SignificanceAnemia is a common problem in preterm neonates, and red blood cell transfusion (RBCT) is used to improve oxygen delivery. However, RBCT is associated with complications, although an increase in cerebral oxygenation has been documented, and no universally accepted biomarker for the need for transfusion (i.e., the concentration of hemoglobin in the blood) has been defined.AimWe used a hybrid optical device (BabyLux device) that merges time-domain near-infrared spectroscopy (TD-NIRS) and diffuse correlation spectroscopy (DCS) to potentially obtain a better assessment of the cerebral effects of RBCT compared with previous studies using continuous wave (CW) spatially resolved NIRS.ApproachEighteen clinically stable preterm neonates were assessed before and after RBCT by the BabyLux device as five repetitions of 60 s measurement (with 1 s acquisition time), estimating the cerebral blood flow (CBF) as a blood flow index (BFI), the total hemoglobin concentration (tHb), and the cerebral tissue oxygen saturation (StO2). StO2 was also continuously monitored by a commercial CW-NIRS device, as well as peripheral saturation, SpO2. Tissue oxygen extraction (TOE) and cerebral metabolic rate of oxygen consumption (tCMRO2) were computed, and the Wilcoxon signed-rank test for paired data was performed, comparing the data acquired before and after RBCT.ResultsThe BabyLux data from four neonates did not meet quality criteria and were discarded. After the transfusion, tHb and StO2 (measured both with TD-NIRS and CW-NIRS devices) significantly increased, causing a significant decrease in TOE. CW-NIRS showed a wider dispersion of StO2 data compared with TD-NIRS. However, CBF did not decrease proportionally but the variation was high, as well as for tCMRO2.ConclusionsThe results confirm previous CW-NIRS studies, but the wide variability of BFI makes the effects of RBCT on cerebral metabolism uncertain.
SignificanceCritically ill newborns are at risk of brain damage from cerebrovascular disturbances. A cerebral hemodynamic monitoring system would have the potential role to guide targeted intervention.AimTo obtain, in a population of newborn infants, simultaneous near-infrared spectroscopy (NIRS)-based estimates of cerebral tissue oxygen saturation (StO2) and blood flow during variations of carbon dioxide tension (pCO2) levels within physiologic values up to moderate permissive hypercapnia, and to examine if the derived estimate of metabolic rate of oxygen would stay constant, during the same variations.ApproachWe enrolled clinically stable mechanically ventilated newborns at postnatal age >24 h without brain abnormalities at ultrasound. StO2 and blood flow index were measured using a non-invasive device (BabyLux), which combine time-resolved NIRS and diffuse-correlation spectroscopy. The effect of changes in transcutaneous pCO2 on StO2, cerebral blood flow (CBF), and cerebral metabolic rate of oxygen index (tCMRO2i) were estimated.ResultsTen babies were enrolled and three were excluded. Median GA at enrollment was 39 weeks and median weight 2720 g. StO2 increased 0.58% (95% CI 0.55; 0.61, p < 0.001), CBF 2% (1.9; 2.3, p < 0.001), and tCMRO2 0.3% (0.05; 0.46, p = 0.017) per mmHg increase in pCO2.ConclusionsBabyLux device detected pCO2-induced changes in cerebral StO2 and CBF, as expected. The small statistically significant positive relationship between pCO2 and tCMRO2i variation is not considered clinically relevant and we are inclined to consider it as an artifact.
Anemia is a common problem in preterm neonates, and red blood cell transfusion (RBCT) is used to improve oxygen delivery. In order to limit the risk of possible complications new strategies to minimize the need for RBCTs are needed, as assessment of hemoglobin concentration in blood ([Hb]) alone appears to be an inadequate biomarker. In this study, we search for hemodynamic and metabolic thresholds to help define the need of RBCT in anemic newborns. The effect of RBCTs on cerebral tissue oxygen saturation (StO2) and blood flow (measured as Blood Flow Index, BFI) was estimated using a non-invasive hybrid diffuse optical device that combines Time Domain NIRS (TD-NIRS) and Diffuse Correlation Spectroscopy (DCS) techniques (BabyLux device). We enrolled 18 clinically stable neonates receiving RBCT at Neonatal Intensive Care Unit (NICU) of Ospedale Maggiore Policlinico in Milan. Tissue oxygen extraction (TOE) and the cerebral metabolic rate of oxygen consumption index (CMRO2I) were computed, the Wilkinson signed rank test for paired data was performed to compare data before and after RBCT. Preliminary results are in accordance with previous publications as regards cerebral oxygenation: a significant increase in StO2 (from 56.62 ± 5.20% to 63.85 ± 4.95%, p<0.05) and reduction in TOE (from 41.35 ± 5.9 % to 31.04 ±5.41%, p<0.05) were observed. The response in cerebral blood flow was smaller (only 10%) but also more variable, so conclusions regarding the effect of transfusion on cerebral oxygen metabolism are still uncertain.
We assessed the sensitivity of 1D and 2D homogeneous photon diffusion models for Time Domain NIRS in estimating preterm and term neonates’ cerebral hemodynamic parameters simulated by Monte Carlo methods on realistic 3D anatomical meshes.
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