Phosphorus (31P) spectra from the brains of severely birth-asphyxiated human infants are commonly normal on the first day of life. Later, cerebral energy failure develops, which carries a serious prognosis. The main purpose of this study was to test the hypothesis that this delayed ("secondary'') energy failure could be reproduced in the newborn piglet after a severe acute reversed cerebral hypoxicischemic insult. Twelve piglets were subjected to temporary occlusion of the common carotid arteries and hypoxemia [mean arterial Po, 3.1 (SD 0.6) magnetic resonance spectra from the brains of gas exchange ("birth asphyxia") were commonly normal babies with evidence of critically impaired intrapartum o n the first day of life (1,2). Subsequently, impairment of cerebral energy metabolism developed in some of the Received February 8, 1994; accepted JUIY 7, 1994.

Cerebral perfusion and its relation with systemic circulation in extremely LBW (ELBW) infants in the early neonatal period are not well understood. The cerebral tissue oxygenation index (TOI) and cerebral fractional tissue oxygen extraction (FTOE) were monitored in stable 16 ELBW infants (GA Ͻ29 wk) using nearinfrared spectroscopy (NIRS) at 3-6, 12, 18, 24, 36, 48, and 72 h after birth. The left ventricular end-systolic wall stress (ESWS), left ventricular ejection fraction (LVEF), left ventricular cardiac output (LVCO), and superior vena cava (SVC) flow were also measured simultaneously using echocardiography. The ESWS increased till 18 h and then decreased; LVEF, LVCO, and SVC flow decreased till 12 h and increased thereafter. The TOI decreased till 12 h and correlated with SVC flow; FTOE increased until 12 h and then decreased. These changes in variables of NIRS and echocardiographic measurements contrasted to changes in mean arterial blood pressure (MABP), which showed trends of continuous and gradual increase after birth. We conclude that even stable ELBW infants undergo evident transitional changes in cerebral oxygenation and perfusion in the early postnatal period, which may reflect changes in cardiac function and cardiac output. T he survival rate of extremely LBW (ELBW) infants has markedly improved owing to advances in medical technology and patient management as well as better understanding of neonatal pathophysiology. However, cerebral complications remain a major problem causing long-term neurodevelopmental sequelae (1). Intraventricular hemorrhage (IVH) is known to occur in ELBW infants and is attributable to multiple pathogenetic factors including vulnerability of the vasculature and fragility of the germinal matrix of the brain (2). Hypotension and hypoperfusion of the brain during the immediate postnatal period have been reported to be related with cerebral damage in sick preterm infants (3-5). Kluckow and Evans (6) proposed Doppler echocardiographic measurement of blood flow in the superior vena cava (SVC) as a consistent marker of upper body perfusion, including cerebral blood flow (CBF). They reported that sick preterm infants who developed IVH experienced a period of low SVC flow within the first 48 h of life (7).Although some recent studies have found changes in cerebral oxygenation in very LBW (VLBW) infants (8,9) using near-infrared spectroscopy (NIRS), there have been no studies on longitudinal and detailed assessment of cerebral perfusion in ELBW infants in the early postnatal period. Furthermore, the relationship between cerebral perfusion, systemic perfusion, and arterial blood pressure during the immediate postnatal period is determined by multiple factors and has not been fully understood. The aim of this study was to characterize in detail the cerebral oxygenation and oxygen extraction, as determined by NIRS, and systemic blood flow and cardiac function, as evaluated by echocardiography, in ELBW infants during the early postnatal period. METHODSSubjects. ELBW infants (bir...

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