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Measurement of cerebral oxygenation in preterm infants: is it useful? TOPUN AUSTIN Centre for Perinatal Neuroscience, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK. doi: 10.1111/dmcn.12672 This commentary is on the original article by Verhagen et al. on pages 449–455 of this issue.
Despite improvement in survival of extremely preterm infants over the past 20 years, the incidence of brain injury resulting in lifelong neurodisability remains stubbornly static. Alterations in cerebral perfusion and oxygenation have been implicated in the pathogenesis of brain injury; but without reliable quantitative cot-side cerebral monitoring, identifying infants at risk and developing strategies to prevent it have remained elusive. Near-infrared spectroscopy (NIRS) has longed promised to be a valuable clinical monitor for infants receiving intensive care, but has yet to live up to early expectations. For many years the lack of continuous quantitative data meant only relative changes in the concentration of oxygenated and deoxygenated haemoglobin could be measured. However, current commercial instruments all use a ‘multi-detector’ approach, which not only eliminates surface measurements from the skin and skull, but also enables the ratio of oxygenated haemoglobin to total haemoglobin to be measured: expressed as a percentage this equates to the oxygen saturation of the interrogated tissue. The regional cerebral tissue oxygen saturation (rcSO2) reflects predominantly venous oxygen saturation, given the size of the venous compartment. When this measurement is combined with values of arterial oxygen saturation (SpO2) it is possible to calculate the fractional tissue oxygen extraction (FTOE). FTOE reflects the balance between cerebral oxygen supply and consumption. However, the precision of these instruments has been questioned. Using the NIRO 300 (Hamamatsu Photonics K.K., Hamamatsu, Japan), Sorensen et al.1 showed that the within-infant variation was 5.2% when resiting the optode. Hyttel-Sorensen et al.2 compared three commercial NIRS systems on the forearm of adults and found that the abso404 Developmental Medicine & Child Neurology 2015, 57: 401–409
lute values of tissue oxygen saturation (StO2) differed between instruments, although the reproducibility and dynamic range were similar. The varying absolute values between instruments cause the determination of normal ranges and thresholds for infants to be challenging. Data on the association of rcSO2 and long-term neurodevelopmental outcome are limited. Sorensen et al. and more recently Noori et al. have both reported a low rcSO2 on the first day of life to be associated with large intraventricular haemorrhage (IVH), consistent with the ischaemicreperfusion model of IVH;1,3 Alderliesten et al.4 found low rcSO2 associated with lower developmental score at 2 years of age in very preterm infants. Verhagen et al.5 present neurodevelopmental outcome data from a group of preterm infants, all of whom had measurements of cerebral oxygenation made over the first 2 weeks of life. The authors describe an association between both low and high cerebral oxygenation on day 1 and adverse neurodevelopmental sequelae. The amount of time rcSO2 was