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Variations in near-infrared spectroscopy-derived oxygen downslope during a vascular occlusion test in critically ill patients: relationship with outcome

Introduction

Near-infrared spectroscopy (NIRS) with a vascular occlusion test (VOT) can be used to extrapolate information regarding the tissue oxygen extraction rate. We explored the meaning of variations in tissue oxygen saturation downslope (StO2down) during a VOT in critically ill patients.

Methods

In this prospective observational study, NIRS (thenar eminence) was applied every day in 93 patients admitted to the ICU. A VOT was performed using a 40% StO2 target. The slope of the desaturation curve was assessed separately for the first part (StO2 down1) and the last part (StO2 down2) of the curve and the difference between Down2 - Down1 was calculated.

Results

No significant differences were seen in StO2 Down1 or Down2 between ICU survivors (n = 76) and ICU nonsurvivors (n = 17) over the first 10 days in the ICU, while Down2 - Down1 was higher in ICU nonsurvivors (Figure 1). Patients in the upper quartile of mean Down2 - Down1 showed the highest 90-day mortality (P = 0.014).

figure1

Figure 1

Conclusion

ICU nonsurvivors tended to show a flattening in the last part of the desaturation curve during a VOT, suggesting a reduced tissue oxygen extraction. This may depend on microvascular dysfunction and/or cellular hypometabolic status.

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Donati, A., Damiani, E., Carsetti, A. et al. Variations in near-infrared spectroscopy-derived oxygen downslope during a vascular occlusion test in critically ill patients: relationship with outcome. Crit Care 19, P141 (2015). https://doi.org/10.1186/cc14221

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Keywords

  • Oxygen Saturation
  • Extraction Rate
  • Prospective Observational Study
  • Tissue Oxygen
  • Microvascular Dysfunction