Abstract
BACKGROUND Ensuring the adequacy of cerebral oxygen delivery to meet metabolic demand is important in the brain orientated care of newborn infants. Spatially resolved near-infrared spectroscopy (SRS) is an optical method which provides quantitative measurement of the mean cerebral oxygen saturation (SmcO2) at the cotside1. SmcO2 is dependent on both cerebral oxygen delivery and consumption.
AIM the aim of this study was to use measurements of SmcO2 obtained by SRS and cerebral blood flow (CBF) measured using differential spectroscopy to obtain absolute values of cerebral oxygen delivery (CDO2) and cerebral metabolic rate (CMRO2) during the first hours of life in a cohort of preterm infants undergoing intensive care.
METHODS Fifteen preterm infants born at a median (range) postmenstrual age of 25 (23–31) weeks were studied. Their median birthweight was 806 (512–1800)g and the median age at study was 12 (4–35) hours of age. All infants required ventilatory support. SmcO2 data was collected using a NIRO300 spectrophotometer (Hamamatsu Photonics, K.K., Japan). Cerebral blood flow (CBF) was measured using the oxygen bolus technique. CMRO2 was calculated from SmcO2 and CBF2.
RESULTS the median (range) SmcO2 was 56.7 (46.6–78.5%), CDO2 1.35 (0.88–3.62) ml O2/100g/min, CMRO2 0.64 (0.36–1.73) ml O2/100g/min. There was a significant linear relationship between CMRO2 and CDO2 (r=0.7, p=0.004). There was also a significant correlation between SmcO2 and age at study (r=0.63, p=0.01).
DISCUSSION the values of CMRO2 obtained using this technique are low, but consistent with other studies in the newborn. There is evidence of some degree of perfusion-metabolism coupling in extremely preterm infants in the first hours of life. Infants with a very low SmcO2 as a result of a mismatch between CDO2 and CMRO2 may be more vulnerable to hypoxic-ischaemic brain injury.
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Austin, T., Leung, T., Wong, F. et al. 17 Relationship Between Cerebral Oxygen Delivery, Cerebral Metabolic Rate and the Mean Cerebral Oxygen Saturation in Preterm Infants. Pediatr Res 58, 357 (2005). https://doi.org/10.1203/00006450-200508000-00046
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DOI: https://doi.org/10.1203/00006450-200508000-00046