Cerebral Autoregulation, Brain Injury, and the Transitioning Premature Infant

Abstract

Improvements in clinical management of the preterm infant have reduced the rates of the two most common forms of brain injury, such as severe intraventricular hemorrhage and white matter injury, both of which are contributory factors in the development of cerebral palsy. Nonetheless, they remain a persistent challenge and are associated with a significant increase in the risk of adverse neurodevelopment outcomes. Repeated episodes of ischemia–reperfusion represent a common pathway for both forms of injury, arising from discordance between systemic blood flow and the innate regulation of cerebral blood flow in the germinal matrix and periventricular white matter. Nevertheless, establishing firm hemodynamic boundaries, as a part of neuroprotective strategy, has challenged researchers. Existing measures either demonstrate inconsistent relationships with injury, as in the case of mean arterial blood pressure, or are not feasible for long-term monitoring, such as cardiac output estimated by echocardiography. These challenges have led some researchers to focus on the mechanisms that control blood flow to the brain, known as cerebrovascular autoregulation. Historically, the function of the cerebrovascular autoregulatory system has been difficult to quantify; however, the evolution of bedside monitoring devices, particularly near-infrared spectroscopy, has enabled new insights into these mechanisms and how impairment of blood flow regulation may contribute to catastrophic injury. In this review, we first seek to examine how technological advancement has changed the assessment of cerebrovascular autoregulation in premature infants. Next, we explore how clinical factors, including hypotension, vasoactive medications, acute and chronic hypoxia, and ventilation, alter the hemodynamic state of the preterm infant. Additionally, we examine how developmentally linked or acquired dysfunction in cerebral autoregulation contributes to preterm brain injury. In conclusion, we address exciting new approaches to the measurement of autoregulation and discuss the feasibility of translation to the bedside.

The fetus at the tipping point: modifying the outcome of fetal asphyxia

“…2018c, in this issue). Further, potential dysregulation of cerebral autoregulation in sick infants may lead to reduced cerebral perfusion and oxygenation (Vesoulis & Mathur, ). In preterm babies, perfusion and thus oxygenation may be complicated by their immature lungs and by persistent patent ductus arteriosus (Di Fiore et al .…”

“…). Preterm babies may be at risk of loss of cerebral autoregulation leading to impaired cerebral perfusion with low blood pressure (Vesoulis & Mathur, ), and blood flow can fluctuate during events such as seizures. Hypoperfusion is seen in peripheral organs like the gut during seizures in preterm fetal sheep, mediated by sympathetic activity (Bennet et al .…”

NeoDoppler: New ultrasound technology for continuous cerebral circulation monitoring in neonates

“…Currently, NIRS can monitor cerebral oxygenation continuously, and the variations in cerebral oxygenation is used as an indicator of cerebral circulation. Since the first NIRS publication in 1985, 18 NIRS has been considered promising 9,19 and has contributed to increased knowledge about cerebral hemodynamics. 19,20 However, NIRS is still not established as standard monitoring equipment to assess end-organ perfusion, and evidence of improved short-and longterm outcomes with the use of NIRS is still lacking.…”

“…5,6 However, the definition of systemic hypotension and the criteria for treatment of systemic hypotension to prevent low cerebral perfusion is not clear. 5,7,8 Although the focus has changed during the past years from assessment of systemic blood pressure as an indicator of endorgan perfusion to directly assessing end-organ perfusion, 9 the optimal method for direct monitoring of CBF in neonates is lacking. Near infrared spectroscopy (NIRS) enables continuous, non-invasive monitoring of brain oxygenation.…”

Fatores associados às enteroparasitoses em crianças usuárias de creches comunitárias

“…É sabido que o nascimento pré-termo pode acarretar prejuízos à saúde das crianças, como hemorragia intraventricular, hipóxia neonatal e outras intercorrências neurológicas que, de acordo com sua intensidade e duração, podem resultar em sequelas permanentes que vão interferir em diferentes aspectos da vida da criança 29 . Além desses riscos, por razões ainda não elucidadas, neste estudo foi observado que crianças oriundas de uma gestação com duração inferior a 37 semanas apresentaram maior prevalência de enteroparasitoses do que crianças nascidas a termo.…”