Research Highlights

Assessment of tissue oxygen delivery in very low birth weight (VLBW) infants poses a continuing challenge to the neonatologist. Diffuse optical spectroscopy (DOS) is a non-invasive quantitative method able to measure tissue oxy, de-oxy, and total hemoglobin concentrations (Hb-O₂, Hb-R, THC), as well as the mixed arterial-venous tissue hemoglobin saturation (S_TO₂). We hypothesized that DOS may serve as a non-invasive tool to asses tissue oxygen delivery using a blood transfusion model in VLBW infants.

Our objective in this study was to evaluate changes in Hb-O₂, Hb-R, THC, and S_TO₂ using DOS pre and post transfusion in VLBW infants.

DOS measurements of Hb-O₂ and Hb-R were performed on 11 VLBW infants scheduled to receive red blood cell transfusions. Ten were measured before and within 24 hours post transfusion. Seven non-transfused subjects were also measured, in addition to one non-VLBW transfusion subject. All measurements were completed using a four-wavelength frequency-domain tissue oximeter that quantifies tissue absorption and reduced scattering at 690, 750, 810, and 830 nm. The handheld probe was placed on the interscapular region while the subject lay prone during the measurements.

In the transfused subjects, DOS calculations demonstrated significant increases in Hb-O₂ (48±13 vs. 74±20 M, p<0.0001), THC (87±17 vs. 107±24 M, p=0.0007) and S_TO₂ (54±8 vs. 68±6%, p<<0.001) post transfusion. DOS measurements were highly correlated with mean blood hemoglobin increases for all 19 subjects (r=0.88, p<0.0001). Successive measurements over the course of transfusion demonstrated a sigmoidal change in THC and Hb-O₂ values with a time constant of 45±13 minutes and 57±37 minutes, respectively. No significant changes in DOS measurements were found in the non-transfused group when measured on two successive days.

DOS demonstrated significant increases in tissue oxygen delivery resulting from red blood cell transfusion. DOS measurements of tissue hemoglobin changes correlated with invasive blood hemoglobin monitoring. DOS may serve as a non-invasive bedside tool to assess the tissue oxygen supply/demand relationship.

In submission to Pediatrics.