Autoregulation of cerebral blood flow and brain lesions in newborn infants

Abstract

These speculations received support from the discovery of proportionality between arterial blood pressure and cerebral blood flow in newborn babies whose clinical condition was unstable. 6 Protective autoregulation of blood flow is one physiological regulatory mechanism that may be disturbed. It maintains constant blood flow over wide ranges of perfusion pressures by arteriolar vasodilation when there is moderate hypotension and by arterolar constriction when there is raised arterial blood pressure. The autoregulatory response is probably a final common pathway for several mechanical, metabolic, and neurogenic processes. It may be abolished by several mechanisms. One is perinatal hypoxia. Studies in fetal and newborn lambs suggest that oxygen saturation at 50% for longer than 10 min results in global abolition of autoregulation for several hours. 7,8 Thus impaired gas exchange across the placenta (eg, in abruption or chorioamnionitis), or across alveoli (eg, in respiratory distress syndrome) are common causes of loss of autoregulation in neonates. Autoregulation seems to be more vulnerable than other regulatory mechanisms for the cerebral circulation. 9