Research

Skeletal muscle oxygen saturation does not estimate mixed venous oxygen saturation in patients with severe left heart failure and additional severe sepsis or septic shock

Matej Podbregar and Hugon Možina

Clinical Department for Intensive Care Medicine, University Clinical Centre, Zaloska 7, 1000 Ljubljana, Slovenia

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Critical Care 2007, 11:R6doi:10.1186/cc5153

Published:	16 January 2007

See related commentary by Puyana and Pinsky, http://ccforum.com/content/11/1/116

Abstract

Introduction

Low cardiac output states such as left heart failure are characterized by preserved oxygen extraction ratio, which is in contrast to severe sepsis. Near infrared spectroscopy (NIRS) allows noninvasive estimation of skeletal muscle tissue oxygenation (StO₂). The aim of the study was to determine the relationship between StO₂ and mixed venous oxygen saturation (SvO₂) in patients with severe left heart failure with or without additional severe sepsis or septic shock.

Methods

Sixty-five patients with severe left heart failure due to primary heart disease were divided into two groups: groups A (n = 24) and B (n = 41) included patients without and with additional severe sepsis/septic shock, respectively. Thenar muscle StO₂ was measured using NIRS in the patients and in 15 healthy volunteers.

Results

StO₂ was lower in group A than in group B and in healthy volunteers (58 ± 13%, 90 ± 7% and 84 ± 4%, respectively; P < 0.001). StO₂ was higher in group B than in healthy volunteers (P = 0.02). In group A StO₂ correlated with SvO₂ (r = 0.689, P = 0.002), although StO₂ overestimated SvO₂ (bias -2.3%, precision 4.6%). In group A changes in StO₂ correlated with changes in SvO₂ (r = 0.836, P < 0.001; ΔSvO₂ = 0.84 × ΔStO₂ - 0.67). In group B important differences between these variables were observed. Plasma lactate concentrations correlated negatively with StO₂ values only in group A (r = -0.522, P = 0.009; lactate = -0.104 × StO₂ + 10.25).

Conclusion

Skeletal muscle StO₂ does not estimate SvO₂ in patients with severe left heart failure and additional severe sepsis or septic shock. However, in patients with severe left heart failure without additional severe sepsis or septic shock, StO₂ values could be used to provide rapid, noninvasive estimation of SvO₂; furthermore, the trend in StO₂ may be considered a surrogate for the trend in SvO₂.

Trial Registration: NCT00384644