Correlation between Tissue Oxygen Saturation and Global Oxygenation Parameters in Emergency Patients: A Pilot Clinical Study

Yoon, Young Woong; Cho, Young Mo; Kim, Hyung Bin; Ryu, Ji Ho; Park, Maeng Ryul; Min, Mun Ki; Kim, Yong In; Park, Sung Wook

Abstract

PURPOSE
Near-infrared spectroscopy (NIRS) can noninvasively assess changes in tissue oxygen saturation (StOâ‚‚). The primary concern of the current study is to determine whether StOâ‚‚ can be used as a surrogate for global oxygenation parameters such as central venous oxygen saturation (ScvOâ‚‚), lactic acid, and base deficit (BD) in patients presenting to the emergency department (ED).
METHODS
This was a prospective, observational study in patients requiring central venous catheter placement, admitted to the ED with complaints classified as infectious and non-infectious etiology. The NIRS sensor (15 mm probe) was applied on the thenar eminence for at least 3 minutes and ScvOâ‚‚, arterial lactic acid, and BD were measured during insertion of a central venous catheter. Data were analyzed using a simple correlation and Bland-Altman plot.
RESULTS
A total of 120 patients were enrolled in the study and further classified as an infection (n=39) and a noninfection (n=81) group. Lactic acid BD showed significant correlation with StOâ‚‚ in total and in non-infection patients but the degree of correlation was weak and these correlations were not observed in infection patients. Approximately 94% of the difference between StOâ‚‚ and ScvOâ‚‚ was placed within limit of agreement but there was a risk that StOâ‚‚ may overestimate ScvOâ‚‚ when ScvOâ‚‚ becomes lower. When patients were assigned to two groups according to laboratory results (lactic acid 4.0 mmol/L; BD > 3.0 mmol/L; ScvOâ‚‚> 65% or 75%), no significant difference in StOâ‚‚ was observed between the two groups.
CONCLUSION
In ED patients suspected of having systemic hypoperfusion, StOâ‚‚ showed a weak correlation with lactic acid and BD in non-infection patients and no correlation in infection patients. In addition, as ScvOâ‚‚ decreased, the difference between StOâ‚‚ and ScvOâ‚‚ showed a tendency to increase, and StOâ‚‚ was much higher than ScvOâ‚‚ at low ScvOâ‚‚ level. Therefore, before using StOâ‚‚ as surrogate for ScvOâ‚‚, lactic acid and BD in critically ill patients presenting to the ED, further investigation should be conducted to overcome the limitations of NIRS addressed in this study.