Original articleCerebral hemodynamics during early neonatal period in preterm infants with periventricular leukomalacia
Introduction
Full-term asphyxiated infants exhibit a state of vasoparalysis and hyperemia. Measurements of cerebral blood flow velocity by Doppler ultrasonography have shown an increase in mean flow velocity with decreased resistance index in full-term infants with hypoxic-ischemic encephalopathy within a few days after the insult [1], [2], [3]. An increase in cerebral blood volume has been revealed by near-infrared spectroscopy [4], xenon-133 clearance [5] or positron emission tomography [6]. These changes are correlated with the degree of brain injury.
On the other hand, the relation between cerebral blood flow and brain injury in preterm infants has not been fully elucidated. Some authors reported that cerebral blood flow measured by xenon-133 clearance was lower in non-surviving infants but there was no correlation with later neurological outcome [7]. Meek et al. described that cerebral blood flow measured by near infrared spectroscopy was lower in infants with germinal matrix-intraventricular hemorrhage than those without hemorrhage, despite no difference in carbon dioxide tension and a higher mean arterial blood pressure [8]. A recent study using near infrared spectroscopy demonstrated that impaired cerebrovascular autoregulation was associated with a high likelihood for occurrence of severe germinal matrix-intraventricular hemorrhage and/or periventricular leukomalacia (PVL) [9].
There have been several reports on the association between hypocarbia and the occurrence of PVL [10], [11], [12], [13], [14], [15], [16]. This association was explained by the speculation that cerebral vasoconstriction and decreased cerebral blood flow could be induced by hypocarbia. However, the relation between cerebral blood flow and hypocarbia has not yet been fully determined.
The aim of this study is to prospectively elucidate the relation among cerebral blood flow, periventricular leukomalacia and hypocarbia using Doppler ultrasonography.
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Patients and methods
One hundred and sixty-one infants with gestational age between 27 and 34 weeks were born at Anjo Kosei Hospital between 1996 and 1997. Six infants who died during early neonatal period were excluded from this study because the presence or absence of neurological sequelae was difficult to evaluate. Fifty-five of the remainder required mechanical ventilation during the first 72 h of life. Two infants who required unusually high ventilator settings because of pulmonary hemorrhage were excluded
Results
The gestational age and birth weight in PVL group was 30.1 weeks and 1523 g, respectively (Table 1). The gestational age and birth weight in control group was 30.1 weeks and 1464 g, respectively (Table 1). There was no significant difference in gestational age or birthweight between the two groups. The mean arterial blood pressure was maintained above 35 mmHg in all infants throughout the study period. Oxygenation was appropriately maintained with SaO2 value between 93 and 99%.
The EEG
Discussion
Our study demonstrated that a reduced RI in infants with PVL during the first 72 h of life. This suggests that cerebral arteries may be rather paralytic in infants with PVL. The presence or absence of hyperemia in infants with PVL is uncertain because MV was not significantly different between infants with and without PVL. These results imply that cerebral blood flow volume in infants with PVL will be at least the same as those without PVL. Although ischemia is an important factor for the
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