Skeletal muscle oxygen saturation estimates mixed venous oxygen saturation in patients with severe left heart failure
© BioMed Central Ltd. 2007
Published: 22 March 2007
Low cardiac output states, such as left heart failure, are characterized by a preserved oxygen extraction ratio compared with severe sepsis. Near-infrared spectroscopy (NIRS) allows noninvasive estimation of skeletal muscle tissue oxygenation (StO2). The aim of study was to determine 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.
Sixty-five patients with severe left heart failure due to primary heart disease were divided into two groups: Group A were patients without (n = 24) and Group B were patients with (n = 41) additional severe sepsis/septic shock. The thenar muscle StO2 was measured using NIRS.
In Group A StO2 was lower compared with Group B and healthy volunteers (58 ± 13% vs 90 ± 7% vs 84 ± 4%, P < 0.001). StO2 was higher in Group B compared with healthy volunteers (P = 0.02). In Group A StO2 correlated with SvO2 (r = 0.689, P = 0.002), and StO2 overestimated SvO2 (bias: -2.3%, precision: 4.6%). In Group A changes of StO2 correlated to changes of SvO2 (r = 0.836, P < 0.001; ΔSvO2 = 0.84 × ΔStO2 – 0.67). In Group B important disagreement between these variables was present. Plasma lactate concentrations negatively correlated with StO2 values only in group A (r = -0.522, P = 0.009; lactate = -0.104 × StO2 + 10.25).
Exact numerical values of StO2 are not equivalent to those of SvO2. However, for clinical purpose, StO2 values could be used for fast noninvasive SvO2 estimation; and the trend of StO2 may be substituted for the trend of SvO2 in severe left heart failure without additional severe sepsis or septic shock.