CROSS-SPECTRAL ANALYSIS OF CEREBRAL AUTOREGULATION DYNAMICS IN HIGH-RISK PRETERM INFANTS DURING THE PERINATAL-PERIOD

In preterm infants intraventricular hemorrhage occurs predominantly wi thin the perinatal period, which may be due to a ''lost autoregulation '' of cerebral blood flow (CBF). In this study, perinatal autoregulati on dynamics were investigated in high risk preterm infants by cross-sp ectral analysis (CSA), which is a statistical tool in the analysis of time series. In 15 ventilated preterm infants of 25-32 gestational wee ks, a total number of 30 records were made between 24 and 96 h of life . Doppler-derived CBF velocity (CBFv), used as a quantitative measure for CBF, and direct mean arterial blood pressure (MABP) were measured continuously for 10 min. The spectral power of low frequency (LF, 0.02 -0.2 Hz) oscillations in CBFv and MABP was quantified by spectral anal ysis. From the results of CSA, a LF phase-shift between the CBFv and M ABP LF oscillations was calculated in each record. Within the study gr oup, the LF spectral power of CBFv and MABP was initially low and incr eased significantly until 96 h of life. The LF phase-shift was about 0 degrees at 24 h and increased significantly to 55 degrees at 96 h of life. The initially low LF spectral power of CBFv and MABP may indicat e a perinatal depression of autonomic nervous centers, which are thoug ht to control LF oscillations of vital parameters. In the light of a h igh pass filter model for autoregulation, the initially low LF phase-s hift may indicate an initially impaired autoregulation, which supports the ''lost autoregulation'' hypothesis.