Cyclic fluctuations in cerebral perfusion and blood pressure have been reported to play a role in the pathogenesis of intracranial haemorrhage in preterm infants. The purpose of this study was to investigate the prevalence and frequency of cycles in CBV with near infrared spectroscopy (NIRS) and to find a correlation with cycles in MAP.Patients and methods: 20 infants requiring mechanical ventilation, haemodynamically stable and not receiving vasoactive drugs, were studied during the first 36 hours of life. Gestational age ranged between 26 and 29 weeks. Deoxygenated, oxygenated and total haemoglobin reflecting CBV were measured with a 4 wavelength instrument (Critikon Oxygenation Monitor 205) in orthogonal mode. MAP was recorded from an umbilical artery catheter with a Statham transducer. Signals were sampled with 2 Hz.Results: All 20 infants showed cyclical variations in CBV and MAP. Fourier analysis revealed two peaks for CBV cycles: one at 1 to 7 min?1 and a second one at 0.14 to 0.2 min?1. MAP fluctuated between 0.2 and 2 cycles min?1. Cerebral pathology included cystic leukomalacia (2 infants), subependymal (3) and intraventricular (9) haemorrhage and did not correlate with the frequency of oscillating signals.Conclusion: Cyclic fluctuations of CBV and MAP seem to be a common phenomenon in preterm infants. Cycles in CBV are independent of cycles in MAP which may be due to auto regulation of cerebral perfusion.
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