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

Abstract

Objective: 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.

Design: Prospective observational study.

Setting: A 26-bed medical-surgical intensive care unit at a university-affiliated hospital.

Patients: 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.

Measurements: 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%.

Results: 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%.

Conclusions: 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.