Resonance Raman Spectroscopy Tissue Oxygenation Measurements in Neonates

Abstract

<b><i>Introduction:</i></b> Current oxygen monitoring by pulse oximetry has limitations and cannot provide estimates of the oxygen content in the microvasculature, where oxygen is used. Resonance Raman spectroscopy (RRS) provides noninvasive microvascular oxygen measurement. The objectives of this study were to (i) measure the correlation between preductal RRS microvascular oxygen saturations (RRS-StO2) and central venous oxygen saturation (S<sub>CV</sub>O<sub>2</sub>), (ii) develop normative data for RRS-StO2 measurements in healthy preterm infants, and (iii) determine the effect of blood transfusion on RRS-StO2. <b><i>Methods:</i></b> Thirty-three buccal and thenar RRS-StO2 measurements were performed in 26 subjects to correlate RRS-StO2 with S<sub>CV</sub>O<sub>2</sub>. Thirty-one measurements were performed in 28 subjects to develop normative RRS-StO2 values, and eight subjects were enrolled in the transfusion group to assess changes in RRS-StO2 with blood transfusion. <b><i>Results:</i></b> There were good correlations for buccal (<i>r</i> = 0.692) and thenar (<i>r</i> = 0.768) RRS-StO2 versus S<sub>CV</sub>O<sub>2</sub>. The median RRS-StO2 in healthy subjects was 76% (IQR 68.7–80.8). There was a significant increase of 7.8 ± 4.6% in the thenar RRS-StO2 after blood transfusion. <b><i>Conclusions:</i></b> RRS appears to be a safe and noninvasive means of monitoring microvascular oxygenation. Thenar RRS-StO2 measurements are more feasible and practical to use than buccal. In healthy preterm infants, the median RRS-StO2 was calculated based on measurements across various gestational age and gender. More studies evaluating the effects of gestational age of RRS-StO2 in various critical clinical settings are needed to confirm the findings.

Quantitative Optical Imaging of Oxygen in Brain Vasculature

“…124,125 It has also been used noninvasively in animal models and even in neonates. 126,127 Spatially resolved Raman microscopy for sO 2 determination has been achieved in the brain in vivo by Brazhe et al 123 They used RRS to visualize the oxygenation in arterioles and venules in anesthetized mouse cortices with a 532 nm excitation to minimize photodamage (Figure 6j). However, the lack of spatial and temporal resolution is a major concern for in vivo measurements with RRS.…”

“…By comparing the intensity of the higher wavenumber HbO 2 peak to the sum intensity of the HbO 2 and HbR peak pair, a qualitative estimation of sO 2 can be determined (Figure h,i) . RRS has been used for a few in vivo oxygen saturation studies in a variety of tissues with good agreement with traditional oximetry methods. , It has also been used noninvasively in animal models and even in neonates. , Spatially resolved Raman microscopy for sO 2 determination has been achieved in the brain in vivo by Brazhe et al They used RRS to visualize the oxygenation in arterioles and venules in anesthetized mouse cortices with a 532 nm excitation to minimize photodamage (Figure j). However, the lack of spatial and temporal resolution is a major concern for in vivo measurements with RRS.…”