ScvO2 As a Marker to Define Fluid Responsiveness

BACKGROUND: Definition of the hemodynamic response to volume expansion (VE) could be useful in shocked critically ill patients in absence of cardiac index (CI) measurements. The aim of this study is to evaluate whether central venous oxygen saturation variations (ΔScvO(2)) after VE could be an alternative to classify responders (R) and nonresponders (NR) to volume therapy. METHODS: A total of 30 patients requiring VE were included in this prospective cohort study, all equipped with radial arterial line and pulmonary artery catheters. CI, mixed venous oxygen saturation (SvO(2)) and ScvO(2) were measured before and after VE. CI, SvO(2), and ScvO(2) changes after volume were analyzed using linear regression. Receiver operating characteristics curve analysis was used to test their ability to distinguish R and NR. RESULTS: ΔScvO(2) and SvO(2) variations after VE (ΔSvO(2)) were significantly correlated with CI changes (ΔCI) after VE (r = 0.67 and r = 0.49, p < 0.001, respectively). A ΔScvO(2) threshold value of 4% allowed the definition of R and NR patients with 86% sensitivity (95%CI; 57-98%) and 81% specificity (95%CI; 54-96%). CONCLUSIONS: ScvO2 variations after VE was able to categorize VE efficiently and could be suggested as an alternative marker to define fluid responsiveness in absence of invasive CI measurement.