Postnatal adaptation of brain circulation in preterm infants

Global and regional postnatal cerebral circulatory changes in stable preter m infants were studied, and their relation to brain injury was assessed. Th irty-five preterm infants were studied on the first and second days of age. Cerebral blood flow (CBF) (mL/hg per min) and cerebral blood volume (CBV) (mL/hg) were measured using near-infrared spectroscopy, The cerebral blood flow velocity (cm/second) (peak systolic, diastolic flow, mean flow) and re sistance index (RI) were determined in the internal carotid, anterior cereb ral, and striate arteries by color Doppler flow imaging. Serial cerebral ul trasound studies were performed to detect changes in brain parenchymal echo genicity or intraventricular hemorrhage (IVH); the maximum severity of thes e findings was considered. CBF and cerebral blood flow velocity increased s ignificantly with time, and such changes were independent of mean blood pre ssure, Po-2, Pco(2), hematocrit, or glycemia. In contrast, CBV and RI remai ned unchanged. According to the results of sonograms, no differences were f ound in postnatal CBF and cerebral blood flow velocity changes, regardless of whether patients had or did not have parenchymal lesions or IVH, However , higher CBV values were found on the second day in infants with IVH compar ed with infants without IVH, Early coupling of CBF and metabolic demands is independent of blood pressure. Improved venous return, instead of vasodila tion, could be important in this adaptation, (C) 2001 by Elsevier Science I nc. All rights reserved.