Thenar Muscle Oxygen Saturation Levels: A Surrogate for Central Venous Oxygen Saturation?

PURPOSE: Shock is associated with increased tissue oxygen extraction. Near-infrared spectroscopy-derived thenar muscle tissue oxygenation (StO2 ) levels can provide an estimate of the oxygen supply-demand balance at the tissue level. We hypothesized that thenar StO2 levels would correlate with central venous oxygen saturation (ScvO2 ) levels, the gold standard for global tissue oxygen extraction in the body.

METHODS: We prospectively enrolled 60 pediatric subjects admitted to pediatric intensive care unit or who underwent cardiac catheterization from September 2015 to March 2018. Thenar StO2 levels were measured using the InSpectra StO2 probe. Concurrent measurements of ScvO2 and peripheral tissue oxygenation (StO2 ) were achieved through simultaneous testing. For ScvO2 , a central line placed in the superior vena cava was utilized for serum specimen collection, while the InSpectra probe recorded StO2 measurements from the thenar eminence of the patient's right hand.

RESULTS: Sixty observations of thenar StO2 and ScvO2 levels were derived from 60 subjects. Mean thenar StO2 levels were 74.72 ± 11.18% and displayed significant correlation with paired ScvO2 measurements ( m = 72.17 ± 9.77%; ρ = 0.317, P = .018). Correlation was much more significant in subjects who were not on mechanical ventilatory support as opposed to those who were on it ( ρSORA = 0.496, PSORA = .003, vs ρVENT = 0.161, PVENT = .433). A thenar StO2 of 73% had a sensitivity of 80% and a specificity of 77.8% in predicting an ScvO2 of less than 65%.

CONCLUSION: This is the first study to report correlation of thenar StO2 and ScvO2 levels in children. Our study results show a significant correlation between these levels. Thenar StO2 measurements may have a role in the bedside management of critically ill children in whom ScvO2 monitoring is not available.