Thenar oxygen saturation measured by near infrared spectroscopy as a noninvasive predictor of low central venous oxygen saturation in septic patients.

Abstract

To validate thenar oxygen saturation (StO(2)) measured by near-infrared spectroscopy (NIRS) as a noninvasive estimation of central venous saturation (ScvO(2)) in septic patients. Prospective observational study. A 26-bed medical-surgical intensive care unit at a university-affiliated hospital. Patients consecutively admitted to the ICU in the early phase of severe sepsis and septic shock, after normalization of blood pressure with fluids and/or vasoactive drugs. We recorded demographic data, severity score, hemodynamic data, and blood lactate, as well as ScvO(2), and StO(2) measured simultaneously on inclusion. Patients were divided into two groups according to ScvO(2) values: group A, with ScvO(2) < 70%, and group B, with ScvO(2) > or = 70%. Forty patients were studied. StO(2) was significantly lower in group A than in group B (74.7 +/- 13.0 vs. 83.3 +/- 6.2, P 0.018). No differences in age, severity score, hemodynamics, vasoactive drugs, or lactate were found between groups. Simultaneously measured ScvO(2) and StO(2) showed a significant Pearson correlation (r = 0.39, P 0.017). For a StO(2) value of 75%, sensitivity was 0.44, specificity 0.93, positive predictive value 0.92, and negative predictive value 0.52 for detecting ScvO(2) values lower than 70%. StO(2) correlates with ScvO(2) in normotensive patients with severe sepsis or septic shock. We propose a StO(2) cut-off value of 75% as a specific, rapid, noninvasive first step for detecting patients with low ScvO(2) values. Further studies are necessary to analyze the role of noninvasive StO(2) measurement in future resuscitation algorithms.