Do ScvO2 variations induced by passive leg raising predict fluid responsiveness? A prospective study

Abstract

Objective: The present study investigates whether ScvO₂ variations induced by passive leg raising (PLR) are able to predict fluid responsiveness (FR) in mechanically ventilated patients.

Design: A monocentric prospective clinical study.

Setting: An intensive care division in a tertiary hospital.

Patients: The inclusion criteria were elective postoperative cardiac surgery patients who were over 18 years old, deeply sedated, mechanically ventilated and needed volume expansion (VE). Fluid responders (R) were defined as patients who increased their left ventricular outflow tract velocity time integral (VTI) ≥15% after VE.

Intervention: In patients included in this study, continuous ScvO₂ monitoring (CeVOX device, Pulsion Medical Systems) and VTI (transthoracic echocardiography) were measured simultaneously before and during a PLR test and before and after VE (with 500 ml of saline).

Measurements and main results: Thirty-three consecutive patients were included in this study. In 15 patients with a positive PLR test (increase in VTI ≥15%), ScvO₂ increased during PLR by 9 ± 4%. In the 18 patients with a negative PLR test, ScvO₂ did not significantly change during PLR. VE increased ScvO₂ by 9 ± 6% and 2 ± 4% in responders and nonresponders, respectively. If ScvO₂ increased by >4% during the PLR test, then a positive VTI response (≥15%) was diagnosed with a sensitivity of 93% (68-99%) and a specificity of 94% (63-99%) (Area under the receiver operating characteristic curve 0.92 ± 0.58, p < 0.05). Moreover, ScvO₂ variations were able to distinguish responders to VE from nonresponders to VE with a sensitivity of 87% (68-99%) and a specificity of 89% (63-99%) (Area under the receiver operating characteristic curve 0.89 ± 0.07, p < 0.05).

Conclusions: ScvO₂ variation induced by PLR is a reliable, minimally invasive parameter for predicting FR at the postoperative cardiac surgery bedside of mechanically ventilated, critically ill patients.

Keywords: ScvO2; cardiac output; central venous oxygen saturation; echocardiography; fluid responsiveness; hemodynamic; passive leg raising.

FIGURE 1

Study protocol

FIGURE 2

ROC curves comparing the ability of ScvO₂ variations to discriminate responders (CI increases ≥15% after volume expansion and nonresponders (CI increases <15% after PLR)

FIGURE 3

ROC curves comparing the ability of ScvO₂ variations to discriminate responders (CI increases ≥15% after volume expansion and nonresponders (CI increases <15% after VE)