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

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Abstract

Objective

To validate thenar oxygen saturation (StO2) measured by near-infrared spectroscopy (NIRS) as a noninvasive estimation of central venous saturation (ScvO2) 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 ScvO2, and StO2 measured simultaneously on inclusion. Patients were divided into two groups according to ScvO2 values: group A, with ScvO2 < 70%, and group B, with ScvO2 ≥ 70%.

Results

Forty patients were studied. StO2 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 ScvO2 and StO2 showed a significant Pearson correlation (r = 0.39, P 0.017). For a StO2 value of 75%, sensitivity was 0.44, specificity 0.93, positive predictive value 0.92, and negative predictive value 0.52 for detecting ScvO2 values lower than 70%.

Conclusions

StO2 correlates with ScvO2 in normotensive patients with severe sepsis or septic shock. We propose a StO2 cut-off value of 75% as a specific, rapid, noninvasive first step for detecting patients with low ScvO2 values. Further studies are necessary to analyze the role of noninvasive StO2 measurement in future resuscitation algorithms.

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