Correlation of anterior cerebral artery resistive index with early comorbidities in preterm neonates

Subarachnoid haemorrhage (SAH) is a form of stroke that is associated with substantial morbidity, often as a result of cerebral ischaemia that occurs in the following days. These delayed deficits in blood flow have been traditionally attributed to cerebral vasospasm (the narrowing of large arteries), which can lead to cerebral infarction and poor neurological outcome. Data from recent studies, however, show that treatment of vasospasm in patients with SAH, using targeted medication, does not translate to better neurological outcomes, and argue against vasospasm being the sole cause of the delayed ischaemic complications. Cerebral autoregulation-a mechanism that maintains stability of cerebral blood flow in response to changes in cerebral perfusion pressure-has been reported to fail after SAH, often before vasospasm becomes apparent. Failure of autoregulation, therefore, has been implicated in development of delayed cerebral ischaemia. In this Review, we summarize current knowledge about the clinical effect of disturbed cerebral autoregulation following aneurysmal SAH, with emphasis on development of delayed cerebral ischaemia and clinical outcome, and provide a critical assessment of studies of cerebral autoregulation in SAH with respect to the method of blood-flow measurement. Better understanding of cerebral autoregulation following SAH could reveal mechanisms of blood-flow regulation that could be therapeutically targeted to improve patient outcome. Show more

The absence of cerebral autoregulation in preterm infants has been associated with adverse outcome, but its bedside assessment in the immature brain is problematic. We used spatially resolved spectroscopy to continuously measure cerebral oxygen saturation (expressed as a tissue-oxygenation index) and used the correlation of tissue-oxygenation index with spontaneous fluctuations in mean arterial blood pressure to assess cerebral autoregulation. The tissue-oxygenation index and mean arterial blood pressure were continuously measured in very premature infants (n = 24) of mean (+/-SD) gestational age of 26 (+/-2.3) weeks at a mean postnatal age of 28 (+/-22) hours. The correlation between mean arterial blood pressure and tissue-oxygenation index in the frequency domain was assessed by using cross-spectral analysis techniques (coherence and transfer-function gain). Values of coherence reflect the strength of linear correlation, whereas transfer-function gain reflects the amplitude of tissue-oxygenation index changes relative to mean arterial blood pressure changes. High coherence (coherence > or = 0.5) values were found in 9 infants who were of lower gestational age, lower birth weight, and lower mean arterial blood pressure than infants with coherence of or = 0.5 predicted mortality with a positive predictive value of 67% and negative predictive value of 100%. In multifactorial analysis, coherence alone was the best predictor of mortality and Clinical Risk Index for Babies score alone was the best predictor of coherence. High coherence between mean arterial blood pressure and tissue-oxygenation index indicates impaired cerebral autoregulation in clinically sick preterm infants and is strongly associated with subsequent mortality. Cross-spectral analysis of mean arterial blood pressure and tissue-oxygenation index has the potential to provide continuous bedside assessment of cerebral autoregulation and to guide therapeutic interventions. Show more

Preterm birth (gestational age 95% of preterm infants who receive modern neonatal and pediatric care now survive into adulthood. The earliest birth cohorts to benefit from those advances are now in their 4th and 5th decades of life. A growing number of large cohort studies have investigated the long-term health sequelae in adulthood. Evidence has consistently shown that adult survivors of preterm birth have increased risks of chronic disorders involving various organ systems, including cardiovascular, endocrine/metabolic, respiratory, renal, neurodevelopmental, and psychiatric disorders, which either persist from childhood into adulthood or sometimes first manifest in adulthood. These disorders also lead to moderately (30% to 50%) increased mortality risks during early to mid-adulthood among persons born preterm compared with full-term, and even higher risks among those born at the earliest gestational ages. However, the majority of persons born preterm have low absolute risks of these outcomes and good self-reported quality of life in adulthood. Priorities for future research include the assessment of long-term health sequelae of preterm birth in racially and economically diverse populations, additional follow-up of existing cohorts into older adulthood, elucidation of outcomes by preterm birth subtype (e.g., different underlying causes) to improve risk stratification, and identification of protective factors that will support the long-term health trajectory and well-being of preterm-born adults. Show more