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

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 (StO(2)). The aim of the study was to determine the relationship between StO(2 )and mixed venous oxygen saturation (SvO(2)) 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 StO(2 )was measured using NIRS in the patients and in 15 healthy volunteers. RESULTS: StO(2 )was lower in group A than in group B and in healthy volunteers (58 ± 13%, 90 ± 7% and 84 ± 4%, respectively; P < 0.001). StO(2 )was higher in group B than in healthy volunteers (P = 0.02). In group A StO(2 )correlated with SvO(2 )(r = 0.689, P = 0.002), although StO(2 )overestimated SvO(2 )(bias -2.3%, precision 4.6%). In group A changes in StO(2 )correlated with changes in SvO(2 )(r = 0.836, P < 0.001; ΔSvO(2 )= 0.84 × ΔStO(2 )- 0.67). In group B important differences between these variables were observed. Plasma lactate concentrations correlated negatively with StO(2 )values only in group A (r = -0.522, P = 0.009; lactate = -0.104 × StO(2 )+ 10.25). CONCLUSION: Skeletal muscle StO(2 )does not estimate SvO(2 )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, StO(2 )values could be used to provide rapid, noninvasive estimation of SvO(2); furthermore, the trend in StO(2 )may be considered a surrogate for the trend in SvO(2). Trial Registration: NCT00384644