New developments in cerebral blood flow autoregulation analysis in preterm infants: a mechanistic approach

Background: Impaired autoregulation capacity implies that changes in cerebral perfusion follow changes in blood pressure; however, no analytical method has explored such a signal causality relationship in infants. We sought to develop a method to assess cerebral autoregulation from a mechanistic point of view and explored the predictive capacity of the method to classify infants at risk for adverse outcomes. Methods: The partial directed coherence (PDC) method, which considers synchronicity and directionality of signal dependence across frequencies, was used to analyze the relationship between spontaneous changes in mean arterial pressure (MAP) and the cerebral tissue oxygenation index (TOI). PDCMAP >> TOI indicated that changes in TOI were induced by MAP changes, and PDCTOI >> MAP indicated the opposite. Results: The PDCMAP >> TOI and PDCTOI >> MAP values differed. PDCMAP >> TOI adjusted by gestational age predicted low superior vena cava flow (<= 41 ml/kg per min), with an area under the receiver operating characteristic curve of 0.72 (95% CI: 0.63-0.81; P < 0.001), whereas PDCTOI >> MAP did not. The adjusted pPDC(MAP >> TOI) (the average value per patient) predicted severe intracranial hemorrhage and mortality. Conclusion: PDCMAP >> TOI allows for a noninvasive physiological interpretation of the pressure autoregulation process in neonates. PDCMAP >> TOI is a good classifier for infants at risk of brain hypoperfusion and adverse outcomes.