Original articlePostnatal adaptation of brain circulation in preterm infants
Introduction
Coupling between cerebral blood flow (CBF) and metabolic and anatomic development is well characterized in animal neonatal models [1], [2], [3], [4], [5]. In contrast, little information is available on the regulation of the cerebral circulation in the newborn infant. In the human neonate the progression of changes in brain hemodynamics has been assessed mainly by Doppler studies [6], [7], [8], [9], and qualitative information on postnatal cerebral circulatory adaptation has been reported. Nevertheless, early serial quantitative data on brain hemodynamics, particularly in preterm infants, are scarce [10], [11], [12].
Alterations in CBF are associated with the development of hemorrhagic and ischemic lesions in premature infants [13], [14], [15], [16], although no critical value has been defined. Pathologic states may result in altered CBF regulation in neonates [17], [18], [19]. For the postnatal period, attempts have been made to define adverse outcome using certain characteristics of Doppler-derived cerebral blood flow velocity measurements [20], [21], [22]. Nevertheless, most studies of human neonates have focused on Doppler measurements in large cerebral arteries, but changes that occur in small vessels, which are probably more directly involved in brain injury to the premature infant, have not been characterized.
The aim of this study was to analyze adaptative changes in different parameters of brain perfusion in stable preterm infants in the early postnatal period, when most brain lesions occur, using two noninvasive methods. Given the particularities of the distribution of injury depending on maturation, differences in behavior between large and small vessels were of special interest. Finally, we investigated the association between brain damage documented by sonographic criteria and persistent distinctive patterns of brain perfusion.
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Materials and methods
Thirty-five preterm infants with a birth weight of less than 1501 gm each and no major congenital abnormalities admitted to the neonatal intensive care unit at La Paz University Hospital were studied. The oxygenation, ventilation, and hemodynamic condition of all patients were stable. No patient was receiving medication that was likely to affect cerebral circulation. Hemodynamic studies were performed at least 2 hours after treatment in patients who received surfactant therapy. In every study,
Results
Thirty-five preterm infants with a mean gestational age of 29 weeks (range = 26-34 weeks) and mean birth weight of 1,112 gm (range = 650-1500 gm) were included in the study. Thirty-one (88.5%) infants were intubated and mechanically ventilated. Surfactant therapy was administered to 26 infants with hyaline membrane disease.
Overall 24 of 35 infants received NIRS studies, 30 had CDFI studies, and 19 received both NIRS and CDFI studies. The main reason NIRS measurements were unsuccessful was
Discussion
The purpose of this study was to characterize adaptative changes in cerebral hemodynamics in clinically stable preterm infants beyond the immediate postpartum period. Given the difficulties in obtaining repeated suitable NIRS measurements in “healthy” patients, the study had to be restricted to the first 48 hours of age, when most of the study population was on ventilatory support. Nevertheless, as most of the brain lesions documented by CUS occurred in this period, we assume that the findings
Acknowledgements
This work was presented in part at the European Society for Pediatric Research, 1998 Annual Meeting, Belfast, UK. This study was supported by grant from the Fondo de Investigación Sanitaria (FIS 94/0198). The authors thank Rosario Madero, from the Research Unit of La Paz University Hospital, for her valuable help with statistics.
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