV-Flotrac.

Conclusions: PLR-induced changes in SV-Flotrac are able to predict the response to volume expansion in spontaneously breathing patients without vasoactive support.

Figure 1

PLR-induced changes in SV-TTE and in SV-Flotrac in responders and non-responders. Box plots and individual values of passive leg raising (PLR)-induced changes in stroke volume measured with transthoracic echocardiography (SV-TTE) and with Vigileo™ (SV-Flotrac) in responders (Rs) and in non-responders (NRs).

Figure 2

Relation between PLR-induced changes in SV-TTE and SV-Flotrac. Relation between passive leg raising (PLR)-induced changes in stroke volume measured with transthoracic echocardiography (SV-TTE) and with Vigileo™ (SV-FloTrac).

Figure 3

Relation between VE-induced changes in SV-TTE and SV-Flotrac. Relation between volume expansion (VE)-induced changes in stroke volume measured with transthoracic echocardiography (SV-TTE) and with Vigileo™ (SV-FloTrac).

Figure 4

ROC curves for predicting response to volume expansion. Receiver operating characteristic (ROC) curves comparing the ability of passive leg raising (PLR)-induced changes in stroke volume measured with transthoracic echocardiography (SV-TTE) and with Vigileo™ (SV-Flotrac) to discriminate responders and non-responders following volume expansion.

Figure 5

Comparison between SV-TTE and SV-Flotrac at baseline, during PLR, before VE and after VE. Bland-Altman plots between stroke volume measured by transthoracic echocardiography (SV-TTE) and by Vigileo™ (SV-Flotrac) at baseline, during passive leg raising, before and after volume expansion. The continuous lines show the mean difference (bias) and the dotted lines show the 95% limits of agreement (two standard deviations).