The first week of postnatal life is a period of transition for both pulmonary and systemic vascular flow patterns. Owing to associated shunts and altered systemic/pulmonary blood flow, neonates with congenital heart defect (CHD) are at particular risk for disrupted end-organ perfusion and oxygen delivery, including that of the brain. Near-infrared spectroscopy (NIRS) measures venous-weighted cerebral oxygen saturation (CSat) at the frontal cortex, serving as an indirect reflection of cerebral blood flow. CSat is impacted by factors such as tissue perfusion, systemic oxygenation, regional oxygen extraction and haemoglobin levels, all of which are affected by cardiac function and vascular supply 1, 2. Cerebral fractional tissue oxygen extraction (cFTOE) reflects the balance between cerebral oxygen utilisation and oxygen delivery, and it is operationally defined as (preductal SpO2—CSat)/preductal SpO2. As such, cFTOE can provide insight into cerebral oxygen utilisation. Increased cFTOE can be due to decreased oxygen delivery or increased oxygen consumption not met by associated increase in delivery. Likewise, decreased cFTOE can indicate that the brain is using less oxygen or that oxygen delivery has increased relative to utilisation 3. Data on CSat and cFTOE as cerebrovascular metrics in neonates with CHD during the period of postnatal adaptation are limited. Elements of anterior cerebral artery (ACA) Doppler such as resistive index (RI) and pulsatility index (PI) assess vascular resistance and flow characteristics in the frontal cortex and have been shown to correspond to cerebral perfusion pressure 4. Abnormal RI is a recognised indicator of such newborn pathologies as increased intracranial pressure, brain injury and diastolic steal 5-7. This study has made a notable contribution to the literature by applying these established bedside tools to a vulnerable and complex group of patients (neonates with CHD) during a time of critical transitional physiology (postnatal adaptation). The authors recruited 34 neonates with various types of CHD and analysed 142 concomitant data measurements of NIRS and daily ultrasound Doppler over the first 7 days of life. They used mixed-effects models to evaluate the relationship between CSat/cFTOE and RI/PI-ACA, adjusting for time since birth, pCO2 and haemoglobin levels. The authors found a decline in CSat and rise in cFTOE throughout the first week of life in neonates with CHD, which aligns with findings from prior research 8. RI and PI both increased over the time period, indicating increased resistance to flow velocities. The authors also reported statistically significant associations between CSat/cFTOE and simultaneous RI/PI values. The findings suggest a progressive increase in oxygen extraction, possibly related to diminished blood flow, impaired oxygen delivery or increased metabolic demand during postnatal transition. The authors theorise that this may be partly owing to altered adaptation due to shunts and abnormal anatomy. Despite the variability of the study population, the findings supported consistent directional trends in NIRS and ultrasound. While these results are meaningful, an even greater impact will be gained in translating the findings to earlier detection/management of cerebral hypoperfusion in order to improve neurodevelopmental outcomes. URL LINK: https://ebneo.org/ebneo-commentary-cerebral-saturation-and-fractional-tissue-oxygen-extraction-and-anterior-cerebral-artery-doppler. Ashley L. Lynch: conceptualization, writing – original draft. Ethan L. Gillett: writing – review and editing. The authors have nothing to report. The authors declare no conflicts of interest. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.
Lynch et al. (2026) studied this question.