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

Abstract

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 ( ρ_SORA = 0.496, P_SORA = .003, vs ρ_VENT = 0.161, P_VENT = .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.

Keywords: ScvO; correlation; thenar StO; thenar muscle oxygenation.