| Disturbances in cerebral blood flow (CBF) and impaired Cerebrovascular auto-regulation are important in the pathgenesis of brain injury in premature infant. Trans-cranial Doppler (TCD) has been widely used to study CBF of neonate in NICU. And Near-infrared spectroscopy(NIRS) is a non-invasive monitor of cerebral oxygenation and cerebral hemodynarnics developed recently. Moreover, it can also be used to evaluate the Cerebrovascular autoregulation in the newborn infant. On the basis of experimental research regarding the correlation between NIRS estimations and CBF, TCD and NIRS were used to evaluate cerebral hemodynarnics and autoregulation in preterm infant with or without disease during the 72 hours of age. The study is practical for the clinical use.Part OneCorrelation of NIRS Estimations and Cerebral Blood Flow in Newborn PigletsObjective: To evaluate the correlation of NIRS estimations and cerebral blood flow in newborn piglets, which in turn search out the ideal NIRS estimation reflecting the changes of cerebral blood flow both in hypotension and normal condition. Methods: Ten newborn piglets, aged 1~3 day of age, were randomly assigned to one of the following groups: normal group(n=6) and hypotension group (n=4). Hypotension was induced by withdrawal blood from the artery catheter. CBF was measured with colored microspheres. And CBF was monitored continuously using NIRS. The analysis were performed using linear regression. Results: In the normal group, both AtHb and AHbD were closely correlated with the total brain blood flow and the cortical blood flow. However, they were not correlated with the regional brain blood flow. In the hypotension group, the cerebral blood flow decreased dramatically when the mean artery blood pressure(MABP) dropped to 35 mmHg. HbD was closely correlated with the total brain blood flow, the cortical blood flow and the regional brain blood flow. There was no correlation between AtHb and cerebral blood flow. The difference of the totalIVbrain blood flow, the cortical blood flow and the regional brain blood flow between piglets with or without impaired autoregulation was significant. Conclusion: AHbD was a sensitive marker reflecting cerebral hemodynamic change both in normal and hypotension conditions, while tHb in normal condition. The correlation between HbD and MABP can be used to indicate the state of cerebrovascular autoregulation .Part TwoClinical Study of Cerebral Hemodynamics and Cerebrovascular Autoregulation in Preterm InfantApplication of NIRS on Cerebral Hemodynamics in Premature InfantObjective: To investigate the applied value of NIRS in monitoring cerebral hemo-dynamics and identifying the state of cerebrovascular autoregulation in preterm infant. Methods: Sixty-three premature infants, admitted to our NICU from November 2001 to June 2002, were studied. Of the infants who were enrolled, 22 were preterm without disease (normal group). An additional 41 infants had different disease (14 infants with mild asphyxia, 12 with severe asphyxia, 11 with disease needing ventilation and 4 with other disease). CBF were monitored continuously through the first 3 days in all infants using NIRS. The NIRS estimations and MABP were used to indicate cerebrovascular autoregulation . Cranial ultrasonography was performed to diagnosis brain injury. Results: In normal preterm infants, HbO2, AtHb, and AHbD increased with age. The HbO2, AtHb, AHbD of mild asphyxiated infants were lower than those of normal group at 6 hours of age. The NIRS estimations of severely asphyxiated infants were much lower than those of mild asphyxiated infants. The HbO2 andAHbD in severely asphyxiated infants were higher than normal group and mild asphyxiated infants at 12 and 24 hours of age. Compared to the normal premature infants, NIRS estimations in ventilated infants did not change significantly. According to the correlation between AHbD and MABP, of the 63 premature infants, 13(20.6%) were identified as infants with impaired cerebrovascular autoregulation. The incidence o...
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